Translator

Bob McDavitt's ideas for sailing weather around the South pacific

28 December 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 28 December 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

The Ocean: extra heat has been stored in the Pacific Ocean for a while now
and all the Oceanic indices have crossed the threshold into El Nino
territory.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) for much of September, and again for a week in November,
then relaxed in early December, but last week started another negative dive.
The atmospheric El Nino is stuttering.
In an El Nino event the latitudes of the normal weather zones are drawn
closer to the equator, causing the South Pacific Convergence zone to shift
further north and east of its normal position.

TROPICAL TOPICS
The tropical low that formed last Wednesday between Samoa and
Rarotonga/Tahiti has travelled SE and faded.
Rain intensified in the South Pacific Convergence Zone last week. It also
reached deluging levels over Sri Lanka (with the arrival of a tropical Low)
and over Malaysia (as a monsoon---the most intense in decades).
Also at present there is a tropical depression situated east of Philippines,
travelling west, also TC KATE to SW of Cocos Island in the South Indian
Ocean.
And in the South Pacific another tropical low has formed today, just east of
Samoa. The latest thinking is that this South Pacific system may soon move
SSE with slight intensification getting close to Niue/Rarotonga by local
Monday.

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W ISSUED
FROM RSMC NADI Dec 28/0126 UTC 2014 UTC.
TROPICAL DEPRESSION TD05F CENTER [1000HPA] ANALYSED NEAR 13.0S 169.0W AT
280000UTC. TD05F SLOW MOVING. POSITION POOR BASED ON MTSAT IR/VIS IMAGERY
AND PERIPHERAL OBSERVATIONS. SST AROUND 30 DEGREES CELSIUS.
CONVECTION REMAINS PERSISTENT IN THE PAST 06 HOURS. ORGANISATION REMAINS
POOR. THE SYSTEM LIES UNDER AN UPPER DIFFULENT REGION IN A MODERATE SHEARED
ENVIRONMENT. OUTFLOW GOOD TO THE SOUTHEAST. CYCLONIC CIRCULATION EXTENDS UP
TO 500HPA.
GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT SOUTHEASTWARDS WITH SLIGHT
INTENSIFICATION.
POTENTIAL FOR TD05F TO DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 24 TO 48
HOURS IS LOW.
NO OTHER SIGNIFICANT TROPICAL DISTURBANCE ANALYSED OR FORECAST IN THE AREA.
Fiji Met Service tropical disturbance discussion above is as at
http://www.met.gov.fj/aifs_prods/20036.txt
If you are in this area then please remain vigilant and keep up to date with
these latest TC bulletins.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is strong east of the dateline with strong NW winds on its northern
side, strong SE winds on its southern side and gale force squalls in-
between. A new branch is expected to form over Coral Sea from mid-week.

STR= Sub-tropical Ridge
A new High cell is crossing the South Island tonight and is expected to
merge with the quasi-stationary high near 40S 170W by mid-week, making a
larger High centered near 45S. This High should then travel east for the
remainder of the week along 45S.
The next High is expected to enter the central Tasman Sea on Wed/Thu and
fade on Friday. Another High is expected to cross Tasmania on Thursday and
then move east crossing central NZ over Sat 3/Sun 4 Jan. Good by then for
holiday weekenders.

Over NZ
Trough between Highs is expected to reach central Tasman by Tuesday and
cross NZ on Wednesday in time for local New Year s Eve. This should be
followed by a period of disturbed SW/S winds and fronts on Thursday and
Friday.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe:
send a reply email saying LEAVE.

23 December 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 24 December 2014
Bob McDavitts ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

I want to offer the best of greetings and good things to you and yours for
Christmas and the Yule-tide season.
This extra blog from me gives me the opportunity to update you with that
tropical low between Samoa and Tahiti as seen at
http://www.meteo.pf/observation.php?carte=pf
and at http://www.met.gov.fj/aifs_prods/0640.gif

The latest thinking about this feature is as follows:
>>>>
TROPICAL DISTURBANCE ADVISORY NUMBER A5 ISSUED FROM RSMC NADI Dec 23/1939
UTC 2014 UTC.
TROPICAL DEPRESSION 03F CENTER [999HPA] ANALYSED NEAR 13.8S 158.8W AT
231800UTC. DEPRESSION MOVING EAST AT ABOUT 06 KNOTS. MAXIMUM 10-MINUTE
AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 30 KNOTS.

OVERALL ORGANISATION HAS IMPROVED PAST 24 HOURS. DEEP CONVECTION HAS
INCREASED AND IS OVER THE EASTERN SEMI CIRCLE OF LLCC. SYSTEM LIES UNDER A
STRONG UPPER DIVERGENT REGION IN A LOW TO MODERATE SHEARED ENVIRONMENT.
OUTFLOW GOOD TO THE EAST AND NORTH BUT RESTRICTED ELSEWHERE. CYCLONIC
CIRCULATION EXTENDS UP TO 500HPA. SST AROUND 29 DEGREES CELCIUS. DVORAK
ANALYSIS BASED ON 0.4 WRAP GIVING DT=2.5, MET AND PT AGREE. FT BASED ON DT
THUS YEILDING T2.5/2.5/D0.5/24HRS.

GLOBAL MODELS AGREE ON A EASTERLY MOVEMENT THEN SOUTHEAST WITH FURTHER
INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE WITHIN THE NEXT
12 TO 24 HOURS IS MODERATE TO HIGH.

FORECASTS:
AT 12 HRS VALID 240600 UTC 14.2S 158.1W MOV ESE AT 04KT WITH 35 KNOTS CLOSE
TO CENTRE AT 24 HRS VALID 241800 UTC 15.2S 157.5W MOV SE AT 05KT WITH 40
KNOTS CLOSE TO CENTRE
OUTLOOK:
AT 36 HRS VALID 250600 UTC 16.4S 157.3W MOV SSE AT 06KT WITH 45 KNOTS CLOSE
TO CENTRE AT 48 HRS VALID 280600 UTC 17.6S 157.3W MOV S AT 06KT WITH 45
KNOTS CLOSE TO CENTRE

THE NEXT TROPICAL DISTURBANCE ADVISORY ON TD03F WILL BE ISSUED AT OR AROUND
240200UTC.
>>>>>>>>>>>>>
Updates on this Disturbance summary as seen at
http://www.met.gov.fj/aifs_prods/20032.txt
SO it is expected to go east then SE and may develop more and get named as a
tropical cyclone by Christmas Day.
If you are in the Tahiti/Southern Cooks area, then I recommend vigilance.

bob

Bob Blog

WEATHERGRAM
YOTREPS
Issued 24 December 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

I want to offer the best of greetings and good things to you and yours for
Christmas and the Yule-tide season.
This extra blog from me gives me the opportunity to update you with that
tropical low between Samoa and Tahiti as seen at
http://www.meteo.pf/observation.php?carte=pf
and at http://www.met.gov.fj/aifs_prods/0640.gif

The latest thinking about this feature is as follows:
>>>>
TROPICAL DISTURBANCE ADVISORY NUMBER A5 ISSUED FROM RSMC NADI Dec 23/1939
UTC 2014 UTC.

TROPICAL DEPRESSION 03F CENTER [999HPA] ANALYSED NEAR 13.8S 158.8W AT
231800UTC. DEPRESSION MOVING EAST AT ABOUT 06 KNOTS. MAXIMUM 10-MINUTE
AVERAGE WINDS NEAR THE CENTRE ESTIMATED AT ABOUT 30 KNOTS.

OVERALL ORGANISATION HAS IMPROVED PAST 24 HOURS. DEEP CONVECTION HAS
INCREASED AND IS OVER THE EASTERN SEMI CIRCLE OF LLCC. SYSTEM LIES UNDER A
STRONG UPPER DIVERGENT REGION IN A LOW TO MODERATE SHEARED ENVIRONMENT.
OUTFLOW GOOD TO THE EAST AND NORTH BUT RESTRICTED ELSEWHERE. CYCLONIC
CIRCULATION EXTENDS UP TO 500HPA. SST AROUND 29 DEGREES CELCIUS. DVORAK
ANALYSIS BASED ON 0.4 WRAP GIVING DT=2.5, MET AND PT AGREE. FT BASED ON DT
THUS YEILDING T2.5/2.5/D0.5/24HRS.

GLOBAL MODELS AGREE ON A EASTERLY MOVEMENT THEN SOUTHEAST WITH FURTHER
INTENSIFICATION.

POTENTIAL FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE WITHIN THE NEXT
12 TO 24 HOURS IS MODERATE TO HIGH.

FORECASTS:
AT 12 HRS VALID 240600 UTC 14.2S 158.1W MOV ESE AT 04KT WITH 35 KNOTS CLOSE
TO CENTRE AT 24 HRS VALID 241800 UTC 15.2S 157.5W MOV SE AT 05KT WITH 40
KNOTS CLOSE TO CENTRE

OUTLOOK:
AT 36 HRS VALID 250600 UTC 16.4S 157.3W MOV SSE AT 06KT WITH 45 KNOTS CLOSE
TO CENTRE AT 48 HRS VALID 280600 UTC 17.6S 157.3W MOV S AT 06KT WITH 45
KNOTS CLOSE TO CENTRE


THE NEXT TROPICAL DISTURBANCE ADVISORY ON TD03F WILL BE ISSUED AT OR AROUND
240200UTC.
>>>>>>>>>>>>>
Updates on this Disturbance summary as seen at
http://www.met.gov.fj/aifs_prods/20032.txt
SO it is expected to go east then SE and may develop more and get named as a
tropical cyclone by local Christmas Day.
If you are in the Tahiti/Southern Cooks area, then I recommend vigilance.

bob

21 December 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 21 December 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

The Ocean: extra heat has been stored in the Pacific Ocean for a while now
and all the Oceanic indices have crossed the threshold into El Nino
territory.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) for much of September, and again for a week in November,
but has since been relaxing again--- the atmospheric El Nino is stuttering

In an El Nino event the latitudes of the normal weather zones are drawn
closer to the equator, causing the South Pacific Convergence zone to shift
further north and east of its normal position.

TROPICAL TOPICS
Weekly rain maps over the past fortnight show an increase in convection over
the past week east of 180 and another increase to NE of Madagascar in the
western South Indian Ocean.
A MJO (Madden Julian Oscillation of enhanced convection) is now fading near
and just east of 180 after it made its way eastwards across the Coral Sea
last week.
This has allowed a zone of near equatorial westerly winds to extend along
5 to 15S as far east as Samoa. These near equatorial westerly wind tend to
upset the wets facing harbours in Tuvalu and Tokelau.
These west or NW winds also accentuate the convection in the South Pacific
Convergence zone, and help tropical depressions to form.
One is forming now east of Samoa and north of Niue:
It has strong NW winds on its NE side and strong SE winds on its SW side The
latest thinking is that this system may soon move SE to the area between
Rarotonga and Tahiti by Christmas Day:

Tropical Disturbance Summary For area Equator to 25S, 160E to 120W ISSUED
FROM RSMC NADI Dec 20/2347 UTC 2014 UTC.
TROPICAL DISTURBANCE 03F CENTER {[1004HPA]} ANALYSED NEAR 13.2S 170.0W AT
202100UTC. TD03F SLOW MOVING. POSITION POOR BASED ON MTSAT VIS/IR IMAGERY
AND PERIPHERAL OBSERVATIONS. SST AROUND 30 DEGRESS CELCIUS.
ORGANISATION IS POOR. CONVECTION IS PERSISTANT IN THE NORTHERN SEMICIRCLE
AND DETACHED FROM SUPPOSED LLCC IN THE PAST 06 HOURS. THE SYSTEM LIES IN A
DIFFULENT REGION, EAST OF A SHORTWAVE UPPER TROUGH IN A LOW SHEARED
ENVIRONMENT. CYCLONIC CIRCULATION EXTENDS UPTO 500HPA.
GLOBAL MODELS HAVE PICKED THE SYSTEM AND MOVE IT EAST-SOUTHEASTWARD WITH
LITTLE INTENSIFICATION.
POTENTION FOR TD03F TO DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 24 TO 48
HOURS IS LOW.
NO OTHER SIGNIFICANT TROPICAL DISTURBANCE ANALYSED OR FORECAST IN THE AREA.
Fiji Met Service tropical disturbance discussion above is as at
http://www.met.gov.fj/aifs_prods/20036.txt
If you are in this area then please remain vigilant and keep up to date with
these latest TC bulletins.

MJO cycles are usually paced about 6 weeks apart and are known to increase
the risk of tropical cyclone formation as they pass. This MJO is this week
bothering places east of 180. My take on this is that for the next few weeks
the Southwest pacific will be between MJO events and the risk of enhanced
convection/tropical disturbances will drop to LESS THAN NORMAL by New Year
and stay that way for a few weeks. Thats good news.

WEATHER ZONES
Note that there are expected to be STRONG NE winds near and north of the
equator, making a E swell there over 2.5 significant metres.

SPCZ=South Pacific Convergence zone.
SPCZ is strong east of the dateline with strong NW winds on its northern
side, strong SE winds on its southern side and gale force squalls in-
between. Avoid.

STR= Sub-tropical Ridge
Finally, after several weeks, a High is expected to get east of central NZ
on Monday. This HIGH should expand to over 1030 hPa and move slowly NE
across Chatham Islands on Tuesday and NE to 35S 165W by Sun 28 Dec.

Over NZ
Next main trough is expected to reach SW of South Island on Boxing Day and
spread NE (and weaken) to northern NZ by Sat/Sun 3/4 January.
Nice Holiday weather over northern NZ (albeit NE winds from 23 to 30 Dec),
but try and avoid sailing during the weekend of 3 and 4 Jan.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz

Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe from
WordPress: click the "unsubscribe" link on the bottom of the email.
Or, if email wasn't from WordPress then send a reply email saying LEAVE.

14 December 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 14 December 2014
Bob McDavitts ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

The Ocean: extra has been stored in the Pacific Ocean for a while now and
all the Oceanic indices have crossed the threshold into El Nino territory.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, and again for a week in November, but has since been
relaxing again the atmospheric El Nino is stuttering In an El Nino event
the latitudes of the normal weather zones are drawn closer to the equator,
causing the South Pacific Convergence zone to shift further north and east
of its normal position.

TROPICAL TOPICS
A MJO (Madden Julian Oscillation of enhanced convection) is making its way
now eastwards across the South Pacific Ocean this week, and this has formed
near-equatorial west/NW winds over northern Australia and in the northern
Coral Sea. These may reach 180 in the next week or so, making for
challenging conditions for fishing and diving in Tuvalu and Kiribati.
MJO cycles are usually paced about 6 weeks apart and are known to increase
the risk of tropical cyclone formation as they pass. This MJO has triggered
a small Tropical Cyclone over the open sea to SW of Indonesia called BAKUNG
near 9S 87E. However this MJO is early in the season and is NOT expected to
form a TC in the Pacific.

Weekly rain maps over the past fortnight show an increase in convection over
the past week spreading eastwards across Northern Australia. Also the rain
that was over Philippines with HAGIPUT about a week ago has gone now.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is now split into several distinct convergence zones, and this makes
the next week more volatile than normal. The MJO does this, but I think this
MJO might not trigger a TC in our region. That just raises the ante for the
next MJO, which is likely in January. I suppose thats good news for
Christmas /New Year travellers.
The MJO has triggered a series of sub-tropical troughs in the northern
Tasman SeaOne is passing by northern NZ tonight and gave wind and rain here
for past 24 hours, upsetting our Christmas in the Park in Auckland last
night and cancelling at least one local youth group picnic today.
Yuck. But it is a sign of summer, I suppose.
After this week there should be two Convergence Zones: One visiting New
Caledonia and Fiji for Christmas and another, likely to be intense, between
Samoa and Southern Cooks/ French Polynesia. Disturbing Christmas weather
here.

STR= Sub-tropical Ridge
The troughs forming in the northern Tasman Sea have dislodged the STR to
southern NZ (first time in weeks, a nice change for them). One High is
expected to move off to NE of NZ over next few days as another Low crosses
the Tasman Sea from Thursday to Sunday 21st (over South Island).
This should set things up so that next HIGH crosses central Tasman Sea 40S
from Sunday to Wednesday (fading over North Island) and the following HIGH
travels along 45S from Wed crossing central NZ on Friday/Saturday.
Happy settled weather for Christmas to NZ.

Over northern NZ
Strong East/NE/NW winds on Monday/Tuesday/Wednesday from passing trough,
then quieter northerly winds until a weak trough is expected on Sun/Mon
21/22 Dec, and then SE winds.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe
send a reply email saying LEAVE.

07 December 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 07 December 2014

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, relaxed for a while in October, and dived below -
10 early in early November, and is now hovering near -10.

We know that in an El Nino event the latitudes of the normal weather zones
are drawn closer to the equator, causing the South Pacific Convergence zone
to shift further north and east of its normal position.

TROPICAL TOPICS
Typhoon HAGUPIT is tonight moving NW across northern Philippines. Just over
a year and a month after HAIYAN.
Usually December is a quiet month for cyclones in the NW Pacific, however
another tropical system is expected to form near 5N 140E by Tuesday and
deepen as it passes near Yap on Wednesday/Thursday and then deepen further
until it is expected to visit northern Philippines next Sunday, one week
after HAGIPUT. However if this system takes a track similar to HAGIPUT then
it may encounter cooler conditions in the recently stirred surface waters
and thus not intensify as much. We hope.

Weekly rain maps over the past fortnight show an increase in convection over
the past week spreading eastwards from Indonesia to Micronesia. This
increase in convection is associated with what is called an MJO or Madden
Julian Oscillation, and has helped trigger and fire up HAGIPUT and may
trigger a few more tropical lows in the Micronesian area during the next two
weeks.
This increase in convection may well gradually make its way into the Pacific
Ocean over the next few weeks. By mid-December this is expected to increases
the risk of a tropical cyclone generating in the area north of Vanuatu.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to take a week off over PNG and Solomon Islands and be
strong from northern Vanuatu to Wallis/Futuna to Samoa to Southern Cooks.
>From the end of this week there is likely to be an increase in activity
around Australia and in the area about and north of Vanuatu.

STR= Sub-tropical Ridge
The STR has split into a strong zone well to the south from Aussie Bight
to south Tasman Sea, and a northern zone lingering at 30S between NZ and
Niue.
The northern High is expected to slowly travel east to southeast between
30S and 35S as a low deepens between the Highs in the Tasman Sea by
Thursday local.

Over northern NZ
Brief ridge is expected to cross northern NZ on Monday with light winds,
followed by a N/NW flow on Tuesday to Friday (as low develops in Tasman
Sea) and then an associated front on Saturday, followed by a brief cool
southwest flow on Sunday 14 Dec, and then light winds in a ridge on
Monday 15 Dec.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at
bottom right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com
To unsubscribe send a reply email saying LEAVE.

30 November 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 30 November 2014
Bob McDavitts ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

I've just been introduced to another website presenting the weather data in
an interesting way http://www.meteoearth.com/

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, relaxed for a while in October, and dived below -
10 early in early November, but is now relaxing again.
We know that in an El Nino event the latitudes of the normal weather zones
are drawn closer to the equator, causing the South Pacific Convergence zone
to shift further north and east of its normal position.
Well, as November draws to a close we can look at the average weather map
mid-month, thanks to NOAA and this shows Highs have been stronger than
normal in the north Tasman sea, and just south of South Africa, and lows in
the southern ocean have been deeper and more north than normal in south
Indian Ocean, and to SE of NZ, and to SE of South America. The extra highs
in north Tasman Sea and lows to SE of NZ have combined to give extra SW
winds over NZ.

NIWA have issued a news release about New Zealand's November weather at
http://www.scoop.co.nz/stories/SC1411/S00083.htm they say there has been
more SW winds than normal over New Zealand during November. The rainfall, as
measured by the SPI (Standardized Precipitation Index) has been close to
normal in most places but the extra SW winds show as patches of extra
rainfall in the W and south of the South Island.

The extra SW winds are causing soils to dry out faster than normal in
eastern North island places from Northland thru Coromandel and Bay of Plenty
to Gisborne/Hawkes Bay/and the southern quarter of the North Island, and the
eastern South Island.

They also say, and I quote It should be noted that this rainfall pattern is
commonly associated with El Nino events and while El Niqo has not been
officially declared, it may be an indication that such an event is
imminent.

TROPICAL TOPICS
Last weekend Cyclone Adjali was the first of the new season in the Indian
Ocean and was heading towards Mauritius before it weakened. The Volvo Race
fleet diverted clockwise around another system now near 20S 60E and one of
fleet, Sailing Vessel Team Vestas Wind, ended up sailing onto a reef (at
night) in the Cargados Carajos Shoals around 400 km to northeast of
Mauritius. Ouch.

At present the remains of Cyclone SINLAKU are fading over China.
Another area of interest is developing in the NW Pacific and is expected to
become a Cyclone over Micronesia by Tuesday and travel west towards
Philippines late this week.

There are a couple of areas of interest in the Indian Ocean, one near 20S
60E and another near 11S 90E  I suppose we can declare the Southern
Hemisphere cyclone season to now be officially open.

Weekly rain maps over the past fortnight show an increase in convection over
the past week in the Indian Ocean and in the zone from north of Solomon
Island along to Samoa. There was flooding in Samoa early last week, but the
feature responsible then faded as forecast in last weeks Weathergram.

This increase in convection in the Indian Ocean is possibly part of a MJO
cycle that will gradually make its way into the Pacific Ocean over the next
few weeks. By mid December this is expected to increases the risk of a
tropical cyclone generating in the area north of Vanuatu.


WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ may not be as strong as it was last week, and is expected to be located
near the north end of its normal range, stretching from north of Solomon
island to northern Vanuatu and the east across Tuvalu to Samoa/Tokelau, with
scattered convection also over French Polynesia.
A burst of northerly swell reaching 2 to 3metres is expected to spread south
and east over the next few days  it should be most noticeable about and
just north of the SPCZ and roughen the sea there. Not the best for good
diving or fishing between northern Vanuatu and Samoa this week.

STR= Sub-tropical Ridge
The STR is also strong and well defined and mostly at its normal latitude
for the time of year, but now north of normal in zone east of NZ. It has
been north of normal in the NZ area but is expected to be closer to normal
latitude this week as the HIGH tonight in the south Tasman Se is expected to
travel NE across the North Island on Tuesday night/Wednesday and then be
slow-moving off the NE of NZ until next week, so that approaching troughs
stall in the Tasman Sea.
HIGH near 35S 130W, to the south of Pitcairn Island, is expected to be
slow-moving and peak in intensity over 1032 hPa by Tuesday UTC and is
expected to stay put until Wednesday and then slowly weaken and move NE.
There are likely to be strong easterly and NE winds on the northern side of
this high, especially between 15 and 20S until Friday.

Between the tropics and NZ
Good weather this week for sailing from the tropics to NZ.
No good arriving on Monday 1 December because thats when a cold trough is
expected to cross the North Island. Then there is an easterly flow expected
on the north side of the high that is expected to cross the North Island on
Tuesday night/Wednesday.
After Wednesday there is expected to be a useful N to NW flow over northern
NZ, good for arrival. This NW flow may get strong and unsettled on Tuesday 9
December, as a trough travels east across southern NZ. The NW flow should be
Ok again on Wednesday 10 Dec for arrival, and then northern NZ may become
unsettled as troughs start to arrive from the Tasman Sea.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe,
send a reply email saying LEAVE.

23 November 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 23 November 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardized difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, slightly relaxed for a while in October, and dived below
-10 early in November, but is now relaxing a little.

TROPICAL TOPICS
Tropical cyclone activity has now reduced to one possible area in the Indian
Ocean, and an area of interest to the NW of Samoa.

The latest tropical disturbance summary at www.usno.navy.mil/NOOC/nmfc-
ph/RSS/jtwc/ab/abpwweb.txt
has this to say about this system:
ABPW10 PGTW 230600
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/SIGNIFICANT
TROPICAL WEATHER ADVISORY FOR THE WESTERN AND /SOUTH PACIFIC
OCEANS/230600Z-240600ZNOV2014// RMKS/ 1. WESTERN NORTH PACIFIC AREA (180 TO
MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY: NONE.
2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 8.2S 177.1W, IS NOW
LOCATED NEAR 11.5S 174.4W, APPROXIMATELY 204 NM NORTH OF PAGO PAGO, AMERICAN
SAMOA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS UNORGANIZED FLARING
CONVECTION ASSOCIATED WITH AN ELOGATED LOW-LEVEL CIRCULATION CENTER. A
230354Z NOAA-19 MICROWAVE IMAGE REVEALS VERY FRAGMENTED CONVECTIVE BANDING
ON THE EASTERN SIDE BROADLY WRAPPING INTO THE CENTER. ALSO, A CIMMS 230300Z
850MB RELATIVE VORTICITY PRODUCT SHOWS AN ELONGATED VORTICITY SIGNATURE.
UPPER-LEVEL ANALYSIS INDICATES THE DISTURBANCE IS LOCATED NORTH OF THE RIDGE
AXIS IN A FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (05 TO 15 KNOT)
VERTICAL WIND SHEAR AND EXCELLENT POLEWARD OUTFLOW.
ADDITIONALLY, SEA SURFACE TEMPERATURES WITH A RANGE OF 26 TO 28 DEGRESS
CELCIUS IN THE AREA ARE FAVORABLE FOR DEVELOPMENT. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.
(2) NO OTHER SUSPECT AREAS.//

It is judged as having a low chance of any further deepening. The GFS
models and their GRIB files are picking that this system may deepen into a
depression on Mon/Tuesday and bring clockwise gale winds between the Niuas
and Niue, then Southern Cooks on Wednesday/Thursday- but the more reliable
ECMWF model suggests this isn't likely.

Weekly rain maps over the past fortnight show an increase in convection over
the past week in the Indian Ocean. This is possibly part of a MJO cycle
that will gradually make its way into the Pacific Ocean over the next few
weeks. For the next week or so, it increases the risk of a tropical cyclone
formation in the area to NW of Aussie. For the following weeks this
increased risk spreads east. This is shown at
www.meteo.nc/cyclone/coin-des-experts

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ has strengthened in the past week and is expected to drift south onto
northern Tonga and SE onto NIUE, then later onto southern cooks.
The GFS model is picking that a depression may form on the SPCZ and move
along it to the SE, but other models only have a weak feature. The GFS
model also has a tropical low forming SE of French Polynesia. These may not
actually happen but if you are sailing in these areas this week then brace
for strong winds anyway.

STR= Sub-tropical Ridge
The STR is strong and well defined and mostly at its normal latitude for the
time of year, but north of normal in the Tasman Sea/ NZ area.
HIGH at 30S between New Caledonia and New Zealand is expected to stay put
until Wednesday and then slowly fade away as it travels east from Thursday
to Saturday.
NEXT High cell is expected to travel east along 45S from Saturday 29 Nov ,
reaching North island around Wed 3 December - followed by a northerly flow
-that is GOOD for arriving in NZ  late next week (Thursday to Saturday 4-6
Dec).

Between the tropics and NZ
At North Minerva:
Trade winds until Thursday, light and variable on Fri 28 to Mon 1 Dec, then
more trade winds. Good idea to depart around Thursday so as to catch a
northerly flow when approaching NZ  voyage will encounter a period of
southerly winds around Sun 30 Nov/Mon 1 Dec and requires waypoints.

Over northern NZ:
Westerly flow on Monday/Tuesday, then an active trough on Wednesday followed
by a SW/S flow on Thursday 27 to Tues 2 Dec. NOT the best week (after
Tuesday) for arriving in NZ.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
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16 November 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 16 November 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, slightly relaxed for a whole in October, and is now
diving below -10 again. If this index remains below -10 for more than a
month then this will the start of a full blown El Nino episode.

The Ocean
The amount of heat that is being stored in the sea in the Eastern Equatorial
pacific has also increased, as measured by the NINO3.4index.
This indicates that the atmosphere and the ocean are in cahoots.

TROPICAL TOPICS
There are no tropical cyclones around at present: Tropical cyclone activity
has now reduced to just one possible depression area in the Indian Ocean.
Weekly rain maps over the past fortnight show less rain around in the past
week than the previous week.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ has weakened in the past week but is expected to intensify this week
and slowly drift south. It is possible (but models are not yet in
agreement) that a tropical depression may form over Tokelau by Friday 21 Nov
and then move SE across Samoa and near Niue over following few days.

STR= Sub-tropical Ridge
The STR is strong and well defined and north of normal at present (all El
Nino traits).
HIGH between Tonga and NZ at present is expected to travel east along 30/35S
as it peels off to east of 140W by Thursday. Light winds at Minerva from
Monday to Wednesday.
A new HIGH is expected to travel into the Tasman sea around 30S on Mon/Tue
/Wed and then travel east along 30/35S across and to east of NZ on
Thu/Fri/Sat/Sun/Mon 20/21/22/23/24 Nov.

Between the tropics and NZ
At north Minerva:
Light winds in a ridge are expected until Wednesday, then trade winds are
expected to return for the next week or more, good for sailing to NZ.

Over northern NZ:
There is a disturbed westerly flow until Wednesday, and then a slowly
passing High from Thu 20 to Mon 24 Nov, then a passing trough, around Tue
25 Nov , then another passing High from on Wed/Thu 26/27 Nov, and then an
unsettled period with a trough on Fri/sat/ Sun 28/29/30 Nov .
Try and use this to time your arrival in NZ to be in settled weather.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe:
send a reply email saying LEAVE.

09 November 2014

Bob Blog

WEATHERGRAM
YOTREPS

Issued 09 November 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, slightly relaxed for a whole in October, and is now
diving more negative again.

The Ocean
The amount of heat that is being stored in the sea in the Eastern Equatorial
pacific has also increased, as measured by the NINO3.4index.

The chances of a full blown El Nino episode over the next few months are now
considered to be no more than 58% (less than this time last month).

TROPICAL TOPICS
Tropical cyclone activity has now reduced to a few possible potential areas.

Weekly rain maps over the past fortnight show some local regions of intense
rain due to a few tropical cyclones. There also has been a notable build-up
of convection in the past week between India and Indonesia. Not much change
in South Pacific.


WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is steady in position and fluctuating in intensity. Mainly over the sea
between Solomons and Wallis /Futuna then along 15S.
The Low that has formed between Fiji and New Zealand near 25/30S 180 is
expected to travel SE and fade-away by Wednesday.
A Low is expected to form near 30S 140W by Tuesday and then travel to east
then south east.

STR= Sub-tropical Ridge
High is expected to cross Tasmania on Tuesday and then travel NE towards 20S
between New Caledonia and Kermadecs by the end of the week, bringing a zone
of light winds.

Between the tropics and NZ
At north Minerva a front visited on Saturday accompanied by squally showers
and strong E/NE winds. As the Low in the region travels east/southeast over
the next few days, expect strong WNW winds there from Monday morning to
Tuesday morning, peaking pre-dawn on Tuesday. Then expect moderate SW winds
there on Tuesday and Wednesday. After that the STR is expected to get north
of Minerva for a few days so that it has W/SW/S winds on Thursday and
Friday, finally reverting to SE this weekend.

An intensifying trough is expected to cross NZ on Monday and Tuesday,
followed by an outbreak of strong to gale SW winds in the Tasman Sea on
Wednesday and Thursday. These winds are expected to help propagate an area
of big SW swells (from the Southern Ocean) that spread NE into the region
between NZ and Fijias far north as 25S on Thursday and 23S on Friday.

Voyages from New Caledonia /Fiji/Tonga to New Zealand should wait for the
Low to go away by late Tuesday, and then try and avoid the big swells on
Thursday /Friday. This can be done with a Friday departure and a few
waypoints.

AT this stage, the outlook next week over NZ looks reasonable for voyages
aiming to arrive there between Tue 18 and Friday 21st ( but this may
change).

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe:
send a reply email saying LEAVE.

03 November 2014

Bob Blog extra

WEATHERGRAM
YOTREPS
Issued 04 November 2014

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world Special edition aimed at those at the Minerva Reef yacht
club

DEPART BEFORE 1pm WEDNESDAY

This morning most (not all) computer models are picking that a tropical
trough may trigger the development of a low near 25S 175E ( south of
Fiji) on Sunday 9 Nov, and this low may then travel east for a few days
pushing a front with strong to gale NE winds over Minerva by late Sunday and
forming a squash zone of easterly gales near 30S 18 on Sunday/Monday.

This scenario still has only around 66% chance of actually happening, but
its likely impact is worth avoiding. To do so , anyone at Minerva should
depart for NZ by around noon Wednesday ( and those in Tonga should now stay,
or , if they depart today , brace for strong easterly winds near 31S on
Sunday /Sunday night.

NOTE that if this feature does NOT form, then the waypoint given in the
forecast below will still work OK, but winds near NZ will be westerly rather
than easterly.

===================================================
Here is a voyage forecast for any yachts in Minerva with a cruising speed or
around 6 knots, departing for North Minerva on 1pm Wednesday
(050000UTC) and heading for Opua.

DISCLAIMER: weather is a mix of pattern and chaos. The real world unravels
away from the model output shown here. Computer data does NOT do well near a
coast or in a trough. In a convergence zone computer gives averaged-out
light winds, but occasional squalls can deliver 30 knots for
30 minutes. If your baro strays away from target pressure more than 5 hPa
the forecast needs updating.

DECODE: Time HH:MM is hours and minutes in UTC. Lat and Long are in degrees
and minutes. hPa is barometer in hPa, Wind is compass octant coming FROM and
lull~avg~gust is speed range in knots. Crs-Bsp is boat course to in degrees
TRUE and speed in knots. TWA is the angle between the wind and the boat
course, minus for wind on port. Waves are significant wave height in
metres=average of top third, or are exceeded around once in 7 waves or once
a minute. Add 50% to get the occasional wave which occurs or is exceeded
around once every 10 minutes.

Table is in UTC and degrees True

Head off along 220 True to 29S 176E , to get ready for ESE winds near NZ.
Timestamp | POSITION | Air | WIND | BOAT
|waves
UTC- HH:MM|----Lat:/ Long----:| hPa | lull~avg~gust |Crs-Kt|TWA|Sig~ocnl
05-Nov-00:00|23:37S/178:58W|1017|ENE11~14~21|219-06|-154|2.0~3.0m
05-Nov-04:15|23:57S/179:16W|1016|ENE09~11~17|219-06|-148|2.3~3.4m
05-Nov-08:30|24:18S/179:34W|1018|ENE10~13~19|219-06|-151|2.3~3.4m
05-Nov-12:43|24:38S/179:52W|1017|-NE10~13~19|219-06.1|-164|2.2~3.2m
05-Nov-17:01|24:58S/179:49E|1016|-NE09~11~17|219-05.9|-170|2.1~3.1m
05-Nov-21:24|25:19S/179:31E|1017|-NE09~11~17|220-06.0|-175|2.0~3.0m
gybe
06-Nov-01:56|25:39S/179:12E|1016|NNE06~08~12|220-06|152|1.9-2.8m*
06-Nov-06:47|25:59S/178:54E|1018|NNW02~02~03|220-05|109|1.8-2.7m*
around here we encounter the north end of a passing front- kills the wind,
maybe some drizzle, then new wind from DE, keep going along 220 true
06-Nov-12:05|26:20S/178:35E|1019|SSE05~07~10|220-05|-64|1.7-2.6m**
06-Nov-17:17|26:40S/178:16E|1018|-SE11~14~21|220-05.3|-81|1.7~2.6m
06-Nov-22:01|26:59S/177:57E|1020|-SE14~18~27|220-05.6|-83|1.7~2.6m
07-Nov-02:33|27:20S/177:38E|1019|-SE14~18~27|220-05.6|-81|1.6~2.4m
07-Nov-07:05|27:40S/177:18E|1020|ESE13~16~24|220-05.7|-99|1.5~2.3m
07-Nov-11:38|28:00S/176:59E|1021|ESE12~14~22|221-05.9|-111|1.4~2.2m
07-Nov-16:03|28:20S/176:39E|1020|ESE13~17~25|221-06.2|-116|1.4~2.0m
07-Nov-20:14|28:40S/176:20E|1020|-E-13~17~25|221-06.4|-125|1.4~2.2m
once winds turn E we can go direct
08-Nov-00:22|29:00S/176:00E|1019|-E-12~16~23|194-05.7|-97|1.4~2.0m
08-Nov-06:04|29:31S/175:51E|1019|-E-13~17~25|194-05.9|-101|1.4~2.0m
08-Nov-11:25|30:02S/175:43E|1019|-E-15~18~27|194-06.1|-107|1.4~2.0m
08-Nov-16:33|30:34S/175:34E|1018|-E-14~18~27|194-06.0|-103|1.4~2.0m
08-Nov-21:39|31:05S/175:25E|1019|-E-17~21~32|194-06.1|-102|1.5~2.3m
09-Nov-02:44|31:36S/175:16E|1017|-E-16~20~30|194-06.2|-105|1.6~2.4m
09-Nov-07:54|32:07S/175:06E|1019|-E-16~20~29|194-06.0|-98|1.6~2.4m
09-Nov-13:15|32:38S/174:57E|1018|ESE16~19~29|194-05.8|-87|1.6~2.4m
09-Nov-18:38|33:09S/174:48E|1019|-E-16~20~29|194-05.9|-92|1.6~2.4m
10-Nov-00:18|33:41S/174:38E|1020|ESE14~17~26|194-05.6|-88|1.6~2.4m
10-Nov-06:05|34:12S/174:29E|1019|ESE12~15~23|194-05.5|-90|1.5~2.3m
10-Nov-11:58|34:43S/174:19E|1020|ESE10~12~18|195-05.4|-90|1.4~2.0m
10-Nov-18:08|35:14S/174:09E|1019|ESE08~10~15|ETA off Opua around 8am local
Route distance 807.31nm| route time 5d 18h 08m|||
*= motoring with light winds **= motoring into the wind, or fall off for
comfort but that will take longer.
SWELL : From east until 25S, then from SW until 29S , then from S until
30S, then from SE until 32S then from East/ENE.

Updates from ZKLF Radio fax on 3247.4, 5807, 9459, 13550.5 or 16340.1 kHz Or
HIGH SEAS on ZLM 6224 kHz and 12356 kHz at 0303Z, 0903Z, 1503Z and 2103Z and
on 8297 kHz and 16531 kHz at 0333Z,1003Z,1533Z and 2203Z or, for warnings,
send email to query@saildocs.com, No subject, saying SEND
http://m.metservice.com/warnings/marine
Or SEND http://www.met.gov.fj/aifs_prods/10140.txt
or let me know at bob@metbob.com or TXT/PHN to +6427 776 2212

Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
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02 November 2014

Bob Blog

WEATHERGRAM
YOTREPS
Issued 02 November 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world TROPICAL TOPICS Tropical cyclone activity at present
includes VANCE off the west Mexican Coast and NURI off the east of Japan.
Weekly rain maps show that the main rain has been associated with tropical
cyclones. In the South Pacific the convergence zone seems to have cleared
last week over northern Vanuatu and intensified from northern Fiji to Samoa.
Otherwise not much change.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is steady in position and fluctuating in intensity and expected to be
weaker this week than last week. Many over the sea between Solomons and
northern Vanuatu, with another branch from northern Fiji to Samoa extending
SE towards French Polynesia.
Part of the energy from the SPCZ is expected to help deepen a low in the
mid- latitudes near 35S 150W (South of French Polynesia) by Wednesday.

STR= Sub-tropical Ridge
The STR has been strong during October.

High between Tonga and NZ today is expected to stall near 30 to 40S 160W
from Tuesday to Thursday and then fade  should maintain steady ESE winds in
the tropics on its northern sidemay be somewhat enhance along 12 to 18S
from 165 to W to 180.
Second HIGH crossing Tasmania on Monday is travel NE onto northern NZ by
Friday and then travel east away from northern NZ early next week.

Between the tropics and NZ
Vessels in the All Points Rally (www.islandcruising.co.nz/?page_id=1687)
are mostly underway now with a good weather pattern for sailing to Opua, NZ
from Tonga, Fiji, or Vanuatu. This rally is free of charge (thanks to the
sponsors) and helps participants with planning, weather info, clearance, and
seminars on how to enjoy NZ.

The first factor to consider a departure date is the local weather: the
SPCZ does have some convective cloud over northern parts of Fiji at present
but is not very intense and isn't really strong enough to delay departure
this week.

The second restraint on a weather window is to pick an ETA over northern
NZ that does NOT have strong adverse winds. Northern NZ is expected to
have a period of light winds early next week as the second High mentioned
above passes bylooks good -- until Wed 11 Nov when the next front and SW
winds arrive.

The third factor is to avoid gales and heavy swells during the trip.
Good news is there isn't much to report this week. The replacement trough
between the Highs is crossing the North Island on Monday and may form a
little secondary low east of the North Island on Wednesday/Thursday, but
this doesn't affect Northland. There is a possibility that a week tropical
trough may cross the region between Fiji and NZ on Sunday 09 /Monday 10 Nov
 that could form some showers and enhance the easterly winds just north of
NZ and so shouldn't be a hassle and may be a help.

Minerva is likely to have winds between ENE and ESE 10 and 20 knots this
week with swell from E then S then SE around 2 metres.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe:
click the "unsubscribe" link on the bottom of the email from WordPress, or,
if email wasnt from WordPress then send a reply email saying LEAVE.

26 October 2014

Bob Blog issued 26 Oct

WEATHERGRAM
YOTREPS
Issued 26 October 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world Coming Cyclone Season

NIWA has issued a Tropical Cyclone outlook for the coming South Pacific
cyclone season.
For the details go to (www.scoop.co.nz/stories/SC1410/S00048/southwest-
pacific-tropical-cyclone-outlook.htm
)
In summary NIWA expect the coming season to bring a near average number of
cyclones (8 to 12 in all), with the normal slow start, and February/March
peak.
VANUATU and NEW CALEDONIA are expected to have lower than normal risk.
A zone of slightly higher than normal risk is expected to stretch from
TUVALU across TOKELAU/SAMOA, to between NIUE and SOUTHERN COOKS. These are
expected to be only small variations from normal and so vigilance is
recommended.

Madden Julian Oscillation MJO
During the warmer months of the year we can anticipate phases of extra
convection in the South Pacific by watching the MJO. This index is NOT
having much impact on tropical convection during the coming week. My future
blogs will give more info about it.

TROPICAL TOPICS
Tropical cyclone activity at present includes ANA which has maintained its
integrity since re-curving wets of Hawaii early last week and is now
unravelling but its components may well reach the Victoria coast of CANADA
this week. There is also a feature currently name 04A FOUR in the Arabian
Sea.

Weekly rain maps show that there was heavier rain in the past week over
Solomons/ northern Coral Sea than in the previous week.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ strengthened in the past week but is expected to weaken and become more
spread out this week, mostly drifting north.

STR= Sub-tropical Ridge
High between Fiji and NZ today is expected to travel steadily eastwards
along 25 to 30S to 150W by Thursday and then to the southeast.
Another HIGH is expected to move form Aussie bight into Tasman Sea on
Wed/Thu and then eastwards along 30S on Fri/sat/sun. This makes for a
strong STR all week.
Another HIGH is in the south Tasman Sea tonight and expected to fade as it
crosses southern/central NZ on Monday. This high is just a break between
the troughs in the Southern Ocean and for the rest of the week the strong
disturbed westerly winds that are typical of spring dominate the Tasman
Sea/NZ pattern.
The ECMWF model (tinyurl.com/ecaus) shows that the STR is likely to spread
southwards on to NZ early next week (4 Nov).

Between the tropics and NZ :
Vessels in the All Points Rally (www.islandcruising.co.nz/?page_id=1687)
are looking for a good weather pattern for sailing to Opua, NZ from Tonga,
Fiji, or Vanuatu. This rally is free of charge (thanks to the sponsors) and
helps participants with planning, weather info, clearance, and seminars on
how to enjoy NZ. I shall do my bit here by commenting on windows of
weather to get to NZ.
The first factor to consider a departure date is the local weather: the
SPCZ does have some convective cloud over northern Vanuatu and parts of Fiji
at present but is not very intense and seems to be likely to drift north and
spread out. It isn't really strong enough to delay departure this week.
The second restraint on a weather window is to pick an ETA over northern
NZ that does NOT have strong adverse winds. Northern NZ is expected to
have strong winds from Monday to Thursday. Then these winds should ease
over the weekend 1-2 Nov and be light and variable early next week 3-4 Nov.
Arranging your trip to reach NZ on 3-4 and maybe 5 Nov looks OK at this
stage. Beyond that is too far away to tell at this stage.

The third factor is to avoid gales and heavy swells during the trip.
Sadly a burst of 3 to 4 metre swell from the southern Ocean moving as far
north as 23S by Friday in area north of NZ. This is in the STR and winds
will be light: no whitecaps, and the swells will have long periods of 11 to
12 seconds, so it is likely to be a gentle encounter. However it may
require a watchful hand on the tiller, and may be uncomfortable.
Anyone wish in avoid sailing in these condition should delay getting to 23S
until after Friday.
Those who intend to go to North Minerva and wait there for a good sailing
window are likely to have an OK wait until Thursday this week , then those 3
metre swells are expected to briefly reach the area (outside the
reef) on local Friday night (in time for Halloween) easing again on
Saturday.
MINERVA REEF
UTC | hPa |Dir kt| m | %
27-Oct-14 0000|1017|088|13|2.1|19
27-Oct-14 0300|1017|093|13|2.0|12
27-Oct-14 0600|1016|092|14|2.0|5
27-Oct-14 0900|1017|087|15|1.9|4
27-Oct-14 1200|1017|085|14|1.9|3
27-Oct-14 1500|1017|087|13|1.8|2
27-Oct-14 1800|1018|092|13|1.7|1
28-Oct-14 0000|1018|098|14|1.6|0
28-Oct-14 0600|1018|108|15|1.6|1
28-Oct-14 1200|1018|102|15|1.6|1
28-Oct-14 1800|1017|104|15|1.5|0
29-Oct-14 0000|1017|093|13|1.5|0
29-Oct-14 0600|1016|087|14|1.4|1
29-Oct-14 1200|1017|056|11|1.4|2
29-Oct-14 1800|1016|036|06|1.3|3
30-Oct-14 0000|1015|092|01|1.3|2
30-Oct-14 0600|1016|150|06|1.2|1
30-Oct-14 1200|1016|118|05|1.2|0
30-Oct-14 1800|1017|124|06|1.3|28
31-Oct-14 0000|1017|132|08|1.6|56
31-Oct-14 0600|1017|130|11|2.5|73
31-Oct-14 1200|1018|103|10|3.0|89
31-Oct-14 1800|1018|114|10|3.0|83
01-Nov-14 0000|1019|121|11|2.8|77
01-Nov-14 0600|1019|119|16|2.5|79
01-Nov-14 1200|1020|107|15|2.4|80
01-Nov-14 1800|1020|114|15|2.2|83
02-Nov-14 0000|1020|114|16|2.3|87
Spot read out at Minerva; hPa is air pressure, Dir kt is wind
direction true and speed in knots, m is wave height in significant metres,
% is cloud cover SO the decision about when to depart depends on these three
factors as well as speed of vessel and crew expectations, and the answer
will be
different for different vessels. Normally at this time of the year
there can be paralysis by over-analysis, especially at the Minerva yacht
club.
The good news is that there are NO gales expected to south of 30S after
Thursday- just that period of enlightened swells to factor in. Next week
could well be different.


See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe,
send a reply email saying LEAVE.

19 October 2014

Bob Blog issued 19 Oct 2014

WEATHERGRAM
YOTREPS
Issued 19 October 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and was near to -10 (Australian units)
during September but is now less extreme indicating that the recent trend
towards an El Nino is relaxing.

TROPICAL TOPICS
Tropical cyclone activity at present includes GONZOLA (after its direct hit
with Bermuda) heading for Scotland, and ANA going north to west of Hawaii.
The remains of HUDHUD over India last week caused a storm that brought
unseasonal blizzards to the Himalayas killing more than twenty trampers.

WEATHER ZONES

SPCZ=South Pacific Convergence zone.
SPCZ is expected to strengthen this week and to slowly spread south onto
Fiji from Tuesday, and possibly onto northern Vanuatu and Tonga on Sat/sun
25/26 Oct.
The week starts with a frontal zone attached to a deep low near 30S 155W
(low traveling south), and the north end of this is expected to move east
across French Polynesia FP, turning into a convergence zone over southern FP
by the end of the week.

STR= Sub-tropical Ridge
High over Tasmania on Monday is expected to travel NE across the Tasman Sea
and fade near Norfolk by Friday. Another HIGH is expected to travel south
of 45S past south of Tasmania on Thursday and then travel NE across central
or northern NZ on Sat/Sun 25/26, followed by a trough over northern NZ on
Monday and then a SW flow on Tuesday.

Between the tropics and NZ
Vessels in the All Points Rally are busy preparing for their trip to NZ from
Tonga, Fiji, or Vanuatu, to Opua. This rally (http://www.
islandcruising.co.nz/?page_id=1687) is free of charge (thanks to the
sponsors) and helps participants with planning, weather info, clearance, and
seminars on how to enjoy NZ. I shall do my bit here by commenting on
windows of weather to get to NZ.
The first factor to consider a departure date is the local weather: the
SPCZ is expected to travel south on Fiji from Tuesday and then onto northern
Vanuatu and Tonga around 25/26. Better to depart when the SPCZ is NOT
around.
The second restraint on a weather window is to pick an ETA over northern
NZ that does NOT have strong adverse winds. The table below is a spot
read out for Cape Reinga over northern NZ and things looks good this coming
week except for a passing front on local Tuesday morning around 20
1800UTC. Note that the next front is expected on Mon 27 Oct followed by
SW winds on 28th, so try and reach 30S on 28 Oct and that way you should
avoid the most adverse parts of that front.
CAPE REINGA
UTC |hPa |dir kt | m| %
20-Oct-14 0000|1019|234|13|2.2|0
20-Oct-14 0300|1019|222|14|2.2|1
20-Oct-14 0600|1018|215|18|2.2|2
20-Oct-14 0900|1018|230|15|2.2|3
20-Oct-14 1200|1019|247|16|2.1|5
20-Oct-14 1500|1019|247|19|2.1|39
20-Oct-14 1800|1019|206|22|2.3|74
21-Oct-14 0000|1021|198|20|2.6|54
21-Oct-14 0600|1021|185|21|3.0|21
21-Oct-14 1200|1023|162|15|3.1|21
21-Oct-14 1800|1022|147|13|3.0|23
22-Oct-14 0000|1023|145|08|2.9|23
22-Oct-14 0600|1022|147|06|2.8|7
22-Oct-14 1200|1023|117|03|2.8|2
22-Oct-14 1800|1022|100|03|2.8|47
23-Oct-14 0000|1021|073|02|2.7|76
23-Oct-14 0600|1020|227|03|2.5|68
23-Oct-14 1200|1019|248|06|2.4|60
23-Oct-14 1800|1019|226|11|2.3|53
24-Oct-14 0000|1019|216|13|2.1|45
24-Oct-14 0600|1019|208|12|2.0|70
24-Oct-14 1200|1020|201|09|2.0|94
24-Oct-14 1800|1020|233|10|1.9|78
25-Oct-14 0000|1020|222|10|2.0|61
25-Oct-14 0600|1021|195|10|2.1|31
25-Oct-14 1200|1022|171|09|2.1|1
25-Oct-14 1800|1022|160|05|2.1|1
26-Oct-14 0000|1022|182|05|2.0|2
Spot read out at Cape Reinga; hPa is air pressure, Dir kt is wind
direction true and speed in knots, m is wave height in significant metres,
% is cloud cover The next timing constraint is the middle part. This week
(for sail boats) it is to try and avoid the light variable winds that belong
to the centre of passing Highs in the STR. This is difficult when the STR
is strong and placed across the middle of the route. May be better to wait a
week or two for more wind.
Those who intend to go to North Minerva and wait there for a good sailing
window are likely to have an OK wait this coming week-nothing uncomfortable
is expected at Minerva:
MINERVA REEF
UTC | hPa |Dir kt| m | %
20-Oct-14 0000|1016|089|04|2.5|85
20-Oct-14 0300|1016|117|03|2.5|87
20-Oct-14 0600|1015|144|02|2.5|89
20-Oct-14 0900|1015|163|03|2.4|65
20-Oct-14 1200|1016|170|03|2.4|41
20-Oct-14 1500|1016|180|04|2.4|36
20-Oct-14 1800|1016|164|06|2.3|31
21-Oct-14 0000|1016|140|06|2.2|52
21-Oct-14 0600|1016|139|09|2.1|7
21-Oct-14 1200|1016|137|09|2.0|43
21-Oct-14 1800|1016|139|10|1.9|83
22-Oct-14 0000|1016|133|12|1.9|99
22-Oct-14 0600|1016|133|14|1.8|97
22-Oct-14 1200|1017|123|12|1.8|63
22-Oct-14 1800|1017|126|13|1.7|25
23-Oct-14 0000|1016|103|11|1.8|32
23-Oct-14 0600|1016|102|12|1.9|46
23-Oct-14 1200|1016|084|10|2.0|60
23-Oct-14 1800|1015|096|08|2.0|73
24-Oct-14 0000|1015|114|09|2.0|85
24-Oct-14 0600|1015|113|12|1.9|61
24-Oct-14 1200|1015|109|10|1.9|36
24-Oct-14 1800|1015|121|11|1.8|66
25-Oct-14 0000|1015|124|13|1.7|96
25-Oct-14 0600|1015|120|16|1.7|98
25-Oct-14 1200|1015|113|15|1.7|99
25-Oct-14 1800|1016|118|16|1.8|92
26-Oct-14 0000|1016|123|16|1.8|84
Spot read out at Minerva; hPa is air pressure, Dir kt is wind direction
true and speed in knots, m is wave height in significant metres, % is cloud
cover The front that is expected to be crossing northern NZ on Tuesday is
likely to continue NE and peel off to the east across the Kermadecs on
Wednesday If already at Minerva then may as well wait until after this
front (as it is followed by southerly winds and swell) so wait until late
Wednesday or Thursday before proceeding from Minerva to NZ.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe,
send a reply email saying LEAVE.

12 October 2014

BOB Blog issued 12 Oct 2014

WEATHERGRAM
YOTREPS
Issued 12 October 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

The latest NIWA monthly update for a seasonal outlook for the South Pacific
is going for a continuation of drier than normal conditions over most of the
South Pacific area during the next three months.

Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and was near to -10 (Australian units)
during September but is now less extreme indicating that the recent trend
towards an El Nino is now relaxing.

TROPICAL TOPICS
Tropical cyclone activity at present includes Very Severe Cyclone HUDHUD
which has just made landfall over eastern India, VONGFONG which is visiting
Japan, and FAY, a storm in the North Atlantic.
The weekly rain maps show that the heaviest rain is associated with the
tropical cyclones. There has also been some intense rain in the eastern
Coral Sea for the past two weeks.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to weaken this week and be loosely lying from south of
Solomons Islands to between Samoa and Fiji. A few showers associated with a
fading trough are likely over Vanuatu until Monday.

STR= Sub-tropical Ridge
High over northern NZ has managed to arrange just light winds above it and
so is a slow-moving feature and should fade just NE of NZ on Wednesday.
Another HIGH is expected to form over southern NZ on Tuesday and then to
move NE towards 35S 160W, to east of NZ, by end of the week. There is
expected to be a zone of enhanced easterly winds in the tropics and on the
north side of this HIGH-a squash zone.

Departing westwards from Tahiti:
There may be a branch of the SPCZ to avoid over the area especially after
Wednesday.
The squash zone is likely to be mainly south of 25S so should not be too
much of a bother.

Between the tropics and NZ
The vessels associated in the All Points Rally will now be involve in
preparations for their voyage, be it from Tonga, Fiji, or Vanuatu , to
OPUA. The Rally is free of charge (thanks to the sponsors) and helps
participants with planning, weather info, clearance, and seminars on how to
enjoy NZ. See more at www.islandcruising.co.nz/?page_id=1687
and register at www.islandcruising.co.nz/?page_id=1268.
I shall be commenting on windows of weather to get to NZ for these people
here for the next few weeks.
There is a good window for getting to NZ from New Caledonia/Vila/NZ, until
Tuesday anyway. However there is a Low lingering between Tonga and NZ on
Monday/Tuesday so not comfortable to get to NZ from Tonga. As the High that
is forecast to be over NZ this week starts moving off to the east there
should be a northerly flow between it and the next Low that should then be
approaching from the Tasman Sea. This northerly flow can be useful, but the
low itself is no good at all for your voyage. At
present the low or trough is expected to reach NZ on Sun 19/Mon 20 Oct
followed by a brief period of SW winds, then NE winds ahead of a new low.
You can maybe weave between these winds with good timing if you are lucky,
or wait for a better looking pattern.
My choice of weather model for planning purposes is tinyurl.com/ecaus

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com
To unsubscribe, send a reply email saying LEAVE.

05 October 2014

BobBlog

WEATHERGRAM
YOTREPS
Issued 5 October 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

8 October eclipse
Many of you will be watching the full moon rise with the setting sun on
Wednesday evening. And there is a lunar eclipse this month as well, so that
a few hours after moon rise you can watch it get shaded by earths shadow.
Eclipse starts at 0817UTC and finishes at 1332UTC, should be compelling
viewing if local clouds keep away .
This eclipse reminds me that when the full tide is in the middle of the
night after the October full moon (and thats around 15 Oct this year) there
may be a spawning of the Palolo coral warm. They drop off their worm-tails
or pods; jade (female) or brown (male), and these mix together in the
swirling tide, with each having a light sensitive spot that directs it
towards the moon (then sinking in the west) or a flashlight.
At dawn the pods dissolve, allowing eggs and sperm to get together and form
the new generation. The rising is only on the turn of that one tide and only
takes place for a few hours. Actual timing varies each year, and may be in
November rather than October.

This is worm-sex, Pacific style. The pods can accumulate in the sea in
massive amounts. Ask the locals about this and if you time it right you may
be about to collect some of this rare delicacy, or photo it. They might look
yucky, but taste really nice on toast, something like caviar, so Im told.

Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September, but is slightly relaxing so far in October.
The amount of heat that is being stored in the sea in the Eastern Equatorial
Pacific has also increased, as measured by the NINO3.4index.
The atmosphere and ocean are in cahoots.

TROPICAL TOPICS
At this time of the year, with the sun directly overhead the 5 to 10S zone ,
we need to be mindful of a phenomenon called Cyclone twinning whereby a
cyclone forming near 5 to 10N in the northern hemisphere seems to influence
the formation a feature of similar size and shape in the southern
hemisphere. This happens reasonably often in the Indian Ocean (see
http://lnk.ie/U9SS/e=bobmcdavitt@hotmail.com/http://www.wunderground.
com/blog/JeffMasters/article.html?entrynum=2402
) and was maybe a factor in
the formation of the infamous cyclone Bebe in the South Pacific in 1972.
There is possibly some twinning occurring with features around 10N and
10S at presentbut no cyclone twinning. Westerly winds near the
equator can be part and parcel of low pressure systems at both 10N and 10S.
And a streamline analysis (from MetService) shows equatorial S/SW winds to
north of Papua New Guinea.
As for Tropical cyclone activity at present we have TC PHANFONE and VONGFONG
in the NW Pacific, and SIMON off the Mexican west coast.
The weekly rain maps show the heaviest rain around 140E and part of it over
western Solomon Islands.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to be active in the zone from Solomon Island across the
Coral Sea to New Caledonia between now and Tuesday, extending across Loyalty
Islands to south of western Fiji on Wednesday and Thursday, easing away on
Friday. There is also a weak convergence zone from northern Tonga to
Southern Cooks and an active trough that is expected to lurk around 140W to
south of 20S from Tuesday until Friday

STR= Sub-tropical Ridge
The High travelling east along 30S from Australia is expected to bring a
brief period of light winds to NZ on Tuesday. The next high is expected to
be in the Australian bight on Wednesday a more summer-like latitude.
This high is expected to travel east along 30/35 across the Tasman Sea on
Thursday/Friday and northern NZ on Sat/Sunday. This provides a very good
weather pattern for anyone wishing to sail southward towards NZ.

Departing westwards from Tahiti:
With just that weak convergence zone to contend with the weather pattern is
looking reasonable for westward travel. Note that towards the end of the
week, a high cell is expected to travel east along 30S - and there is likely
to be a zone of enhanced SE trade winds on its northern side, especially
along 20S.

Between the tropics and NZ
With the prospect of a high crossing northern New Zealand next weekend, this
implies and good weather pattern for setting sail to NZ over next few days.
However a departure from Tonga /Fiji/ on Monday to Wednesday or from Noumea
on Monday/Tuesday, is likely to start off with strong SE winds.
SO it is a mixed week.
Note that fronts with squall winds are expected to affect North Island on
Monday and Wednesday.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe,
send a reply email saying LEAVE.

28 September 2014

BobBlog 28 Sep 2014

WEATHERGRAM
YOTREPS
Issued 28 September 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.
Barometer jumps
A yacht skipper at anchor in a river on the NE end of Baie de Prony (at SE
end of New Caledonia) last Wednesday morning noticed
his barometer jump up 3 hPa in an hour and then down in the next hour, and
once again.
These jumps were superimposed upon the normal semi-diurnal atmospheric tide
that the barometer was recording as a series of bumps
that look like Sine waves. The STRANGE thing is that nothing happened to
the wind or cloud in the area (usually a change of this
magnitude is associated with an incoming gale or a nearby squall). Nothing.

Later he found out that another boat anchored 10 miles further south
observed much the same thing.
Does anyone have an explanation of such an observation??

Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one
number. It is based on the standardised difference in the barometer
readings between Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) for
much of September.
The amount of heat that is being stored in the sea in the Eastern Equatorial
pacific has also increased during September, as measured by the
NINO3.4index.
During an El Nino episode, weather patterns tend to be drawn closer to the
equator. The subtropical ridge in the southern hemisphere tends to be north
of its normal position and this weakens the trade winds.
The South Pacific Convergence zone tends to be tugged north and east of its
normal position. If this happens during the cyclone season then it increase
the risk of cyclone formation about and east of the dateline, especially
during February and March.
In itself an El Nino episode doesn't have much impact on cyclone activity
about New Caledonia, but it may reduce the risk in the Coral Sea.

Sea surface temperatures are currently warmer than normal in a zone from
Samoa to French Polynesia
so this is likely to be a zone of extra convection when visited by the SPCZ
in the next few weeks.

TROPICAL TOPICS
In the East Pacific we have RACHAL and in the west Pacific we have KAMMURI
The weekly rain maps show a shift of the heaviest rain from 100E to 140E.


WEATHER ZONES
SPCZ= South Pacific Convergence Zone
The SPCZ is more homogeneous and more intense this week than it was last
week and is averaging its position across Solomons to Tuvalu, but there has
also been convection over Vanuatu last week. SPCZ is expected to shift
southwards of Solomons towards Vanuatu on 4/5 Oct. The convergence
zone/trough which is crossing Vanuatu tonight is expected to weaken over
Fiji on Monday and fade over Tonga on local Tuesday.

STR= Sub-tropical Ridge
The STR is now mainly along 25S across the South Pacific, perhaps somewhat
north of its normal position, and certainly allowing the roaring 40s to roar
over the mid-latitudes.

Departing westwards from Tahiti:
There may be some scattered convection about Suwarrow this week, nothing
organised. Otherwise all is looking good for sailing west from Tahiti to
Tonga this week.

Between NZ to the tropics
A jetstream is triggering a rapidly developing low to NE of North Island
tonight and this low is expected to travel SSE over the next few days,
sideswiping eastern North Island. Not good for approaching NZ but maybe Ok
for getting north. This development wriggles the upper air so that another
jetstream forms an even deeper low near 130W by Wednesday, It is when a
jetstream is switched from zonal to meridonal that we get these surface lows
developing.
The next trough in the Tasman Sea is expected to cross northern NZ on
Thursday, followed by strong SW winds and big SW swells in the north Tasman
Sea on Fri. Avoid.
There may be some big SW swells left over in the Tasman Sea around Norfolk
Island on Saturday. Then the next High from Australia should bring in
settled conditions on Sunday/Monday/Tuesday, so try and time your trip
accordingly.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe,
send a reply email saying unsubscribe.

21 September 2014

BobBlog issued 21 Sept

WEATHERGRAM
YOTREPS
Issued 21 September 2014

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world

1. Resolution
The global computer models take weather observations and transfer them onto
a grid of dots, thereby averaging the weather out. Features that are
occurring between the reports of the observation network are missed
altogether, but some data such as temperature is observed in a continuous
fashion by remote sensing from satellites and is covered well. The model has
to balance this matrix of dots to ensure that certain rules are observed,
for example all the computed upward motions need to be balanced by down ward
motions so that the total atmosphere remains intact. Once a captured and
balanced pattern is obtained, it is then pushed into the future using
dynamic equations in small time-steps. Then another balancing computation is
done and so forth. SO the GRIB data of a weather forecast is just a
mathematical idea based on the extrapolation of a captured pattern. In the
real world chaos is continuously jiggling the weather pattern in to a
different direction, so that the weather forecast deviates from the real
world.

You may already be aware of the limitations of GRIB data. Sometimes someone
will offer you GRIB data with a better resolution, and the question arises
if it will have better accuracy. The answer is somewhat mixed, as I hope to
show you today:

If you can, check my Weathergram graphical edition on the web at/metbob.
wordpress.com to see the comparison of a map showing normal GRIB data from
the GFS model with another from the 8km resolution Predictwind version of
the GFS model (PWG) as available (under registration) from
http://lnk.ie/TPYD/e=bobmcdavitt@hotmail.com/http://www.predictwind.com

The PWG model captures some terrain effectslowering the air pressure in the
interior of the main islands of Fiji in the heat of the day, and there by
forming a westerly sea-breeze around Nadi/Lautoka and causing an
acceleration of the wind on the SW end of Fiji near Navula Passage. All of
these terrain effects truly happen, even if they are not resolved by the
normal GRIB data.

These models with higher resolution and closer dots (and smaller time-
steps) require heaps more computing than the normal global models and give a
pattern that is somewhat closer to the real world. However there is no
increase in the basic weather observation resolution that goes into these
models, so they still have limitations. Their output is still just an
averaged idea.

2 Equinox

Welcome to the vernal equinox today. That was when the overhead sun shifted
from the northern hemisphere to the southern hemisphere. It is only on the
equinox that the sun rises due east and sets due west.
Astronomers, logically, time the seasons using the solstices and equinoxes
of earths orbit around the sun. By this reckoning, spring starts with
vernal equinox. Note that this makes our winter last 93 days and summer 89
days because the earths orbit is slightly elliptical and the earth speeds
up a bit during our summer.
For practical purposes climatologists measure climate data averaged over
each calendar month, and by this reckoning the months of September to
November are taken as spring. Note that by this reckoning summer lasts
90 days (91 days in a leap year). In New Zealand this method of marking the
seasons is more popular than using the equinox and solstice. Fair enough, it
adds 1 or 2 days to summer J You may have noted that the time between
sunrise and sunset is NOT 12 hours today, but around 7 minutes LONGER. This
is because sunrise is defined at the time the top limb of the sun is just
visible on the horizon, and similarly sunset is defined with the top limb of
the sun disappears below the horizon. Due to refraction of the atmosphere
the sun appears and disappears when is slightly below the horizon. This
explains the extra day light. The name used to describe the date when time
between sunrise and sunset crosses twelve hours is the equilux as described
at wikipedia.org/wiki/Equinox Over the next few weeks, as we get to notice
the longer days there will be extra warmth reaching the southern ocean. Sun
starts to shine reach Antarctica after six dark months. Just as the coldest
part of night for us is just after dawn, so it is that Antarctica gets is
coldest temperatures of the year around the equinox. It is the temperature
difference across the Southern Ocean that energies the westerly winds found
there, and so these at their most energetic, and expand to their furthest
north, around the equinox. This is the origin of the term equinoctial
gales, however I prefer the phrase gales of the Antarctic dawn.
Note that New Zealand will be putting their clock forward an hour next
Sunday (28 Sep) and changing to NZDT. New South Wales changes on 5 October.

Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin. It has been negative since July and dived below -10
(Australian units) at the start of September where it has hovered ever
since.  if it holds below -10 for another few weeks then we can call this a
full-blown El Nino.

TROPICAL TOPICS
In the east pacific we have POLO and in the west Pacific we have FUNG- WONG.
The weekly rain maps show a shift of the heaviest rain from India/Pakistan
to the Taiwan area with TC FUNG-WONG.

WEATHER ZONES
SPCZ= South Pacific Convergence Zone
The SPCZ is fragmenting into several branches this week, and slowly
intensifying. One branch is expected to form in the northern Coral Sea
between Monday and Thursday, with a squash zone of enhanced SE winds on the
south side of this zoneavoid.
One of these convergence zones is expected to affect Fiji on
Friday/Saturday, and another to affect Vanuatu/ Loyalty Group on Sunday.

STR= Sub-tropical Ridge
The STR is at its normal latitude for this time of the year, along 20 to 30S
The HIGH over eastern Australia is expected travel across the Tasman Sea
from Tuesday to Thursday and northern NZ on Friday followed by a trough on
Saturday night and disturbed SW over NZ by Sunday.

Departing westwards from Tahiti:
A trough is travelling west along 20S followed by southerly winds and big
SW swells. It is expected to reach Niue by local Sunday, southern cooks by
local Monday/Tuesday, and fade over Australs by local Wednesday.
It is expected to be followed by a period of trade winds that look good for
going west , but might be a squash zone forming along 10 to 15S this weekend


Between NZ to the tropics
Vigorous SW/S flow over NZ on Monday as a Low from the southern ocean
sideswipes its eastern coasts. Then settled weather until the next trough
approaches with NW winds on Friday night/Saturday, then the trough itself on
Saturday night, and then a SW flow on Sunday 28th.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com  Feedback to bob@metbob.com To unsubscribe,
send a reply email saying unsubscribe.

14 September 2014

BobBlog issued 14 September

WEATHERGRAM
YOTREPS

Issued 14 September 2014
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

1) One of my yachts encountered the South Pacific convergence zone that was
lurking to north of Fiji last Wednesday night/Thursday. He reported
(Abridged):
>>>>>>>>>>>>>>>>>>>>
I'm currently at 15 06S, 179 41E, on passage from Samoa to Port Vila,
Vanuatu. We left Savai'i Island on Sunday 7th Sep after hanging around for a
bit waiting for a window where the winds weren't going to be too strong.
After a day or so of 10 - 15 knot winds, they began to build from the SE
quite significantly.
2 days ago at around 7am, end of night watch, we were at 14 12S, 176 00W,
and with a GFS GRIB forecast of 12 knots we had winds around 21 knots. It
continued to build steadily from there, yesterday at 7am we were at 14 48S,
179 06W with winds around 28 knots (forecast 13), and at the moment we have
winds touching the bottom of the gale force range at a steady 36 knots
(forecast for here and now is 15 knots) with gusts to 44 or so. I'm looking
at the GFS file that I picked up a few hours ago, and I can see that just
ahead, about where we will be at 1pm today, there are forecasts around 22
knots. If I was a betting man then I would be putting my money on the actual
winds being steady in the 50+ knots range with perhaps peaks touching 60
knots.
I'm running at the moment with essentially a tri sail and storm jib and
although it's tempting to douse the tri sail there is also a swell that's
been building from 4 metres and the tri sail is helping to reduce the roll a
bit. I have suffered a bit of minor rigging and structure damage out at the
aft deck but nothing too serious.
I guess that my main concern is that in amongst all of this there is nothing
from the various weather bureaus warning of this. I think that if any sailor
is venturing out into waters where the wind is blowing 50 knots or more,
especially where we are which is in reasonably well trafficked waters just
north of Fiji, they would expect at least a gale warning if not a storm
warning. There are no warnings at all from Fiji Met Service and none from NZ
MetService for this area, despite the actual winds having been blowing in
the "strong wind warning" range for over 24 hours now, and we're now in the
range where I would expect a gale warning to be issued, right now, for the
area we are in.
I also have no real idea if the anomaly between forecast wind and actual
wind (about 100% difference or a bit over as of the last 36 hours) is due to
some kind of local conditions.
So, a few things.
Can we get a gale warning issued for these waters at the first available
opportunity please? As a gale warning would be expected for any area where
gale force winds are likely to happen, and as there are gale force winds
blowing right here and now I think it's fair to warn other boats.
Are these conditions likely to continue? We're going to try to hold a course
close to 245M / 257T to get us to Port Vila, Vanuatu. I'm now treating the
GFS GRIB data as a work of fiction, but if you weather boffins can give me
some idea whether these winds are likely to build up to and past 50 knots
that would be appreciated.
Are these conditions entirely local or is there somewhere we can go that's
likely to give us a bit of relief, if not from the winds then at least from
the swell which is continuing to build (with a lot of white caps and a
significant amount of foamy spray as well)? With the amount of swell we have
at the moment, not to mention waves breaking over the base of the mast and
as high as the lower part of the HF antenna, it's a wonder I can hear
anything and unsurprising that I can't be heard.
>>>>>>>>>>>>>>>>>>>
He was caught in some squalls on the south end of the South Pacific
Convergence zone and you can sense his frustration with these gale-like
winds and increasing swell. In this case the way out of the SPCZ was to go
south, and I was able to check the WINDSAT satellite and the animated
satellite imagery from to show him (when he finally got good Internet at
Vila) that this was indeed isolated squall activity and thus unlikely to be
given a gale warning on a high seas forecast, even though the local winds
were gale-force.

Let this be a warning to us  there are limitations to weather forecasts:
the weather computers that produce those GRIB files just average the
weather out, and DO NOT resolve the details in the South pacific Convergence
zone, also the High Sea forecasts do NOT issue gale warning for squalls
that come and go along the SPCZ.
>>>>>>
2) There is a rare double solar flare passing by our planet at present, with
stunning aurora and also some possible disruption to satellite
communications.
>>>>>
3) For readers with internet access: If you enjoyed last weeks experiment,
here is another go from some college students:
https://www.youtube.com/watch?v=JsoE4F2Pb20,
and another showing how to get an hard-boiled egg into and out of a bottle
https://www.youtube.com/watch?v=28TIyWdfxxc
>>>>>
Background influences
The Atmosphere: The Southern Oscillation Index SOI (30 day running mean)
sums up the weather pattern over the South Pacific as one number. It is
based on the standardised difference in the barometer readings between
Tahiti and Darwin.
It has been negative since July and dived below -10 (Australian units) a
week ago, and relaxed a little in the past week  if it holds below -10 for
a month then we can call this a full-blown El Nino.

TROPICAL TOPICS
In the ATLANTIC we have EDOUARD, off the Mexican coast there is ODILE and a
tropical depression, and in the Pacific NW we have KALMAEGI.
The weekly rain maps show that a rain burst has been hovering around
northern India for the past fortnight. Indeed, Kashmir seems to be the worst
affected area, with an estimated 200 deaths in India and another
200 in Pakistan.

WEATHER ZONES
SPCZ= South Pacific Convergence Zone
The SPCZ is slightly weaker than last week, and by Wednesday is expected to
be hugging the 10S line from PNG to east of Samoa. It may shift a little
further south later in the week.

STR= Sub-tropical Ridge
The STR has reverted to its normal latitude for this time of the year and
this pattern may last for a week or two, with no sign now of the blocking
that was affecting the pattern over the past month or so. This week the High
cells with the STR are expected to travel east along 30S.

Departing westwards from Tahiti:
A convergence zone is expected to slide east across the southern parts of
French Polynesia during local Monday and Tuesday, followed by a period of
easterly winds. These easterly winds should be well maintained by a high
cell traveling along 30S, and should be good for going west.
The SPCZ may affect Suwarrow from time to time. Also there may be a small
squash zone of SE winds near 16S late in the week. And the north end of a
trough is likely to cross Southern Cooks late in the week. Otherwise it is
looking to be an OK week for sailing westwards good for travelling west.

Between NZ to the tropics
A trough is expected to be crossing Northland on Tuesday, followed by
another on Thursday night/Friday/Saturday. Avoid.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram text only (and translator) is at weathergram.blogspot.co.nz
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe.
My website is at metbob.com Feedback to bob@metbob.com To unsubscribe, send
a reply email saying unsubscribe.

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