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

27 November 2010

BOBGRAM7 issued 28 Nov 2010

WEATHERGRAM
YOTREPS
Issued 28 November 2010
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.

La NINA: Southern Oscillation Index SOI over past 30 days has eased
from 1.9 to 1.5 standard deviations. The La Nina shows itself on our
weather maps with subtropical ridge being more south than normal in the
Pacific.

TROPICS
South Pacific Convergence Zone SPCZ has been active across northern
Coral Sea to Fiji and, in a more scattered fashion, from Samoa to French
Polynesia.

Moisture within the SPCZ has converged to produce a double-barrelled low
pressure system between Vanuatu and Fiji. The centre of this depression
has been moving east southeast onto Fiji, and may be named as a tropical
cyclone soon.

It has a squash zone of enhanced easterly winds on its south side that
are now around gale force. Some computers are picking that this system
should soon curve off to the south and maybe do a little loop between 25
and 30S near the 180 anti-meridian between Wed 1 and Sat 4 Dec, and then
fade and go off to the southeast.

Anyone intending to sail towards NZ this week should wait for this
system and its swells to move off first.

There was a burst of wet-season-weather on the Queensland coast around
20-22 Nov. There is some rain inland within the Australian heat trough
today and some of this may reach the Cairns Coast on 3 to 4 Dec.

A new Madden Julian Oscillation of enhanced convection is starting to
show signs of possibly reaching the Coral Sea around 10-20 December.
There is no sign yet of any equatorial westerly winds --- these usually
appear in December and can be associated with cyclone development.

SUBTROPICAL RIDGE: STR.
High over NZ today 28 Nov is expected to fade to east of NZ during
Mon/Tue 29/30 Nov.
New high moving over Tasmania at present should slowly cross South
Tasman Sea and South Island 29 Nov to 1 Dec. Then one centre may stall
in Tasman Sea and fade away Sun 5 Dec, and the other move along 40 South
to east of NZ.

NZ AREA
It's another week of high and dry (with some exceptions).

East to southeast flow is likely for Northland, between the low to north
and high to south, from Tue 30 Nov to Sat 4 Dec.

Brief troughs are likely between those highs--- one should bring a NW
flow to the South Island on Mon 29 Nov and SW on Tues 30 Nov. The next
should bring a southerly change from sat 4 to Mon 6 Dec.

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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