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

28 February 2009

BOBGRAM7 issued 1 March 2009

WEATHERGRAM
YOTREPS
Issued 1 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
A jetstream over the South Island of NZ provided the impetus for the
rapid deepening of a low near Northland late Friday resulting in a wet
warm front crossing the North Island in Saturday. Accompanying easterly
winds were strong enough to dislodge several tents at Northland Fieldays
so that the (my) Saturday show was cancelled, also Lionel Ritchie's
Mission Estate concert in Hawke's Bay. Rotten timing, even Derby day in
Auckland was put off until today.

TROPICS
The South Pacific Convergence Zone SPCZ is only slowly reforming after
it was drained off a week or so ago. There are two main zones of
convection-one from Solomons to Tuvalu, weak over Samoa and then
stronger again over Northern Cooks and French Polynesia. T'other zone
lies from northern Queensland to New Caledonia and is currently
extending southeast towards the Kermadecs.

Not much action expected in the tropics this week, but southeast winds
should be strong at first on the south side of that SPCZ. that's roughly
from Kermadecs to Queensland until Wednesday (squash zone). Another
squash zone of enhanced easterly winds is likely between Southern Cooks
and Tonga from Wednesday to Saturday UTC.

TASMAN SEA
HIGH crossing the Tasman Sea on Monday and NZ on Tuesday is forecast to
intensify to over 1030 east of NZ by Wednesday. Light winds and settled
weather within this high, but a strong squash zone of easterly to NE
winds is expected over northern NZ when the HIGH moves off late
Wednesday and on Thursday.

On Thursday, a family of LOWS is likely to form off south-eastern
Australia and east of Tasmania. The frontal rain band (between the
departing HIGH and these new Lows) should reach northern NZ on Thursday
and cross NZ on Friday/Saturday.

This time it will not be jet assisted so shouldn't be as wet/windy as
the 27/28Feb, but something to interrupt the Auckland Boat show - I'll
be there and I have some free entry passes for Thursday/Friday , let me
know by return email if you are interested.

These Lows may amalgamate to one centre that may deepen to 970 as it
swings past Campbell Island on Sat 7 March - close enough to bring gale
to storm conditions for the start of the weekend to Foveaux Strait,
keeping the Bluff fishing fleet in port for a while at the start of the
new Oyster season.

OUTLOOK:
After this Low has moved off, on Sunday 8 March, another HIGH is likely
to cross the Tasman Sea / NZ area bringing a few days of settled
weather.
Next lot of tropical lows will probably form when this HIGH moves off to
the east after 10 March.

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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