BOBGRAM7 issued 9 May 2010

WEATHERGRAM
YOTREPS
Issued 9 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
Take off to just north of the equator at first, and go to around 110W,
and enjoy a following current and a light southerly wind. 110W marks
an area of squally showers this week. After 110W head direct for
Marquesas (Nuku Hiva or Hiva Oa) and winds should obliging increase to
15 to 20 knots from the southeast, with settled weather.

TROPICS
South Pacific Convergence zone SPCZ is starting to reactivate this week
after a quiet time. It stretches across Papua New Guinea and Solomons to
northern Vanuatu, and this branch is expected to stretch to be across
Fiji and Tonga on Tue/Wed 11/12 May There is another branch from east
of Samoa to Southern Cooks, and this is likely to take a rare wandering
onto French Polynesia on Thu/Fri 13/14 May.

SUBTROPICAL RIDGE: STR
HIGH1 that moved east of New South Wales over the weekend is being
shunted over central New Zealand on Mon 9 May and should wander steadily
eastwards along 40S to east of NZ for the remainder of the week, with a
squash zone of enhanced trade winds on its northern side that should
affect southern Cooks from Wed 12 to Sun 16 may.

Then the STR goes through a weak period. The next High is expected to
wander across the eastern Australian Coast line on Sat/Sun 15/16 May,
just in time to kill the wind for Ella's Pink Lady as she arrives in
Sydney.

A small wedge of this ridge may get east along 22-23S to New Caledonia
and south of Fiji on 15/16 May and that will be preceded over New
Caledonia and Fiji by a period of light southerlies and clearing weather
on 12-14 May

TASMAN/NZ
Weather window for comfortable sailing out from Northland is closed this
week.

Low1 to northwest of Northland has to wait for High1 referred to above
to get east. So it's doing a loop tonight/ Monday and should then
travel south along 170E on Tue/Wed 11/12 May, fading as it crosses
Southland.

Around this time a large trough is expected to cross Tasmania, followed
by a very cold southerly that will be originating from the Antarctic ice
shelf- a polar outbreak. This trough should form a new low in mid
Tasman Sea on Thurs 13 May, and this low should cross central NZ on 14
to 16 May, with that polar outbreak fading as it arrives over the
southern South Island on Fri 14 May.

When a Low deepens like this in the Tasman Sea as it approaches central
New Zealand, it is able to draw in moist warm air and cool it with fresh
cold air: this is a well-known scenario for rain in NZ, so take time
out to clear those gutters of autumn leaves in readiness.

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