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

21 March 2010

BOBGRAM7 issued 22 March 2010

Issued 22 Mar 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.

I am a day later than usual this week, since I spend 9 hours driving
back to Auckland yesterday and decided to rest in the evening.

Now that TOMAS and ULUI have taken away most of the convective energy
build-up in the South Pacific, it looks as though' we may be in for a
reasonable quiet period now. The South pacific Convergence Zone SPCZ
today stretches from Vanuatu to Fiji/Southern Tonga to south end of
Southern Cooks. This zone is expected to drift north and weaken this
week. Also, the forecast is for a build-up of convection in the central
Coral Sea, and maybe a low or a trough of light winds near New Caledonia
around this weekend from Friday 26 to Sunday 28 March.

We had the equinox last Sunday, and as the sun is now overhead in the
Northern Hemisphere, it is interesting that a tropical depression has
developed in the NW Pacific. This is expected to weaken to east of
Philippines by Friday 27 March.

HIGH cell is forecast to cross the Southern Bight on 23 March (World
Meteorological day) and then cross the Tasman Sea/Northland area on 25
to 27 March keeping the rain away. There will be an enhanced zone of
trade winds along 25S. This zone will extend eastwards all the way to
the date line as the High cell moves east. More fetch for more swell
for the Brissy coast.

The next HIGH cell is likely to take a more southern route, crossing
Tasmania on Friday 26 March and then the South Island on Sunday 28
March, producing a squash zone of onshore easterly winds onto the
southern North Island. Avoid.

Deep Southern ocean Low wandered close to Fiordland earlier today so
that its front was intense with 75 knot gusts and well over 100mm rain
on the Southern Alps. The wind helped delay the cricket in Wellington.
Front will weaken as it crosses the rest of NZ on Tuesday.

Another deep Southern Ocean Low is likely to wander north close to Otago
on Thursday. Its front should cross NZ on Wednesday preceded by strong
NW winds and heavy alpine rain and followed by an unsettled westerly

Then, on Friday we are forecasting the front that will lead in a HIGH
cell. It, too, will likely be heralded by intense Northwest wind and
rain over south end of NZ, but this time it will be followed by
southerlies and clearing weather - and not as cold as the last one
(which gave many inland areas a frosty start to 18 March last week).

The terms used are more fully explained in the METSERVICE Yacht Pack.
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