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

30 January 2010

BOBGRAM7 issued 31 Jan 2010

Issued 31 Jan 2010
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.

The South Pacific Convergence Zone SPCZ means business again this week.

The remains of OLGA are still stewing away in the heart of Australia and
turning tropical air into rain, good for a change in that part of the
world but maybe too much of a good thing in some places because it is so
slow moving. The Coriolis force should help it go south by next

NISHA came and went, sort of a one to two -day wonder. However, the
pulse of extra energy which helped NISHA to form is probably good for
other one or maybe two tropical lows. One is over Tokelau area at
present--- dominating the SPCZ and might deepen further as it tracks
southeast towards the French Polynesian area by around 3 or 4 Feb.
After that moves off, another Low may form in the Wallis/Futuna area
during the 6-7 Feb weekend.

There is a zone of westerly winds along 5 to 10S across the South
Pacific. The trade wind easterlies have shifted southwards to between
20 and 40 South. This makes the zone between 10 and 25S somewhat
lacking in wind - with the SPCZ near 10S and a counterbalancing zone of
sinking dry air along 20S - right over Fiji Tongs. This dry zone of
light winds does wander about and let the wet clouds of the SPCZ pass
through it at times, especially over Niue and Southern Cooks.

The South Pacific subtropical ridge SPSR has taken an excursion
southwards to around 40 to 50S near the dateline and become
slow-moving-held in place by the orientation of the upper flow. The
squash zone on its northern side is along 30S, between New Caledonia and
NZ, and by the end of the week the strong winds in this zone should have
built a big sea from Raoul Island to Norfolk and Lord Howe Islands.

Some fronts will attempt to punch this High away over Southern NZ on Tue
2 Feb and Sat 6 Feb but seem set to fail. The easterly winds over
northern NZ may get strong at times, including during the Auckland
anniversary day Regatta on Mon 1 Feb. A twisty trough over past day and
tonight has provided/ is providing some rain to Northern North Island,
but is likely to dry out during 1 and 2 Feb.

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