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

30 August 2009

BOBGRAM7 issued 30 Aug 2009

WEATHERGRAM
YOTREPS
Issued 30 August 2009
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas come from
the patterned world of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

TROPICS/SUBTROPICS
Looks as though it is the peak of the cyclone season now in the Northern
hemisphere with activity in the western and eastern North pacific and in
the Atlantic... but I think TC Danny will weaken offshore as it heads
along the Gulf stream... maybe making landfall over Nova Scotia
something like Bill did.

As for the South pacific - well, the main part of the South Pacific
convergence Zone SPCZ remained in a northern-most position last week and
is likely to do so this week as well (this is where it liked to be in El
Nino) from Solomons to Tuvalu to Tokelau, and from there it forks with
one section along Northern cooks and French Polynesia and another
section across Southern Cooks.

There is likely to be a tropical trough forming over Fiji around wed 2
sep UTC (they had dry weather there during Hibiscus festival last week,
so this trough may bring some welcome rain). This trough is likely to
wander east, propelled along by westerly winds aloft. It should reach
Southern Cooks area by sun 6 sep UTC. Windy wet northerlies precede
this trough , and as it makes its way east wards across the tropics it
will kill the trade winds, and may even be followed by s cool dry
southerly for a few days. Time yourself around it.


SUBTROPICAL RIDGE
A HIGH that is today south of Niue is wandering east along 30S. An
associated squash zone of enhanced trade winds is today from around
Suvarov to Samoa and this squash zone will track east along the north
side of the HIGH and reach French Polynesia around Thu 3 Sep UTC and
then fade.

Next High is expected to build in the central Tasman Sea on Wed 2 Sep
UTC and cross NZ on Thursday at around 40S and then fade in the south
and retract to the normal 30S latitude.

TASMAN/NZ AREA
Unusually intense front is crossing NZ tonight, along with a companion
LOW sliding south out of the Tasman Sea.

A weaker front is expected on Tue 1 Sep, however that front is expected
to deepen into a big LOW near the dateline/40S on Thursday/Friday... and
that development, in cahoots with a HIGH in the Tasman should feed a
cold southerly flow onto eastern NZ especially on late We3d, Thu, and
early Fri.

Next front is likely on Sat 5 Sep UTC, and this front may linger when it
reaches the north Tasman Sea, waiting for a LOW to deepen in the Tasman
early next week.

So it's a week of possible weather windows for sailing in all direction
around NZ, and, after tonight's front, the strong winds should stay away
for a while (but avoid the southerlies on the Hawke's Bay coast on
Thu/Fri).


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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