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

20 November 2010

BOBGRAM7 issued 21 Nov 2010

Issued 21 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.

South Pacific Convergence Zone has been active across northern Coral Sea
to the Wallis/Futuna area and then stretching off to the southeast of
Tonga. A small tropical low near Wallis/Futuna tonight should fade on
Monday, broadening the trough over and to south of Tonga.

When the cold Southerly winds that are crossing New Zealand tonight
reach this trough over the Kermadecs on Wed 24 Nov --- this is
expected to promote a rapidly deepening and slowly-south-moving Low from
Thursday 25 to Sat 27 Nov--- making for strong southerlies between NZ
and Tonga from 22 to 26 Nov.

So, those staying in Tonga waiting for a comfortable sail to NZ should
keep waiting - may be a brief window around 27-29Nov, but please

There's a new branch of the SPCZ budding off the Queensland Coast.
Since we are in the early part of the Cyclone season and have a strong
La Nina, it is to be expected that the SPCZ will spend much of its time
in the Coral Sea, so we can expect this new branch to activate over the
Coral Sea this week, lowering the pressure there. And since there's a
High stalled in the Tasman Sea, the result is a squash zone of enhanced
SE winds along 20 to 25 S this week, especially over New Caledonia.

Computers are picking that tropical Low should form on this SPCZ in
eastern Coral Sea around Wed 24 Nov and this should then deepen as it
crosses Vanuatu on Fri 26/Sat 27 Nov and weaken to south of Fiji by
Tuesday 30 Nov. Avoid this Low and, if in Noumea, consider waiting out
this squash zone.

That large High stationed at 35S to South of French Polynesia should go
off to 40South and fade away by Wed 24 Nov.

A new high is filling the Tasman Sea during Monday 22 Nov. This should
hold itself there until it fades on Sat 27 Nov... and it should also
squirt a ridge across central NZ and Chathams Islands by Wed 24 Nov that
should go east around the south side of the Low near Kermadecs.

Cool SW flow over NZ tonight (touch of snow in the Alps) turning
southerly on Monday 22 Nov.

The Stalled Tasman High keeps surrounding features away from NZ this
week, but a trough should be in place over Southland by the weekend in
readiness to move onto NZ early next week when the High fades.

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