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

09 March 2014

Bob's Blog

Issued 09 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 Tahiti and Darwin.
SOI (30 day running mean) has dived negative in the past few weeks. After a
high late January/early February its 8 March reading was MINUS 0.75 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.
Kiwi-born Kevin Trenberth, a senior scientist at the National Centre for
Atmospheric Research, agrees that an El Nino is brewing: see http://www.

"This could be a substantial event and I think we're due," Trenberth said.
"And I think it could have major consequences."

A pulse of extra tropical convection is now moving from northern Australia
into the Coral Sea.
This is called a Madden Julian oscillation or MJO and it seems clear to me
that is episode of tropical activity is going to be the last, or swansong,
of this Cyclone season.
HOWEVER it may trigger several cyclones over the next few weeks.
The first has already formed in the Gulf of Carpentaria and is called
( as seen at
Another tropical Low in the Coral Sea is on the verge of becoming a cyclone
as seen at It seems to be
about to go further northeast/offshore.
And a third tropical system over Vanuatu is very likely to develop into a
tropical cyclone between Vanuatu and Fiji by Tuesday (next name on their
list is LUSI). This system should then travel south or southeast, but is
somewhat at the whim of the weather feature around it so MIGHT REACH
NORTHERN NEW ZEALAND ON SAT 15 MARCH. Those making plans for that day
should check on the progress of this system and take it into

Panama to Galapagos: I am aware that some are almost ready and looking at
this leg, waiting for the occasional burst of NE winds that is good for this
voyage. Well, indications are that the wins between Panama and Galapagos
are likely to be light and variable this week, and mainly head winds. Might
be better to delay departureand might be OK next week.
Stay tuned.
I advise those thinking about this route to check http://earth.nullschool.
net and see the ocean currents (click earth, mode=ocean, earth) and prepare
accordingly. Notice that the surface current is WITH you, even if the wind

SPCZ= South Pacific Convergence Zone
Apart from the cyclonic activity in the Coral Sea and around Vanuatu, the
SPCZ is active mainly between Samoa and between Southern Cooks and French
Polynesia this week.

STR= Sub-tropical Ridge
The STR is expected to maintain good strength around 40S across Tasman Sea
(Wellington should continue to enjoy good weather the NZ Festival), and
around 35S in SE Pacific.

New Zealand area= a mixed bag
Slow-moving HIGH across central NZ from Monday to Thursday. Then the next
HIGH should sideswipe Southern NZ on Friday to Sunday with light winds.
However, IF that tropical system now near Vanuatu does come south THEN
Northern NZ is in for strong winds and heavy rain on Sat 15 March--- the
Ides of March ( so this needs

See my yotpak at for terms used.
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