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

25 September 2016

Bob Blog 25 Sep 2016

Bob Blog 25 Sep 2016
Posted on September 26, 2016
WEATHERGRAM
YOTREPS
Compiled 25 September 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.

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) has slipped into La Nina territory during past two
weeks. It was above 10 units on this Australian scale. If it can hold this high
for a month in a row the we can say we are having a La Nina.
SOI trend (x10) since 2013 showing us in La Nina 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) are notably cooler than normal, this is called a La Nina episode.
Sea surface temperature anomaly may be seen at
http://www.farmonlineweather.com.au/climate/indicator_enso.jsp?c=nino34&p=monthl
y
We now have cooling seas in the target area, and there MAY be a weak La Nina in
the next few months

The Tropics
TC MEGA is in the NW Pacific, there are two tropical systems between Hawaii and
Mexico, and TC KARL and LISA are in the North Atlantic.
Cyclone tracks seen on ruc.noaa.gov/tracks/

Rain for the past fortnight may be seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
and these rain accumulation maps show an increase in convection over Indonesia
and Philippines from the west, and an easing in convection over the South
Pacific.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to stay quiet in the Solomon islands to Tokelau area
No squash zones. A Passing trough may affect from Tonga to Niue late in the
week.

Subtropical ridge (STR)
This is expected to remain weak and along about 20 to 30S.It is NOT often this
far north and is weakening all the trade winds, offering rare opportunities for
getting east in an Island hopping fashion if you like.
Rain accumulation may be seen at windyty.com
Next High is expected to spread to east of NZ from the SOUTH after Wednesday,
shovelling polar chilled southerly winds northwards so that they deepen a LOW
near 35S 165W late in the week. Avoid travelling direct between NZ and Tahiti.

Travel from Tahiti to Tonga:
The weak winds that have been affecting Tahiti recently should be over from
tomorrow. Go for it. No squash zones, and no strong convergence zones, but
voyages are likely to encounter a passing trough with maybe some showers and
varying winds for a day or two. It is looking OK to venture via Suwarrow this
week.

Travel between the Tropics and NZ:
A series of LOWS continue to travel across Tasman Sea/Northern NZ area over next
10 days, with a brief break for a passing ridge on Thu/Fri. These lows are not
really making gales, but the fronts do have strong winds. Avoid
arrival/departure on Sat 1 Oct or Thu 6 Oct.

Travel between New Caledonia and Australia:
Intense TROUGH crossing north Tasman sea on Mon 26 Sep, then OK weather for
Australia to New Caledonia. Another intense trough in N Tasman sea on Thu/Fri
29/30 Sep to avoid.
As for getting form New Caledonia to Australia: not this week, too much
headwind, and probably not next week. Maybe OK from around 8-10 Oct.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.

18 September 2016

Bobgram issued 18 Sep

WEATHERGRAM
YOTREPS
Prepared 18 September 2016 NZST

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
TC MALAKAS is heading for Japan and JULIA is off to Florida and the Carolinas
whilst KARL should stay offshore in the Atlantic. Cyclone tracks may be seen on
ruc.noaa.gov/tracks/

Rain for the past fortnight can be seen at
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
They show an easing in activity everywhere.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to remain steady in the Solomon Islands to north of
Fiji area.
Rather weak further east.
A Passing trough may affect from Niue to Southern Cooks during the week (after
Tuesday local).

Subtropical ridge (STR)
This is expected to remain weak and along about 25 to 30S.
Net High is NOT expected to enter Tasman Sea until around 1 Oct.

Travel from Tahiti to Tonga:
No squash zones, and no strong convergence zones, but voyages are likely to
encounter a passing trough with maybe some showers and varying winds for a day
or two. It is looking OK to venture via Suwarrow this week.

Travel between the Tropics and NZ:
Remember that NZ changes to NZDT next Sunday 25 Sep.
A series of LOWS are expected to travel across Tasman Sea / Northern NZ area
over next two weeks with lows crossing Northland on Wed 21, then next on Sat/Sun
24/25 Sep then wed/tue/fri 28/29/30 Sep, then maybe Sun 2 Oct.
Try and arrange arrival in NZ BETWEEN these lows.

Travel between New Caledonia and Australia:
Too many lows crossing the Tasman sea next two weeks. Maybe try again when that
IGH arrives around early October.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

11 September 2016

Bob Blog 11Sep

WEATHERGRAM
YOTREPS
Prepared 11 September 2016 NZST
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.

Northland Radio
Northland Radio has moved to a Facebook page so everybody can view it.
Please tell your cruising friends. it's at www.facebook.com/northlandradio.nz/
And Schedule is at www.northlandradio.nz/frequencies/

The Tropics
TC MERANTI is heading for the China Sea and ORLENE is off the Mexican West
Coast.
There is a tropical depression in the Gulf of Mexico-not expected to make
landfall,
and are several in the Atlantic with one that may reach UK by end of the week.
Cyclone tracks may be seen at ruc.noaa.gov/tracks/

RAIN around the tropics:
Rain for the past fortnight from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif
show an easing in activity over Indian Ocean, but much the same in South West
Pacific.

WEATHER ZONES
Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing
wind, isobars, current, swell black arrows / Sig wave height purple lines, swell
and wind waves, SPCZ and STR.

SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to remain strong in the Solomon Islands to north of
Fiji area, with a burst of activity along 10S between Tokelau and Northern
Cooks. The SPCZ is likely to pass across Fiji and Tonga /Niue around early to
mid-week (as seen at windyty.com using Rain accumulation).

Subtropical ridge (STR)
High that is over North island tonight is expected to stretch out along 35S to
east of NZ this week. It is somewhat of mediocre intensity, and that's good news
for there isn't really any associated squash zone on its northern side in the
tropics.
Next HIGH is NOT expected to travel into Tasman Sea until mid-next-week.

Travel from Tahiti to Tonga:
Voyage along about 20S is likely to encounter the passing SPCZ around local wed
to Friday 14 to 16 Sep, and that may be squally.
It is looking OK to venture via Suwarrow this week.

Travel between NZ and the Tropics:
Over northern NZ expect NW winds ahead of a front travelling on Fri 16 Sep,
maybe OK for arrival.
But avoid arriving Sat /Sun 17/18 Sep when there is a front or Mon 19 Sep when
the maybe a gale change to SW winds.
Then OK to arrange departure so as to arrive with a ridge of light winds wed 21
Sep--- such a voyage may go thru a front near 32S but with no more than 25 knots
for a brief time, possibly an acceptable compromise.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
To unsubscribe send a reply email saying LEAVE.

04 September 2016

Bob Blog issued 4 Sept 2016

WEATHERGRAM
YOTREPS
Issued 4 September 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.

A few weeks ago I pointed out that a lot of the detail on Google earth over the
tropical oceans is missing as a data-saving tactic. See "Google lacunae" at
metbob.wordpress.com/2016/08/15/bobs-blog-11/

Since then Tom Partridge of Yacht Adina has seen my comments and been in touch.
He has written a much more detailed and thorough account of navigating with
satellite imagery for Yachting Monthly's May 2016 edition. This article is now
free online and he has kindly given me permission to share a link to his blog
with you at
www.yachtingmonthly.com/sailing-skills/how-to-make-navigation-safer-using-satell
ite-images-34665
.

++++

Last Friday morning there was a M7.1 quake to NE of our East Cape.
This caused a 30cm Tsunami which was recorded via our tidal gauges network in
their "detided" data:
at www.geonet.org.nz/tsunami/
Remember this link so you can track the waves is the next New Zealand Tsunami.

++++++++++++++++
The averaged isobar pattern for the past month may be seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30.fnl.anim.html
And the variation from normal may be seen at
www.esrl.noaa.gov/psd/map/images/fnl/slp_30a.fnl.anim.html
The most significant features are the lower that normal pressure over the arctic
and higher than normal pressure over the Antarctic.

The Tropics
TC NAMTHEUN is over Japan, LESTER is moving off to the north of Hawaii, and
HERMINE is travelling away from New York after bringing a deluge of rain to
eastern USA states, There are also a few possible tropical lows, labelled
GENESIS in this map, which may affect some areas later this week.
Cyclone tracks seen on ruc.noaa.gov/tracks/

RAIN around the tropics:
Rain for the past fortnight from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.tif
The rain maps show an intensification in the intensity of rain in the South
Pacific.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to remain strong in the Solomon Islands to north of
Fiji area, and may weaken further to the east.

Subtropical ridge (STR)
High that is shown to be in western Tasman Sea by Wednesday is expected to
travel northeast, crossing northern NZ on Sat/Sun 10/11 Sep and then moving east
along 30Sto east of New Zealand from Monday 12 Sept. There is likely to be a
zone of strong enhanced trade wind (over 35 knots) from Tonga to Vanuatu on 10
or 11Sep, associated with this passing High.

Travel from Tahiti to Tonga:
Voyage is likely to encounter the north end of a passing trough on local sat 10
Sep (variable winds and some showers), and then there may be a squash zone of
strong SE winds around Tonga on or around 11 Sep.
It is looking OK to venture via Suwarrow this week.

Travel between NZ and the Tropics:
Front part of trough went across North island Sunday night and is expected to
weaken as it goes north, it may bring a moderate wind change and some showers to
Tonga on Thursday.
Ahead of the rising pressures of the HIGH mentioned earlier, a TROUGH is
expected to cross Northern NZ on local wed night, followed by strong cold SW
winds. During Thu/Fri 8/9 Sep winds over NZ should swing from strong cold SW
wind to strong cold southerly, finally easing over Northland on Sat 10 Sep.
Try to avoid this strong wind change. it is expected to travel north on
Thu/Friday and reach Tonga as strong S/SE winds in a squash zone on Sun 11 maybe
late Sat 10Sep.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
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.
To unsubscribesend a reply email saying LEAVE.

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