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

23 March 2014

BOBGRAM issued 23 March 2014

WEATHERGRAM
YOTREPS
Issued 23 March 2014
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.
20 March at 16:57 UTC the sun seen from earth was directly overhead the
equator--- this was the equinox, and marked a significant turn in our annual
solar orbit.
ALSO Today, 23 March, marks WORLD METEOROLOGICAL DAY The theme this year is
Weather and Climate: engaging youth If you know any 8 to 12 year olds,
consider giving them a barometer for their next birthday. That seems to be
the most susceptible age for this sort of gift (teenagers tend to be so
easily bemused, and those 7 or younger tend to prefer toys rather than
instruments.
One thing that barometers give us is the SOI:
SOI The Southern Oscillation Index SOI sums up the weather pattern over the
South Pacific as one number. It is based on the standardized difference in
the barometer readings between Tahiti and Darwin.
SOI (30 day running mean) has dived negative in the past few weeks. After a
high late January/early February its 23 March reading was MINUS 1.29 units.
IF an El Nino cycle is approaching THEN this usually shows itself around or
soon after the equinox, so maybe this swing marks the beginning of a trend.

TROPICAL TOPICS
A pulse of extra tropical convection has been moving across the South
Pacific Coral Sea over the past few weeks-This is called a Madden Julian
oscillation or MJO and it triggered TC GILLIAN, HADI, LUSI, and, last week,
MIKE. The low that was once GILLIAN is still an entity and may redevelop as
it travels south into the Indian Ocean but should fade in a few days time.
This MJO cycle has now exhausted itself and the convection in the South
Pacific Convergence Zone SPCZ has been mostly removed. It is likely to take
a few weeks for the convection to rebuild, and by the time the next MJP
cycle arrives, it may be late April--- too late and too long after the
equinox for another cluster of tropical cyclones.
SO this is a good indication that TC MIKE (and GILLIAN) mark the swansong of
this Cyclone season.

Weather Zones
Panama to Galapagos: Winds become mainly light and variable between Panama
and Galapagos from tomorrow, also there is expected to be some convection
around Isla Mapelo reaching a peak on Wednesday UTC= Tuesday local. Also,
there is expected to be some convection around the Galapagos.
SO not the best this week.

SPCZ South Pacific Convergence Zone
This is weak at present and should slowly rebuild mainly between Solomons
and Fiji/Tonga. There is a zone left over-convection about Northern Cooks
and central French Polynesia, and another zone over Tuvalu/Tokelau. The zone
along 5S is still reveling in the overhead sun it has had in the past few
weeks and tends to get extra convection around the equinox because of this,
but the sun is now heading for 5N. The SPCZ branches are not expected to do
much. It looks like an OK week for Island hopping.

STR Sub-tropical Ridge
The STR is expected to maintain good strength between 45 and 35S with
ridge-tongues sticking out well from transient HIGH centres. There may be a
zone of enhanced SE winds on the north side of each of these HIGHS, found
half way between the H and the SPCZ a squash zone at 20S. On Wednesday one
of these may be between Noumea and central Queensland.
These squash zone travel EAST with the HIGH centre, even though they
comprise of SE trade winds.

New Zealand area
Remains of MIKE are throwing a 2-metre long-period swell onto NZ east coast
at present and for next few days, along with local light winds = wonderful
surfing.
On Tuesday, expect a Front and SW wind change.
Then a HIGH should cross Tasmania on Wednesday and travel slowly NE across
Tasman Sea and then over North Island on Friday/Sat Sunday
28/29/31 March. Enjoy.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is at metbob.wordpress.com, click FOLLOW at bottom
right to subscribe. Weathergram text only (and translator) is at
weathergram.blogspot.co.nz My website is at metbob.com - To unsubscribe,
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