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

26 October 2008

BOBGRAM7 issued 26 Oct 2008

WEATHERGRAM
YOTREPS
Issued 26 Oct 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 below are given in UTC unless otherwise stated.

TROPICS

Nov to April is the period described as Cyclone season for the South
Pacific. Most Insurance companies do not pay out on any storm damage to
yachts in the South Pacific during this period, so that's why early
November triggers a migration of yachts out from Tonga and Fiji.
Climatologists looking at the coming cyclone season are expecting, on
the basis of the sea surface temperature trends, that it should be
average (8 to 10 named systems) with a slight drop in risk east of the
date line and a slight increase in risk for the Tasman Sea/NZ area.
Normally the first cyclone appears soon after equatorial westerlies
arrive over the Papua New Guinea/Solomons area... the Monsoon is active
over Indonesia but there is no sign of these westerlies, so my pick is
that the first cyclone is something like six weeks or more away.

South Pacific convergence Zone has been stationed from Papua New Guinea
across Coral Sea to Vanuatu/ New Caledonia in past week and
intermingling with a mid-latitude trough that crossed New Zealand.
Another branch has been coming and going in the Samoa area.

Not much change expected in the SPCZ this coming week, but some
activity is expected between Tuvalu and Vanuatu early this week.

SUBTROPICS

I received an email from a yacht near the dateline and 30S on Saturday
reporting 30 knot westerlies and 8 metre swells. So my weather gram
last Tuesday was worthwhile following. The trough is still lingering
over Kermadecs today and may bring some squalls to the Minerva area on
Tuesday or Wednesday.

Subtropical ridge is likely to be draped along 30/33S between 160W and
160E all this week until Sun 2 Nov. Slack winds and left over clouds
in this zone, but SE winds are likely to often be over 20 knots between
20 and 24 South, including Minerva reef.

TASMAN SEA / NZ AREA and the All Points Rally

With the annual yachting migration about to occur there is also the All
Points to Opua Rally of the Island Cruising Association, mainly from
Pangaimotu (Tonga)/Musket Cove (Fiji)/Vila (Vanuatu)/Isle des Pins (New
Caledonia) to Opua, starting 1/2/3 Nov.

There isn't much dramatic happening in the weather, but anyone leaving
Fiji/Tonga before Wednesday will likely need to go on squall watch
during Tuesday/Wednesday near 22 to 24South.

Early next week, around Monday 3 November, as a front crosses the North
Island, a small Low is likely to form on this front. This Low then
likely grows and fades when it is east of the North Island on 4 to 6
November... making for several days of SW flow over Northland.

So maybe your strategy will be to time your arrival in Opua after this
SW - or maybe sail so you take them as side-on as you can. It's hard to
tell this far out, but current indications are that the SW winds near
Opua are likely to be strongest 4-6 Nov.

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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