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

11 October 2009

BOBGRAM7 issued 11 Oct 2009

WEATHERGRAM
YOTREPS
Issued 11 October 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.

Vanuatu Quake--- this was a sideways shake so didn't toss the sea around
too much. Phew.

Palolo (or Balolo in Fiji): These worms rise out of the coral reefs for
a spawn-fest in the waning moon of Oct and Nov (around now), that's if
they haven't been upset by recent events. Anyway ask the locals,
something to do while waiting for a good voyage south,

Northwest pacific cyclone season - because the names used tin that
region cover several language with different scripts they don't go
alphabetically in the English alphabet after all. Thanks to those who
picked me up on my surprise at the jump from KETSANA to PARMAR/MELOR
last week.

MELOR was a real super cyclone for a while and managed to mostly miss
Guam, then smashed into south-eastern Japan, killing 5 and injuring
around 100.

In the South Pacific the Convergence Zone SPCZ has split into two, with
one branch from around Solomons to near Fiji, and another branch from
Tokelau across Northern cooks and touching between central French
Polynesia and Marquesas-a rare northeastern position for the SPCZ.

I think the western branch will move onto Tonga around mid week, and a
Low may form between Tonga and Niue on 14 Oct then move southeast and
deepen as it feeds off an upper jet stream. SO that may keep yachts in
Tonga while yet.

There has been an equatorial westerly during the last week between
Solomons and Micronesia, and GFS model is trying to produce a Low over
the Solomons area out of this later this week... but EC model doesn't.
In this case I'm inclined to agree with the EC.

Winds in the northern Coral Sea were strong last week but should relax
over next few days as a trough crosses the Tasman. They are likely to
get strong again
For 17 to 24 Oct as another High crosses the Tasman and this strong wind
zone is likely to affect New Caledonia from 18 to 22 or 23 Oct, so see
if that times in with your plans around there.


TONGA to NZ/ CROSSING THE SUBTROPICS
As said before- a weak part of SPCZ should visit south Tonga around
12-13 Oct and a low may form on this near Niue on 14 Oct. If you are
already at Minerva you may miss this, or perhaps can see it overhead
tonight.

In tandem with this, the HIGH over Tasman Sea today already pokes a
tongue of ridge towards NE of North Island and should travel east along
this axis maintaining a reasonable subtropical ridge between Tonga and
NZ, at 30S anyway, until 17 Oct. Although this is a nice enough ridge
to sail across the subtropics with, the problem is timing - it will get
you to NZ just when the next big trough arrives, frontal zone around 17
oct followed by a couple of days of SW to S winds. Either avoid or work
out a coping path.

BTW this trough is likely to breed a 988 Low over Tasmania in Tuesday,
avoid. Its first front should cross NZ on Wed 14 Oct and may be
somewhat thundery, announcing the return to spring over NZ after 3
winter-like lows.

Next HIGH from Australian bight should cross New South Wales on 17-18
Oct and Tasman on 19-21 Oct. So there is a possible window: a yacht
capable of up to 6 knots could possibly depart Vavau around 14 Oct, go
thru the "17Oct NZ front" in a weakened state at 25S on 19Oct and then
have SE winds on the beam for the rest of the trip to NZ -between low
near south of Niue and High in Tasman Sea, reaching Opua in light winds.
But this scenario may well change so you'd need an update before
departing.


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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