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

11 April 2010

BOBGRAM7 issued 11 April 2010

Issued 11 April 2010
Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas are from
the patterned world of weather maps, so please fine-tune to your place.
Dates are in UTC unless otherwise stated.

Best latitude with west-going current is around 1 deg NORTH of the
equator... but it generally has light winds. There is occasionally a
zone of tropical showers near the equator from between 100W and 130W, so
take a latitude slightly further south for a useful sailing breeze that
generally has settled weather.
Intertropical convergence zone ITCZ is very active between 2 and 5N

South pacific convergence Zone SPCZ was last week indistinct and mainly
along 20S between southern Fiji and southern French Polynesia. There is
also a portion of SPCZ from North Queensland and across Papua New
Guinea/Solomons/and stretching to Kiribati/Tuvalu slowly building.

A low, left over from last week, Low 1, is located near 40S well to
south of Southern Cooks and is expected to travel east--- the tropical
section of the trough associated with this low - a zone of slack winds
and random squalls - is likely to cross Southern Cooks on Monday 12
April and stall over FP from 13 to 16 April.

A new low or trough, low 2,has developed on SPCZ to southeast of New
Caledonia and this system is expected to get captured by the trough
moving onto NZ, so that it should travel across eastern North Island on
Tuesday/Wednesday 13/14 April.

HIGH cell over Chathams has held some clean clear air over the North
Island over the weekend for a few days thanks to support from the upper
air. All this is changing now, and this High is expected to migrate
east along 40S this week and the get squeezed southeastwards around the
remains of Low 1.

Next High is over Aussie Bight and is a slow-moving system--- should
cross Bass Strait around Thu 15 April and then move northeast across the
Tasman and get squeezed so that it noses across northland around Sun
18-Mon 19 April

If you are about to head off north or east WAIT until the incoming
trough/front has gone - it is over Fiordland on Mon 12, very wet and
preceded by strong NW winds, then crossing rest of NZ 13-14 April. Also
WAIT for the cooler showery southwest flow that follows this front to
turn southerly over Northland and settle down - that makes Friday 16
April as best departure date this week.

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