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

14 June 2009

BOBGRAM7 issued 14 June 2009

WEATHERGRAM

YOTREPS

Issued 14 June 2009  

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 are in UTC unless otherwise stated.

 

TROPICS/SUBTROPICS

The South Pacific Convergence Zone SPCZ spent last week in two, each at a limit.

 

The eastern part moved to the northern limit of the SPCZ and stretched from Tuvalu to French Polynesia.  It isn’t often that the SPCZ moves north across French Polynesia, but that did happen last week.  That zone is now weakening away.

 

The Western part ran along the southern limit, and stretched fro Coral Sea to NZ.  It watered the paddocks we parked in during National Fieldays and I was somewhat concerned my 2-wheel drive would get bogged, as some did. However, parking sensibly worked and I’m back in Auckland now.

 

During the coming week that western part is expected to become the main SPCZ.   It is now stretching from northern Vanuatu to Fiji/Tonga and should peel off to the southeast on Tuesday /Wednesday, but redevelops over Fiji/Tonga on Friday /Saturday.

 

The main development in the SW Pacific topics this week is expected to be the formation of a new LOW between New Caledonia and Lord Howe Island (sort of over Chesterfield reef) on Friday.  This LOW is expected to then take a SE track and be between Raoul Island and North Island by mid next week, steeling wind from the New Caledonia to Tonga area   Avoid.

 

The Galapagos to Marquesas route is all quiet now. .

 

SUBTROPICAL RIDGE STR / NZ WEATHER

HIGH currently in N Tasman Sea should fade away by Tuesday, and a new HIGH is expected to gel from along the Aussie Bight coast over Tasmania at 1030 on Tuesday.  This HIGH peaks as 1032 in mid Tasman on Saturday and then weakens slowly to 1020 over central NZ next week, whilst that sub tropical low swings by further north.  Avoid the squash zone of enhanced easterly winds between HIGH and Low.

 

Over NZ I suppose the highlight of the week comes from the south …we have a SW flow over the country at present, and a low in the southern Ocean is combining with that gelling HIGH in the Aussie Bight to shovel a southerly onto South Island tonight and Monday.  Not much moisture but cold enough to bring some snow to our higher roads and ski fields.

This cold southerly gets focussed onto eastern North Island on Tuesday as a new Low forms near 44S 170 to 175W whilst that new HIGH hits Tasmania. For the remainder of the week we should have a easing S to SW flow as that HIGH approaches.

 

 

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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