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

23 January 2010

BOBGRAM7 issued 24 Jan 2010

Issued 24 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.

It looks to me that we are about to enter the business part of the
cyclone season.

TC OLGA came from an extra burst of convection that started over Solomon
Islands and followed the path as described in last week's weathergram,
and seems to have temporarily cleared the Coral Sea of its clouds... It
may go thru a reintensification in the Gulf of Carpentaria on Monday 25
Jan and bother people south of Darwin on Thursday 28 Jan.

The South Pacific Convergence zone SPCZ has reformed in its normal El
Nino position from around Tuvalu to Tokelau, between Northern and
Southern Cooks and across southern French Polynesia. Something
different about it this week is the likely appearance of a zone of NW
winds on its northern side especially in the zone between Samoa and the
Cooks. This is likely to make the area between Samoa and Niue a
breeding ground of tropical lows in the next week or so. Computer
models are struggling to resolve exactly where these tropical lows may
form, and it could be around the Rotuma/Futuna area. Any low that forms
is most likely to track southeast-wards towards Niue. Avoid and keep

A new cell in the South Pacific Subtropical Ridge SPSR is moving across
South Island on Mon 25 Jan --- then moving further east along 40S past
Chathams on 26-27 Jan - It will continue eastwards along 40/45S, so that
early next week there will be around 50 hPa of isobars between its
centre and the centre of the Low coming south form the Niue area, making
for a large and intense squash zone between 30 and 40S well to east of
NZ. This squash zone should generate large swells which will be
arriving along North island east coast.

Surfs up for Auckland's anniversary weekend right thru to Waitangi Day.

The arrival of that cell in the SPSR marks an end to the recent
unsettled weather and the beginning of a week or more of summer-like
conditions just as we approach the period of the year that normally has
the warmest days.

For South island it looks to be a week of warm maybe muggy northerly
winds, mostly dry so prepare for an increasing fire risk.

For North Island's north half, the humid easterly turning northeast flow
should bring some welcome showers, especially during their
anniversary-holiday weekend 30 Jan to 1 Feb when a trough may add a
clockwise twist to the wind flow.

South end of the North Island has a dying southerly for its anniversary
holiday on Mon 25 Jan and then a humid northerly for the rest of the
week, varying between sunny and cloudy, and adding several degrees to
the overnight low. Summertime, at last.

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