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

27 December 2008

BOBGRAM7 issued 28 Dec 2008

WEATHERGRAM
YOTREPS
Issued 28 Dec 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 are in UTC unless otherwise stated.

TROPICS
TC BILLY went offshore of Northwest Australia and deepened as it went
west into the Indian Ocean, and is now weakening away.

The South West Pacific convergence zone SPCZ has been mainly active from
Solomons to Vanuatu to midway between New Caledonia and Fiji. There has
been a side branch from around Samoa to between the Northern and
Southern Cooks. This week it looks to me that the main branch will
rebuild between Solomons and Tuvalu, and things will quieten down for a
few days over Vanuatu, but return next Sunday 4 Jan to a similar pattern
that is there today 28 Dec.

There is a Madden Julian Oscillation MJO (a boost of convection)
wandering from North Australia into the Coral Sea. This has brought
westerly winds to NW Australia, and there were a few periods of westerly
winds in the past few weeks over the Marshall Islands/Majuro, some
coinciding with high tides and causing sea flooding.

This week it seems that the winds in the Coral Sea may be light and
variable-there is a slow build up in the SPCZ and it should start
forming low pressure centres in the Coral Sea between 3 and 10 January.
Avoid the Coral Sea and its surrounds then.


SUBTROPICAL RIDGE
HIGH1 east of NZ is wandering away to the east along 40S.

A new High2 is forecast to form just northeast of NZ on Thursday 1 Jan
Tasman Sea. It may then move southeast (an unusual track for a high)
allowing a low to form on its northeastern shoulder near 35S 144W around
Sun 4 Jan, with a squash zone of enhanced winds between high and low.

HIGH3 moving into the Australian Bight is expected to cross there on Wed
and Thursday then to ridge across Tasmania and the central Tasman Sea,
reaching NZ on Saturday 3 Jan, where it may stall for a few days,
bringing high summer: settled weather for holiday makers and hay makers.

TASMAN SEA/NZ
Northwesterly flow over NZ on Tuesday and Wednesday as High1 moves
away--- showery in the west but warm and dry in the east. This
culminates in a trough crossing NZ on Thursday and Friday, damping some
New Year BBQs. Then settled weather for a while with the arrival of
High3, but there may be a low to north of NZ on Sun 4 to Mon 5 Jan much
like now Sun 28 to Mon 29 Dec, with easterly winds and onshore swells
for eastern Northland.

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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