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

07 June 2008

BOBGRAM7 issued 8 June 2008

Issued 8 June 2008
Bob McDavitt's ideas for South Pacific sailing weather.
(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

NEWS: I'm now publishing the WEATHERGRAM at so if you want one by email send an
email to, no subject required, saying SEND

Galapagos to Marquesas: New suggested plan: because the winds are
mostly south-south-east around Galapagos to 105W use these to hop north
to the equator and sail westwards along the equator: Avoid the strong
east-going current between Equator and 3 degrees S. Near Equator 105 to
110W head SW - there is less current here - and from 5S 120W to
Marquesas to winds start to turn to be south-easterly.

The South Pacific Convergence Zone was rather quiet over the Coral Sea
recently, and is now slowly returning to that area. It has been more
active than normal over Fiji and in a broad band from there across Tonga
and Niue and parts of the Southern Cooks. This branch of the SPCZ is
forecast to wait for pressures to start falling between Vanuatu and
Fiji, as is likely to happen around Thu 12/Fri 13 June UTC. This
pressure fall is then likely to trigger a rapidly deepening LOW that
will move off to the SE - across the Kermadecs on Sat/Sun 14-15 June
UTC. There will be a squash zone between this low and the High to the
south--- strong enough to generate gale East /NE winds and heavy swells
for a time. Avoid this LOW and its squash zone.

The tropical extension of the trough associated with this low is likely
to reach Tonga on 15 June UTC / Niue on 16 June UTC / and fade over
Southern Cooks on 17-18-19 June UTC , preceded by a weak NE winds,
accompanied by tropical squall and followed by a return to trade winds.

Anyone sailing from French Polynesia westwards will need to sail through
that SPCZ.

Mid Latitudes
The Big Fat High BFH in the Tasman Sea is expected to cross the North
Island on Wednesday - with a squash zone of enhanced trade winds on its
northern side between 170 W and 170E mainly along 20S. When this BFH
moves off to the East on Thursday and Friday it is expected to induce a
fall of pressure on its northwest shoulder-that will be between Vanuatu
and Fiji, triggering the low mentioned above. Avoid this low.

So this BFH turns out to be NOT the best scenario for sailing from NZ to
Fiji or Tonga... but OK for sailing from NZ to New Caledonia or eastern
Australia. The trough following the BFH in the Tasman Sea on 11-12 June
is expected to fade away on 13 June. Not like that trough which brought
heavy rain to Queensland last week.

The terms used here are more fully explained in the METSERVICE Yacht
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