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

26 June 2016

Bob Blog 26 June 2016

WEATHERGRAM
YOTREPS
Issued 26 June 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.

Sea Mercy is making good progress in Fiji. Marie Dufour on cat DOMINO has
written a blog about conditions and needs in the villages they have visited,
read this at dominocatamaran.blogspot.co.nz/ and read the adventures of SV PERRY
at www.svperry.com/2016/06/the-lau-group-fiji.html#more

In the past week (the week after the winter solstice) there have been some
stormy weather around the planet. The monsoon arrived as a burst of
thunderstorms in India, with 93 people killed by lightning strikes in 2 days.
Bihar, an eastern state was hardest hit, with 59 confirmed deaths. mainly
farmers planting rice.
The Monsoon advance may be seen at www.imd.gov.in/pages/monsoon_main.php
Heavy rain has also visited South China, triggering a fatal tornado /hail storm
which claimed 98 lives in east China's Jiangsu Province. And heavy flooding has
brought widespread damage to West Virginia in the United States of North
America, killing at least 26 people.

Tropics are still having a cyclone drought.
Some tropical lows near and north of the Philippines, otherwise quiet, or so it
seems.
Last fortnight of weekly rain profiles ( from
trmm.gsfc.nasa.gov/trmm_rain/Events/big_global_accumlation.gif) shows that the
heaviest rain is now shifting east across Vietnam/South China and towards
Philippines. That's normal. The Tasman Sea area has switched from dry to wet.

WEATHER ZONES
SPCZ=South Pacific Convergence zone.
SPCZ is expected to remain draped from PNG across to the Tuvalu/Tokelau area,
then to Northern Cooks. The GFS model is picking that a trough may develop on
the SPCZ in the Coral Sea around 4/5 July and then move onto New
Caledonia/Vanuatu around 6/7 July, but this is NOT being forecast by the ECMWF
model at this stage, so can be treated as a 50% probability.

STR= Sub-tropical Ridge
STR is along 25 to 30S in Tasman Sea but more like 35 to 40S east of NZ.
The HIGH that is east of NZ near 40S and south of French Polynesia is expected
to travel slowly east along around 40S this week going towards South America.
The next HIGH over eastern Australia on Tue to Thurs is expected to fade as it
crosses the Tasman on Friday and NZ on Saturday. It will probably fade so much
that it is not going to offer a large enough gap-between-lows for yachts seeking
to depart from NZ for the tropics.

Voyage Outlooks:
Tahiti to the west
Satellite imagery shows the convergence zone over Tahiti tonight. This is
expected to weaken and shift to the north during tomorrow, bringing strong SE
winds and dry conditions to the Borabora/to Papeete area on local Monday. From
late local Monday these winds should moderate, and then there is likely to be a
dry period with light to moderate SE/E winds over the Tahiti area for the next
week or mare. That's a change from the recent wet windy weather in the area.
Since the SPCZ is expected to remain north of 15s, it appears that a voyage to
the west should travel along the drier and more settled latitudes near 17 to
19S.
Weather may not remain settled all the way from Tahiti to Tonga, as a weak
trough from the SW may travel across Tonga around 1-3 July, followed by SW
swells. So it may be desirable to stop at an Island such as Palmerston Island
or Niue /Beveridge reef along the way.

Between NZ and the tropics
MAYBE NOT this week (again), may as well stay put (again). A LOW is crossing NZ
on Monday, and then a brief ridge on Tuesday. Too brief for getting away, as
the next LOW is expected on Wed/Thu/Fri. Then another brief ridge on Saturday
followed by a LOW on Mon/Tue 4/5 July, and a front on Wed 6 July. Maybe OK to
sail north on Thu 7 July, too far away to tell.

Between Australia and New Caledonia/Fiji
OK, wait for sea to settle after Monday's Tasman Low, maybe Wed or Thursday.
Then should be Ok to sail to New Caledonia/Fiji.
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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
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