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

13 February 2010

BOBGRAM7 issued 14 Feb 2010

WEATHERGRAM
YOTREPS
Issued 14 Feb 2010
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.

RENE seems to have maybe done a loop just east of Ta'u in eastern
American Samoa last night, and is now Cat 3 and may get to Cat 4
(170kph) ... heading for Ha'apai on local Monday morning and then may
travel across western side of Tongatapu Monday evening/night ... the
accompanying dangerous quadrant and storm surge will be o its
south-eastern side, so Nukualofa is in for a real battering. Brace.

RENE is likely to wander SW for a while longer but unravel as it leaves
the tropics and encounters cooler waters. There is a trough heading
east across the Tasman Sea ... it should cross New Zealand on
Wednesday/Thursday and pick up the remains of RENE and conduct them off
to the southeast on Friday and Saturday.

By then much of the rain will be east and south of its centre, so it
looks as though this rain may miss Northland (where it would be
welcome). However if RENE gets to travel a little faster than forecast
then maybe some of this rain will reach Northland. It's a race between
trough and RENE.

That trough spent last week delivering lots of welcome rain to the
interior of Australia as a low in the heat trough. the low is deepening
rapidly tonight of New South Wales as it encounters the EAC (East
Australian Current). The Low should weaken as it crosses the Tasman Sea
on Monday and Tuesday, fading back into a trough when it reaches the
South Island on Wednesday.

This Low seems to have missed out on the injection of cold air that I
mentioned last week - it has a protective ridge on its south-side.
However that ridge will have gone east of NZ by Wednesday and that's
when the new High is expected to be approaching Tasmania, throwing a
fresh dose of SW winds from the Southern Ocean ahead of itself--- if
this cold SW wind can get any where near the remnants of RENE then there
will be fireworks. At this stage this timing is against such an event,
and the High is expected to intervene and reach the North island by
Saturday ... maybe there will be an encounter well east of the North
Island on Friday/Saturday-maybe not.

Talking about fireworks: the South Pacific Convergence Zone SPCZ
remains very active along 5 to 10S across the South Pacific, especially
between Tokelau and Northern Cooks. Computers are picking a further
development in the area northeast of Samoa being born between Thursday
18 Feb and Tue 23 Feb (models are still differing on timing). The next
name on the Cyclone list is SARAH. Current output indicates this system
may move south sort of midway between Niue and Aitutaki/ Rarotonga -
however there is still plenty of time for it to take another path. Be
Aware.

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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