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

12 March 2011

BOBGRAM7 issued 12 March 2011

WEATHERGRAM
YOTREPS
Issued 13 March 2011
Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from
the patterned world of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

This weekend my thoughts and feelings are with those displaced by the
Japan quake and Tsunami. Kia Kaha.

TROPICS
La NINA is still strong, and steady. The Southern Oscillation Index
30day running mean moved from 2.19 on 5 March to 2.17 on 11 March.

There are low pressures and persistent convective rain over much of
northern and northeastern Australia, consistent with a new Madden Julian
Oscillation MJO that is now moving into the Coral Sea. It seems to be
weakening as it moves east, and there have been good trade winds in the
Coral Sea for the past week, but the coming week is likely to see
changes--- weakening winds in Coral Sea and increasing convection.

South Pacific Convergence Zone SPCZ is loosely draped over Coral Sea and
Vanuatu, coming and going over Fiji and Tonga and at present to south of
Southern cooks. Another zone is establishing itself along 10S from
Tuvalu to east of Tokelau--- this branch is likely to act as a twin of
the ITCZ around the weeks of the equinox.

SUBTROPICAL RIDGE:
HIGH1 is above 1030 and at 40S to east of NZ today Sunday 13th and
should go east. On Tue 15 March it is expected to fade at 40S but
another cell is likely to form and take over at 45S- and this cell
should head NE to get to 40S 130E by Sun 20 March. As this system
wanders east we can expect enhanced trade winds on its northern side.

A couple of sub-tropical lows are likely to form on the western shoulder
of this High-one between Norfolk and Raoul Island on Wed 16 March and
another to southeast of Rapa on Fri 18 March- these lows are likely to
be shoved off to the south-southeast.


HIGH2 from then Australian Bight should cross Tasmania on Fri 18-Sat 19
March and The South Island on Sunday 20 /Monday 21 March. There should
be an increasing squash zone of east to northeast winds between HIGH2
and lowering pressures in the Coral Sea. Avoid.


NZ Area
A front is poised to move onto southern NZ on Monday 14 March and should
weaken and stall for a few days over South Island, finally fading out
over central NZ on or around Friday 18 March.

On Sat 19 March, another front from Southern Ocean is expected to bring
a wet and chilly wind change to eastern South Island. By then a broad
trough is likely to have developed in the central and north Tasman Sea
and should sideswipe northern NZ.

On Sun 20 that trough should move off the far north as the South
Island's southerly change moves onto eastern North Island (ahead of
HIGH2).


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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