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

24 July 2010

BOBGRAM7 issued 25 July 2010

WEATHERGRAM
YOTREPS
Issued 25 July 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.

TROPICS
South Pacific Convergence zone SPCZ is mainly along 8 to 11 South from
Solomons to Tuvalu/Tokelau. It occasionally peels away to the southeast
and makes a trough-an example of this should occur over Tonga Niue on
Sat 31 July, and this may develop into a LOW to south of Southern Cooks
early next week.

Passing mid-latitude trough occasional extend north in to the tropics.
As they pass, the trade winds weaken and get swung to be from the NE for
a while, then squalls appear, sometimes followed by a swing to southerly
winds. One of these events is near Niue tonight and should wander east
across Sothern Cooks by Tue 27 July.

SUBTROPICAL RIDGE: STR
This is stronger than normal now and further south than normal, signs of
an incoming La Nina.

HIGH 1034 budding off New South Wales on Mon 26 July should wander along
35S crossing northern North Island around Thu 29 July and reaching 150W
by Sun 1 August. A Squash Zone of enhanced trade winds is likely on
north side of the High, mainly between 15 and 10S, reaching Samoa on
Tuesday/wed 27-28 July. This squash zone is especially strong in mid
Coral Sea and across northern Vanuatu until Wed 28 July. Avoid.

TASMAN/NZ
With the incoming High, NZ is in a disturbed West to Southwest wind
flow, with fronts, on Monday/Wednesday 26-28 July; OK to good for
sailing off to the north.

After the Thursday HIGH, a disturbed flow from the NW is to be expected
over NZ, and this should wetten the West Coast and warm the East Coast,
and lead to a LOW crossing the South Island on the 31/1 weekend; good
for sailing towards Northland from the tropics, but please note this
good window closes quickly by Sun 31 July.

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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