Bob McDavitt's Weathergram

WEATHERGRAM YOTREPS
Issued 15 June 2003

Bob McDavitt's ideas for South Pacific sailing weather.
(Standard disclaimer: Weather is a mix of pattern and chaos,
these ideas come from the patterned world of isobars, so please
do your own fine-tuning).

As we approach the shortest day the SW Pacific seems finally to
be settling into a more standard winter pattern this week – with
SPCZ still active over PNG and Solomons then snaking in a weaker
way southeast to Fiji then north to Tuvalu /Tokelau and then
southeast to Southern Cooks. Another active zone lies near
Marquesas with occasional activity over French Polynesia. Highs
are enlarging over the Australian interior but shrinking as they
advance across the Tasman Sea, generally between 30 and 35S. The
hotter hemisphere is now the Northern Hemisphere and GINA/EPI are
just memories.

The Low that deepened just east of the North island last Monday
(giving a good southerly to the North Island) joined with the
remains of GINA and held fast at 170W for several days so that
the High following it had to go south to banana around it. This
procedure is still occurring and the High should pop back north
to 35S when it reaches 140W late in the week, and as the low
fades. The squash zone easterlies between these systems is
generating good swell for surfers on East coast of the North
Island, but avoid sailing in it. And after Tuesday, as the low
fades, a new high should build near 35S 160W maintaining healthy
trade winds from Rarotonga to Vanuatu.

A new trough is now crossing NZ with several lines of activity.
The best day to leave Northland for points-north is late
Wednesday (local).

A low is expected to move onto SW Australia late in the week.
This should displace a ridge of the High that is normally there
down to south of 40S and allow it to ridge onto the iceshelf.
This should displace some polar chilled air northwards (in a sort
of dam-burst fashion), going around a low in the southern ocean
and washing onto NZ with SW winds about Friday 20th. Good snow
in time for the shortest day (22 June).

The terms used here are more fully explained in the METSERVICE
Yacht Pack. Feedback is encouraged to mcdavitt@metservice.com -
Bob McDavitt
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