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

28 March 2009

BOBGRAM7 issued 29 March 2009

Issued 29 MAR 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.

The "low from the Coral Sea" that was mentioned in last week's
Weathergram turned out to be JASPER which blossomed well last Tuesday
but then found the rising pressures over NZ were too much for it and did
a U turn and died.
I'd say that the New Caledonia highlands also had a hand in toppling
JASPER over; literally it was trapped between a rock and a high place.

The South pacific Convergence Zone SPCZ is still very active in the
Vanuatu area, with a LOW on Sunday near the Loyalty group/southern
Vanuatu. This Low should track off to the east-southeast, crossing the
Kermadecs/Minerva area on Tuesday and passing by 30S 160W, south of the
Southern Cooks, on Thursday. Avoid.

After Wednesday, the remains of the SPCZ in the Coral Sea will likely
travel northwards. It is likely to breed another tropical low near
Rotuma, to NW of Fiji Islands, and this may deepen a lot next weekend
and affect FIJI, Watch out for this.

There is a "twinning" of the Intertropical convergence zone (which lives
at around 3N) along around 7S all the way from 90 to 120W. This is an
equinoctial feature and should start to fade this week. Another branch
of the SPCZ from Tuvalu to Northern Cooks may last for a few weeks.

The HIGH that is currently zipping across the Aussie Bight like a
squeezes orange pip is well positioned, thanks to some fresh dense cold
air from the southern ocean, to intensify to a peak of over 1040 hPa in
the South Tasman Sea on Tuesday. This is exceptional, and will result
in an intense squash zone somewhere between northern NZ and
Kermadecs/Fiji/New Caledonia that will likely last until this High moves
off NZ on the 4/5 April weekend.

After Sunday's warm westerlies (27 in Dunedin at local 6pm today), the
forecast is for some frosty southern Ocean air (dropping to 5C Tuesday
night and almost single digit daytime highs on Wednesday). This cold
southerly isn't very wet but may trigger some hail on Monday. On
Tuesday it should reach the eastern North Island. On Wednesday, it may
bring some rain as an "easterly onset" to Auckland and Northland. The
HIGH that follows on Thursday and Friday will be an autumnal one with
light winds and maybe some morning fogs. The front that follows next
should bring a strong NW flow to southern NZ on the 4/5 April weekend.
Sunday 5 April will be 25 hours long as NZ changes from Daylight saving
to Standard time.

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