Bob's blog, issued 16 March 2014

WEATHERGRAM
YOTREPS
Issued 16 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.

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 Tahaiti and Darwin.
SOI (30 day running mean) has dived negative in the past few weeks. After a
high late January/early February its 16 March reading was MINUS 0.86 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 is now moving across the South Pacific
Coral Sea.
This is called a Madden Julian oscillation or MJO and it has already
triggered TC GILLIAN, HADI and LUSI.
The low that was once GILLIAN is still an entity and may redevelop as it
travels west along around 10S out of the Gulf of Carpentaria.
This MJO cycle may trigger a few more cyclones this week and then fade out
and be the last, or swansong, of this Cyclone season.

WEATHER ZONES
Panama to Galapagos: There is an episode of useful NE winds for departing
from Panama to Galapagos between now and Tuesday local, and then the winds
become mostly light and variable again.

SPCZ= South Pacific Convergence Zone
There is a zone of convection across the Coral Sea along about 15S from the
Aussie coast to Fiji and a small tropical low may form on this branch but is
not expected to come to much.
The main branch of the SPCZ this week stretches from Samoa to the Southern
Cooks.. The GFS model is picking that Low may develop near Suwarrow around
Monday UTC (Tuesday local) and then deepen as it travels south to southeast
across the Southern Cooks. However not all models are picking this scenario,
so it is only a possibility at this stage.

STR= Sub-tropical Ridge
The STR is expected to maintain good strength around 40S across much of the
SW Pacific.

New Zealand area.
LUSI brought some useful rain, but farmers would have liked more.
A cold front is set to cross the South Island late on Monday (local) and
another front should cross the South Island.
For much of the remainder of the week NZ has light winds under a weak High
pressure system.

See my yotpak at boatbooks.co.nz/weather.html for terms used.
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