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

03 October 2010

BOBGRAM7 issued 3 Oct 2010

WEATHERGRAM
YOTREPS
Issued 3 October 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
SOI (90 day) is now 2.15, up 6% from last week, so La Nina is just
getting stronger. It now has values not seen since 1988. NZ's NIWA
Institute will be meeting to consider what this means for the coming
cyclone season, and I shall hold fire with my comments until after that.


TROPICS
South Pacific Convergence zone is mostly found at around 10S, but did
take an excursion across the Coral Sea during last week-touching New
Caledonia briefly.

There is an upper trough over the Suwarrow to Niue area slowly surfacing
to south and east of its axis. It's thundery. Should develop a LOW to
east of the Kermadecs on Mon 4 Oct that will move off to the SE then
stall around Thu 7 Oct.. The tropical extension of the trough will
likely kill the winds over the Cooks this week, and may even turn the
surface winds to a weak westerly, along with cloud and rain. SO it
isn't a good week to "puddle jump" westwards from Tahiti.

SUBTROPICAL RIDGE: STR.
Big Fat High BFH 1038 in mid Tasman Sea tonight 3 Oct is expected to
wander slowly along 40S this week easing to 1030 by the time it gets to
around 170W around Thu 7 Oct, and then slide around the south side of
the LOW that will be blocking its way. Yes there is a squash zone of
enhanced easterly trade winds on the north side of this High. It is, at
present, Sun 3 Oct in the North Tasman sea between 25 and 30S - and
should wander east with the high. It isn't a major, but has been near
gale force about the Whitsundays over past few days.

Next High is not expected to be as intense of the BFH but is likely to
wander east along 35S. It should bud off Australia into the Tasman Sea
around Sat 9 Oct and slide across the north of North island by Wed 13
Oct.

NZ AREA
Between the aforementioned Highs there is to be a passing trough, it
should cross the NZ area on Thu 7 Oct to Sun 10 Oct, preceded by NW
flow, accompanied by a series of fronts and followed by come cool SW
winds. This front is expected to have only minor impact at 30S so it
you are in Fiji or Tonga and wish to sail to NZ and can arrange a voyage
around the back end of the outgoing High, and rendezvous with the front
on 9 Oct near 30 to 35S, then that should be a reasonable voyage to NZ.

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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