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

29 November 2008

BOBGRAM7 issued 30 Nov 2008

Issued 30 Nov 2008
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 below are given in UTC unless otherwise stated.

South Pacific Convergence Zone SPCZ has had a quiet time recently---
some strong convection near Marquesas and with an upper trough crossing
Tonga, but otherwise quiet.

SPCZ is likely to be active in the zone from Northern Cooks to
in-between Marquesas and the main part of French Polynesia and to move
south this week.

Indications are that the SPCZ may slowly pick up in activity between
Solomons and Fiji during the coming week.

In particular a tropical Low with slack winds near its centre is likely
to form over Northern Cooks on 1-2 Dec and then drift west and south,
crossing Niue and Tonga on 3-4-5 December and then maybe deepen over
Kermadecs on 6-7 Dec. Slack winds near the centre but there should be a
squash zone of enhanced easterly winds on the south side of this low---
worth avoiding--- this squash zone is expected to reach its peak near
Kermadecs/Minerva between 5 and 8 Dec.

Not much expected on western side of this low, but be on squall watch
when on its eastern side

Upper air flow around the planet has set up long roller coasters that
are encouraging higher than normal pressures in the subtropics between
120 and 180 W and lower than normal pressures in the Tasman Sea area.


Fronts and lows are growing well when crossing the Tasman Sea, then
fading as they cross NZ.

On Mon 1 Dec a Low should cross the South Island, followed by a westerly
flow on Tuesday.

On Thursday a front should cross Tasman Sea/NZ, proceeded by a NW on
Wednesday, and then followed by a SW flow and a brief ridge on Fri.

A similar pattern repeats on 6-7-8 Dec, but with a bigger ridge.

So it is a bit like a trampoline in the Tasman this week, try and jump
in rhythm with the weather.

The terms used are more fully explained in the METSERVICE Yacht Pack.
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