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

26 June 2010

BOBGRAM7 issued 27 June 2010

WEATHERGRAM
YOTREPS
Issued 27 June 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.

Galapagos to Marquesas: trade winds are now strong enough so that boats
faster than 6kt may sail this route directly, hugging 4S as long as
possible. Slower boats and those looking for an alternative route
should get to may between 1 deg and 2deg North of the equator for a free
ride on the equatorial west-going current, especially from 095 to 125W.
No weather to mention, but note that in the Northern hemisphere near
the Americas Cyclone CELIA is still going and Cyclone Darby is about as
well.

TROPICS
South Pacific Convergence zone SPCZ is active along 8 to 10S across the
Solomons area to Tuvalu and Tokelau, and then active again across French
Polynesia. There are occasional bursts of activity occurring about
northern Vanuatu and northern Fiji, but nothing organised.
Due to High pressures that are now blocked over southern Australia there
is a zone of enhanced trade winds in the Western Coral Sea and around
the north end of Queensland. This should ease after 30 June.

SUBTROPICAL RIDGE: STR
Large HIGH over 1030hpa to south of southern cooks / at 160W / is moving
steadily east along 40S. Its associated squash zone of enhanced trade
winds should affect southern parts of French Polynesia this week.

Small HIGH around 1020hPa is moving along 25S and should get from south
of New Caledonia today to south of Niue tomorrow/28 June. Another small
High around 1020hPa is likely between 25 and 30S to south of New
Caledonia on 29 to 30 June , and should then fade.

And the next HIGH is likely to bring a period of light winds across the
central Tasman Sea and NZ building to 1030+ from 5 to 7 July next
week...- a window that motor vessels may use to help cross the ditch as
comfortably as possible (and sailing vessels may wish to avoid).

TASMAN/NZ
This week in the local region we have just two small cells in the STR
around 25/30S, so the whole Taman Sea/NZ /east of the dateline area is
open to having a broad trough.
There should be one front/trough crossing NZ on Monday/Tuesday 28/29
June, followed by a disturbed W/SW flow for the remainder of the week.
After this SW wind change gets to Northland on wed 30 June, there should
be a reasonable window from sailing away from Northland. BUT note that
the frontal trough may deepen into a small low when it is north of NZ
and as it crosses near the Kermadecs on 2-3-4 June-so if heading for
Tonga ensure you go clockwise around it.

These conditions will make sailing TO New Zealand challenging this week.


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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