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

22 November 2008

BOBGRAM7 issued 23 Nov 2008

Issued 23 Nov 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.

Well, the troughs in the Hot Aussie interior DID make their stormy way
across Brisbane early last week and have formed a front and Low in mid
Tasman Sea.
The HIGH that crossed NZ has formed a reliable wind at last for yachts
heading from Tonga to NZ and it arrive on Wed 19 as picked in the last
Weathergram. Good to sea the weather unravel according to plan.

The trough moving from central Aussie to central Tasman Sea has turned
the winds in the Coral Sea to a NW flow. It will take all week for the
trade winds to return there. And maybe that's it for the strong trade
winds that have been bothering the Coral Sea over the last few months.
This transition is something look a seasonal transition... it has
allowed westerly winds and thunderstorms to reach Darwin--- the start of
the wet season perhaps. .. There is now a Madden Julian Oscillation
occurring over Indonesia along with some equatorial westerly winds
around Papua New Guinea. This should all drift east and we can expect a
boost in the activity of the South Pacific Convergence zone (SPCZ)
between around 10 to 20 Dec, increasing the chances of a Tropical
Cyclone in the South Pacific around mid December.

South Pacific convergence Zone SPCZ remains in a zone from Solomons to
Wallis/Futuna to Northern Tonga/Niue. Another smaller zone extends from
Tuvalu to Northern cooks. The computer models are indicating that the
SPCZ may shift south and west towards Fiji by the weekend of 29 to 30
Nov. Rain rather than wind, but there may be a small squash zone around
Minerva / Kermadecs late in the month.

High is expected to linger to east of North Island until Tue 25 Nov.
Then a blocking High settles near 40S to south of French Polynesia for
the rest of the week--- there will be a squash zone of easterly winds
along 20S between French Polynesia to Niue for much of the week, good
for sailing west.

That Tasman Low and its frontal systems is crossing NZ early in the
week, but fading as it encounters the lingering High. Nothing major for
anyone sailing to Opua, but remember to allow for the post-frontal SW
flow on Tuesday.

Next High should bud over southern Tasman Sea on Wednesday and then move
Northeast to north of NZ on Friday.

Next trough should bring a southerly buster to Sydney on Friday and
deepen rapidly into a LOW in South Tasman Sea on Sat 29 Nov then cross
southern NZ on Sun 30 Nov. Avoid.

Weather is looking settled for the CANANZ Boat Show open day at X Marina
at Westhaven in Auckland 0900-1500 Sunday 30 Dec - free entry, BBQ and
prizes, open to anyone (in Auckland) - ask for me.

The terms used are more fully explained in the METSERVICE Yacht Pack.
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