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

14 March 2009

BOBGRAM7 issued 15 March 2009

WEATHERGRAM
YOTREPS
Issued 15 MAR 2009
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.

LAST WEEK
HAMISH did as it was told. JONI was something of a surprise, springing
up out of that disorganised convection over the Cooks and shooting off
to the southeast.

TROPICS
The South Pacific Convergence Zone SPCZ remains active over northern
Australia. Today's output from the EC model is picking another tropical
cyclone in the Coral Sea from Sat 21 to Wed 25 March and the NOGAPS
model is picking two or three tropical develops in the Indian Ocean
during the coming week, and all this is in spite of nothing showing up
in the parameters measuring the MJO pulse. Basically it is still
cyclone season even if the equinox is happening on Friday (UTC).

SPCZ is also active from Solomons across Vanuatu and onto Fiji,
especially from Monday to Wednesday. Another branch of disorganised
convection is hovering over the Cook Islands and occasionally touching
parts of French Polynesia. Some computer models are picking that a
tropical Low may form over Tonga or New Caledonia on Thursday or Friday
- but I'll vote for the EC model which has a TC forming in the Coral
Sea.

SUBTROPICAL RIDGE/TASMAN SEA/NZ
A large HIGH 1030 is over Chathams today (15th) and moving off to the
east. It should extend along 40S and weaken when it is south of the
Cooks on Wednesday 18th. Between now and then there will be enhanced
easterly winds on the northern side of this HIGH, between 25 and 35S - a
squash zone.

Following this HIGH is a LOW --- on Monday 16th this LOW drops to around
998 hPa over Tasmania. It should track east the southeast and then it
deepens again on Thursday 18th over Campbell Island. Its associated
front crosses NZ on 18th and 19th. Avoid, but nothing major.

And following that LOW is another HIGH, rather weak at around 1022,
moving across New South Wales on 17-18 March. Days and nights are now
getting of equal length, and consequently the subtropical ridge is
starting its annual migration northwards, and this HIGH takes a track
further north than its predecessor. This HIGH is likely to weaken into
just a ridge and cross NZ on 20-21-22 March. There will be a strong
squash zone between this HIGH and that Low in the Coral Sea, from 19
March onwards, mainly 20 to 25S. Avoid.

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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