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

27 November 2016

Bob Blog 27 Nov

WEATHERGRAM
YOTREPS
Compiled 27 November 2016
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 Tropics
A tropical low formed in Coral Sea last week and faded as it travelled southward
to west of New Caledonia.
We start this week with another tropical low in the Coral Sea, and this one is
likely to fade somewhere near New Caledonia mid-week. It has been picked up in
the tropical tidbits web site and here is its likely track according to some
weather models, as seen at
www.tropicaltidbits.com/storminfo/96P_tracks_latest.png

Fiji Met service is watching another tropical low tonight located near
Rarotonga.
Their latest idea on its future can be downloaded from
www.met.gov.fj/aifs_prods/20036.txt
>>>>>>>>>>>>>>>
Tropical Disturbance Summary For area Equator to 25S, 160E to 120W
ISSUED FROM RSMC NADI Nov 270833 UTC.

TROPICAL DISTURBANCE 02F [1006HPA] WAS ANALYSED NEAR 20.0S 164.0W AT
270600UTC.
TD02F MOVING SOUTHEAST AT ABOUT 07 KNOTS.POSITION POOR BASED ON
HIMAWARI-8 AND GOES IR IMAGERY WITH ANIMATION AND PERIPHERAL
OBSERVATIONS. SST AROUND 27 DEGREES CELCIUS.

CONVECTION REMAINS PERSISTENT NEAR LLCC. ORGANISATION REMAINS POOR.
CIRCULATIONS EXTENDS UPTO 700HPA. TD02F LIES JUST EAST OF AN UPPER
TROUGH IN A MODERATE SHEARED ENVIRONMENT.

MOST GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND MOVE IT TOWARDS THE
SOUTHEAST WITH SLIGHT INTENSIFICATION.

POTENTIAL FOR TD02F 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.
>>>>>>>>>>>>>>>>
Rain accumulation maps from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif show easing
activity around French Polynesia, continuing activity in the Coral Sea area and
around central America, and an increase in activity over equatorial Indian
Ocean. The burst of rain west of Hawaii from a rather peculiar moving tropical
depression.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The tropical low near Rarotonga is expected to move off to the SSE and deepen
near 30S. It is expected to "steal" the winds from the French Polynesia
/Southern Cooks area and should leave behind a lingering convergence zone.
Another tropical low is in the northern coral Sea and is expected to go Se and
fade around the New Caledonia area around mid-week. Worth watching as this is a
system that may need to be avoided.
The SPCZ around Tuvalu and Tokelau may drift southwards this week, and remain
intense. There could be convective showers over Samoa and Fiji by end of the
week.
Tropical accumulated rainfall for next week may be seen at windyty.com

Subtropical ridge (STR)
The subtropical ridge are continuing to be well defined and reasonably wide,
allowing anticyclones to migrate easterly in a patterned fashion.
The HIGH which is in the western Tasman sea tonight is expected to travel east
along 30/33S this week crossing northern NZ on Tuesday /Wednesday. There may be
a squash zone of enhanced westerly winds south of this high, especially until
Tuesday, but it seems to be reasonable on north side of this high.

Another High is expected to follow across the South Tasman Sea on Tue and Wed
and then stall over central NZ on Thursday and Friday, and move off to east of
NZ this weekend.

These subtropical highs offer reasonable weather for any yachts still seeking to
get from tropics to NZ/Australia, however there are light winds in the centre of
the ridge, and there are troughs in-between the ridges, so travelling in the
winds around the back side of a passing ridge may require sailing thru a
trough-that's OK if you do it at a good latitude mid trip, but may be
disconcerting if both you and the trough arrive at the destination the same day.


Tasman Sea/NZ Area troughs.
Strong westerlies over NZ on Monday and Tuesday, then the next trough should
arrive over the weekend and linger over North Island early next week.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website www.metbob.com for information on tailor-made voyage forecasts-
Feedback to bob@metbob.com.
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==================================================

20 November 2016

Bob Blog 20 Nov

WEATHERGRAM
YOTREPS
Compiled 20 November 2016

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.

Thanks to Kevin Fawcett (of Charlotte, New Carolina) for informing me that the
Niue Yacht club website at www.NYC.NU has a webcam looking out over Alofi Wharf,
with a library of 30 minute images. If there is weather data from the airport
that is added to the image.

Our week of perigean tides from that super moon is now over. I hope you all took
adequate precautions.

SOI
The Southern Oscillation Index SOI 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.
SOI (30 day running mean) slipped into La Nina territory for a few weeks in
September and this triggered a few meteorological web sites to say "We are now
having a La Nina". Well, I'll let you judge the veracity of that: during October
it relaxed and in the past few weeks the SOI has been negative.
SOI trend (x10) since 2013 showing us in neutral territory may be seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=soi

The Ocean: The warmer the sea the quicker it evaporates, tossing water vapour
into the air, where is rises and cools into cloud. The equatorial Pacific region
hosts the widest and warmest sea on the planet. Thus its sea surface
temperatures SST may be thought of as a factor in the running of planetary
weather engine. When SST in the target zone (equatorial Pacific between dateline
and Galapagos, called NINO3.4) are notably cooler than normal, this is called a
La Nina episode.
Sea surface temperature anomaly are cooler than normal, but not yet in La Nina
territory, and may be seen at
www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthly
Compare the recent El Nino (warm seas) with its extreme predecessor in 1998.

The Tropics
The tropics are still taking a rest.
Rain accumulation maps show an increase in activity in the Coral Sea, and around
Panama, and a decrease around Fiji/Samoa. Rain maps are at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
The MJO has move out of the Pacific and is over the Americas are heading for the
Indian Ocean, so we should expect a few quiet weeks in the South Pacific
now..and activity to peak late in December.
A tropical low [1004] has formed today in Coral sea to NW of New Caledonia and
this is expected to travel south into Tasman Sea where it is expected to merge
or get captured by a deepening trough/low forming east of New South Wales on
Thursday and to travel mainly over southern NZ on Friday.
Tropical accumulated rainfall for next week may be seen at windyty.com

Subtropical ridge (STR)
The subtropical ridge is becoming stronger and wider this week.
The HIGH which is travelling east along 35S tonight past NZ and further east on
Mon/Tue/wed may briefly have a small squash zone of strong SE winds on its
northern side on Monday near 20S.
Next High in Tasman Sea is expected to form on Saturday and then travel slowly
along 30S and 35S during next week, enjoy.
These subtropical ridges offer reasonable weather for any yachts still seeking
to get from tropics to NZ/Australia, however there are light winds in the centre
of the ridge, and there are troughs in-between the ridges, so travelling in the
winds around the back side of a passing ridge may require sailing thru a
trough-that's OK if you do it at a good latitude mid trip, but may be
disconcerting if both you and the trough arrive at the destination the same day.

Tasman Sea/NZ Area troughs.
The tropical low [1004] NW of New Caledonia tonight is expected to travel south
into Tasman Sea on Monday and fade on Tuesday and merge or get captured by a
deepening trough/low forming east of New South Wales on Thursday and all this
should travel mainly over southern NZ on Friday. Associated trough is expected
to reach Opua around Friday afternoon- about the same time that I am scheduled
to give a talk about weather to the ICA seminar at Opua . hopefully it won't be
too much of a distraction, and will be over by BBQ time.

As of sailing Noumea to Australia: try and avoid that low which is expected to
form off New South Wales on Thursday morning. It looks like it may bring a
southerly buster.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website http://www.metbob.com for information on tailor-made voyage
forecasts
- Feedback to bob@metbob.com.
Tell anyone you like that to subscribe they should email me.
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.
To unsubscribe send a reply email saying LEAVE.

13 November 2016

Bob Blog 13 Nov 2016

WEATHERGRAM
YOTREPS
Compiled 13 November 2016
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.

Thanks to the generosity of 24 donors. the "weather stations for Tonga"
fundraiser at tinyurl.com/hn5k42k raised $615 in the past week, 2% of it's goal.


Many of us know there are gaps in the Google earth data. Here's a link to a
recent blog written by Max Shaw of Fluenta, introducing another app SAS Planet
(an alternative to Ovitel Maps).
See sv-fluenta.blogspot.com/2016/11/using-satellite-imagery-to-assist.html

Also Max and I have noticed that Predictwind.com has recently added ECMWF data
to their sites. I recommend ECMWF data, especially in the tropics. At present
GFS and GEM have the idea of a Low in the Coral sea by Fri 18 Nov, but ECMWF is
showing nothing there until Tue 22 Nov. ECMWF is more reliable. To learn more
about Predictwind.com's use of ECMWF data
see
www.sail-world.com/Australia/Predictwind-now-offers-European-high-quality-model-
for-forecasting/149609


And you may know that Tuesday's full moon is the closest and therefore the
largest since 1948. Tides are not exceptional. They depend on harmonics of sun
and moon gravitational forces, so having a closer moon is not a guarantee of
extreme tides-mind you if you have been taking shortcuts across a sandbar or
reef recently then take care at low tides over the next week.

The Tropics
After a few busy weeks, the tropics seem to be taking a rest for now.

>>>>>>>>>>>>>>>>>>>>>
There has been flooding, ponding and slipping around parts of New Zealand.
---and just now a severe long-lasting lateral quake
see earthquake.usgs.gov/earthquakes/eventpage/us1000778i#executive,
revised to M6.6 then M7.5, plus a tsunami warning for South Island East coast
To see the Tsunami arriving in Kaikoura and Wellington and Christchurch:
check www.geonet.org.nz/tsunami/
>>>>>>>>>>>>>>>>>>>>>>>>>

Rain accumulation maps looks less intensive rain in most areas, but an increase
around Samoa.
Rain for the past fortnight from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES

SPCZ=South Pacific Convergence zone.
SPCZ: The intensity that built up over Samoa during the past week is likely to
move towards French Polynesia this week, but in a disorganized fashion. May be
some small tropical lows forming on the zone this week with squally showers. but
models don't have anything deepening at this stage. We do have a MJO event
occurring at present but no organised equatorial westerly winds, so maybe just a
few tropical lows are likely.

Tropical accumulated rainfall for next week may be seen at from windyty.com

Subtropical ridge (STR)
Small high travelling east along 30S between Fiji and NZ tonight and moving off
to the east.
Next High in Tasman Sea is not expected until Thursday and is then expected to
travel slowly east along 30S. This is likely to be followed by a weak trough and
then another even slower and larger high next week, so this should offer a good
weather opportunity for yachts wanting to travel from tropics to NZ or
Australia.

Tasman Sea/NZ Area.
There is a parameter called SAM (Southern Annular mode) that measure the
strength of the Polar Vortex (the ring of winds around Antarctica), and when it
goes negative there is an increased chance anywhere in the Southern Ocean for
polar chilled SW winds to burst further north. It's now negative, but forecast
to turn most positive week.
See
www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/aao/new.aao_index_en
sm.html


There was a polar blast off South Africa over last few days.
And now it looks like there MAYBE a small polar blast in the Tasman Sea and off
to northern NZ on Thursday 17/ Friday 18 Nov, with strong to gale cold and
squally SW winds with huge swells.
Swells over 4 metres may extend as far north as around 26S on Friday. These are
long period swells, sometimes called gentle giants, but somewhat disconcerting
sailing, so avoid.
After Friday, there should be good sailing conditions to NZ.
As of sailing Noumea to Australia: Looks OK after the trough clears off Noumea
on Wednesday.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website www.metbob.com for information on tailor-made voyage forecasts-
Feedback to bob@metbob.com.
Tell anyone you like that to subscribe they should email me.
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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email. Or, if email wasn't from WordPress then send a reply email saying LEAVE.

06 November 2016

Bob Blog 6 Nov 2016

WEATHERGRAM
YOTREPS

Compiled 06 November 2016

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.

Weather models and weather advice depends primarily on a good network of useful
observations. I have been approached by GREG JUST on Tonga this week and he has
started a crowd-funding appeal to set up an account to add new weather stations
especially to the marine ports around Tonga and later on a few nearby Island
groups. This is a just cause (pun) and I support it. If any of you have ever
thought that I may be worthy of a bottle of wine for my efforts with this blog
or my forecasting, then here's your chance to make me proud and appreciative.

Please donate the equivalent of a bottle of beer or wine to this fund and
comment "thanks to MetBob"
I'll be watching to see just how much I'm appreciated, and you get the
opportunity to share your bottle of beer/wine for me on Facebook.Even if you
don't contribute, I'd like you to share this item with your friends.

To see the website, go to tinyurl.com/hn5k42k

A note to anyone passing thru TONGA
This is to inform all members of the public that His Majesty's Cabinet on 21st
October 2016 has approved daylight savings in Tonga and to be effective from
Sunday the 6th of November 2016 and end from Sunday the 15th of January 2017.
This time change is to extend daylight hours in the evenings to allow the public
to make better use of day light hours for economic and social activities.
At 2am on Sunday 6th of November 2016 members of the public are advised to move
their watches and clocks ahead to 3am. This notice has been copied from today's
Tongan Marine forecast at www.met.gov.to/forecast/html/FCST_BULLETIN.html

The Tropics
TC MEARI is located east of Philippines but not expected to affect land. And
there are a couple of interesting lows in the NW Pacific that are not expected
to come to much.
Rain accumulation maps looks more intensive in the Philippines area and along
the ITCZ across the Pacific, and less sin the South pacific
Rain for the past fortnight can be seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to build especially over Samoa area and by mid-week
may produce a tropical LOW that will then travel Southeast across Southern Cooks
by end of the week. The Low should carry squally showers with 30 to 40 knot wind
gusts. It may affect French Polynesia after 14 Nov. Avoid.
Tropical accumulated rainfall for next week can be seen at windyty.com

Subtropical ridge (STR)
A HIGH is travelling east across Tasman Sea along 25 to 30S from Sunday night to
be east of NZ from Friday.
Next Tasman High is a brief one on sat/Sun, crossing NZ on MONDAY 14 and
lingering east of NZ on Tue 15 Nov.
Not strong enough this week to produce any squash zones in the tropics.

This is the time of year that yachts are staging themselves in Tonga (or Fiji or
New Caledonia) and waiting for the right weather pattern for sailing to NZ or
Australia.
The Island Cruising Association are supporting the All Points Rally, from all
major parts of South Pacific to Opua ending in a seminar 16 to 26 November in
Opua.
Boats joining the rally are assisted with weather info, resources and planning
tools to help make the passage to NZ as easy as possible. On arrival
participants are welcomed to Opua and entertained with a week of entertainment
and seminars on a range of topics. This rally is FREE thanks to the assistance
of Main Sponsors Bay of Islands Marina and Boatyard and the Opua business
community. See www.islandcruising.co.nz/?page_id=717

Travel between Tropics and NZ:
The arrival times to avoid because of passing fronts are 7/8 Nov, 12/13 Nov and
16/17 November.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Follow me on Facebook at www.facebook.com/metbobnz/
See my yotpak at boatbooks.co.nz/weather.html for terms used.
See my website http://www.metbob.com for information on tailor-made voyage
forecasts- Feedback to bob@metbob.com.
Tell anyone you like that to subscribe they should email me.
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.
To unsubscribe send a reply email saying LEAVE

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