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

05 July 2008

BOBGRAM7 issued 6 July 2008

Issued 6 July 2008 NZST
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

Galapagos to Marquesas: For the late comers: Head direct for 4S 96E
then go straight. This will avoid the strong east-going current and use
the winds best: winds are SE over Galapagos and turn easterly to west of
110E. Be on watch for a few tropic squalls between 120W and Marquesas

The South Pacific Convergence Zone is going thru a quiet time now. It
starts the weak active along a zone from Papua New Guinea across
Solomons and northern Vanuatu to Fiji and Niue and to the southeast.
The section east of the dateline is expected to be active on Mon UTC and
then fade away from Tuesday UTC. There is another branch of the SPCZ
near10S from Tokelau to Marquesas. This is more properly known as a
shear line. It has lighter easterlies to its north and strong easterlies
to its south, anyway it is breeding thunderstorms so be wary there.

A mid latitude low is expected to deepen in the cold air that is being
shunted into the subtropics--- near 33S 155W on Thu or Fri UTC. This
will activate the SPCZ between Tahiti and Southern Cooks into a trough
with squally showers.


HIGH above 1028 crossing the central Tasman Sea along 40S next few days
and NZ on Wed 9 July UTC will enhance the trade winds to north of it
into a squash zone. This Squash zone should cross New Caledonia on 7-8
July and over Fiji-Tonga-Niue from 9 to 13 July UTC. Take care.

A cold pool moved onto the North Island this weekend in tandem with a
deepening surface low off the east coast- bringing the coldest day of
the winter so far on Saturday, with snow and ice closing many roads.
It'll be a hard winter storm to beat, perhaps this winter's nadir.

Weather window is ripe early this week for heading from NZ to Fiji/Tonga
and for coming the other way as well.

One last southerly wind change with showers rippling along NZ east coast
on Monday, then a few days with light winds- frosty morning and sunny
day- from a passing HIGH.

Next front /trough should form off the Australian Coast on Tue 8 July
UTC and reach the South Island on Friday 11 July UTC preceded by NW
winds - good rain for the hydro lakes- then the North Island on Sat 12
July UTC followed by a westerly flow.

The next front, due over the North Island on 14 July may have strong
wind and rain, and will be followed by SW winds. This one is worth
avoiding; one of the computer models is developing a LOW with it.

NOTE: I am on leave from 9 to 15 July, so next weathergram may be
delayed a while and I'll be unable to do any voyage forecasts during
that time.

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