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

02 May 2010

BOBGRAM7 issued 3 May 2010

WEATHERGRAM
YOTREPS
Issued 3 May 2010
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 of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

GALAPAGOS TO MARQUESAS
There is a build up of cloud around Galapagos at present, so maybe wait
a few days before departing if you like. Take off to just north of the
equator at first, and go to around 110W, and enjoy a following current
and light southerly winds. Do not go any further north than around 30
minutes north... After 110W head direct for Nuku Hiva, the entry port
for Marquesas, and winds should obliging increase to 15 to 20 knots from
the southeast, with settled weather.

TROPICS
South Pacific Convergence zone SPCZ is having a quiet time at present,
so enjoy this while it lasts... It is slowly reorganising across the
north end of the coral sea and then in a zone from Tuvalu to Southern
Cooks, but at present reasonably clear over Samoa. Should continue to
build and hold position this week, and may spread south towards Fiji
some stage next week 10-14 May.

A LOW is expected to form at the mid-latitude end of the SPCZ to south
of Southern cooks around 6-9 May and peel off to the southeast.


SUBTROPICAL RIDGE: STR
HIGH in Tasman Sea is expected to fade near western North Island and
then be reinforced by another HIGH on Monday 3 May. New combo High
should cross the central NZ area 4-5 May and then wander off to east of
North Island on 6-7 May . There will be a squash zone of enhance trade
winds on the north side of this High mainly along about 23 South from
around Niue to New Caledonia.

Following this High there should be a trough T1 that will cross NZ on
Fri/Sat 7-8 May. Then, from 8-12 May a HIGH is expected to migrate from
central Australia along 30S across northern Tasman sea. This will build
the STR and allow for some strong westerlies south of it over NZ next
week - a step towards winter in the south.

TASMAN/NZ
Not bad for heading off over next few days, but window closes by Thu 6
May.

Mediocre cold front on Monday 3 May, High on 4-5 May, then comes that
trough T1 referred to above.
Preceded by strong northerlies on Thu 6 May and followed by disturbed
westerlies from Sat 8 May.

Some models make more of this tough than others , occasionally hinting
at chance of a low between New Caledonia and Northland early next week.
This is an unsure scenario at present, and if it impacts on your
venture then do the double-check.


TASMANIA / NEW SOUTH WALES COAST
ELLA'S PINK LADY is now on last leg of a circumnavigation, with a
solo-sailor (still under 17). For her there's one more challenge, as
that trough T1 referred to above (due to cross NZ 6-8May) crosses
Tasmania and New South Wales on Tue-Wed 4-5 may. When the trough
interacts with the east Australian current this may generate some lows,
and these will peel off to South-southeast into the southern Ocean, but
one of them may deepen rapidly east of Tasmania on Wed 5 and generate a
large zone of gales, typical of any classic Sydney-Hobart. Then that
HIGH mentioned above should kill all the wind near Sydney on the 8-9
Weekend.

The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com
Feedback to bob.mcdavitt@metservice.com

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