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

28 March 2010

BOBGRAM issued 28 March 2010

Issued 28 Mar 2010
Bob McDavitt's ideas for sailing around the South Pacific.
Corrected edition
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.

GALAPAGOS TO MARQUESAS Welcome to those of the new Puddle jump crowd
contemplating this voyage. Nothing much to report at this stage, all
looks quiet. Best east going current seems to be along around 30
minutes North latitude, but this may change.

It is looking to be another settled week in the tropical South West
Pacific. The next convective phase of the Madden Julian Oscillation is
not expected here until first or second week of April. There is some
bubbling activity over Northern Australia and Tropical depression
TWENTY-TWO is in the western side of Gulf of Carpentaria. Models differ
as its likely path, and currently it is most likely to go SW inland in a
few days. If it looks as though it may earn a name and make land fall
in southwest of the Gulf over Easter. If this system goes offshore and
towards the middle of the Gulf it will feed-and-grow on the warm seas,
and earn a name a cyclone. Even so it is then likely to make land fall
late in the week over southwest of the Gulf and then it'll starve and
die quickly.

South Pacific Convergence zone is still going through its re-build after
the cyclones of mid -March. It is currently mainly along 20S, feeding
off the subtropical Jetstream, with occasional burst further north (one
of these bursts is crossing Vanua Levu today/Sunday). Also there is
another zone building between 10 and 17S from around Northern Cooks to
French Polynesia. A trough is likely to develop on the SPCZ between New
Caledonia and Fiji around 31 march ad this should intensity into a LOW
as it moves south just west of the date line from Thu 1 April to do a
loop and end up east of the North Island on Mon 5 April ---
There's lots of convection in the Intertropical Convergence zone just
north of the Equator across most of the Pacific, and extending towards
the equator at times around Tarawa.

Next development to watch is a likely LOW developing in the North Coral
Sea. Models differ, and this area isn't really expected to bubble up
until after Easter, but it is worth watching this week.

HIGH cell is moving to east of the South Island tonight is expected to
build to over 1040hPa over Chathams on Monday. This high has brought a
wave of warm air from Australia to New Zealand and this warmth should
hang around all week.

Next HIGH , suitably shaped like an Easter Egg, is expected to cross
Aussie high around 1 April, to be south of Tasmania on 2-4 April, and
then may stall over NZ and gradually shift from Southland to Northland
from 5 to 8 April These highs are shepherding the lows around them ,
keeping rain away (from where it is wanted). This pattern is expected
to change during April.

Between the Highs there are some mediocre fronts this week. One is
likely to be attached to a LOW moving southeast over Southland on
Tuesday and Wednesday, preceded by a strong NW flow. This front should
stall and fade over central NZ on Thursday /Friday.

Another cold front, the herald of the Easter egg High, is likely from
southern ocean onto South Island on Friday and North Island on Saturday
- where it gets absorbed into the circulation of the LOW coming from
the north. Sometimes this can be a recipe for rapid intensification,
but this time it seems that the North Island mountains may block the
cold air that follows this front from circulating into the Low's moist
heart--- some heavy rain for eastern North Island, but not the full
works this time.

So, with fronts over NZ, an outgoing High, and a Low coming in to
northeast, it is Easter (south) easterlies for the traditional Auckland
to Tauranga Yacht race, and a spirited offshore wind to start the SOLO
TRANS-TASMAN CHALLENGE 2010 New Plymouth to Mooloolaba on Easter Sunday.
In New Zealand we are celebrating Easter this year with a 25 hour day
(it coincides with turning the clock back from NZDT to NZST).

May the Easter message bring all humans joy and a sense of purpose.

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