BOBGRAM issued 22 Jan 2012

WEATHERGRAM
YOTREPS
Issued 22 January 2012
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.

La Nina's indicators continue to relax after that late December high. The Southern Oscillation Index was 2.3 in late December, 1.36 on 14 Jan, and 1.16 on 21 Jan,

A new MJO cycle of enhanced convection is appearing in the Indian Ocean and is expected to arrive over western Australian later this week, increasing their risk of tropical cyclone formation. To help these there is a zone of near equatorial westerly winds across Indonesia which is likely to make its way across Papua New Guinea this week.

The South Pacific Convergence zone SPCZ is slowly reforming in the Coral Sea after a few quiet weeks there. It spent last week in a rather scattered fashion mainly along the date line between Tuvalu and Fiji and also across Tokelau then southeastwards to French Polynesia.
A low has formed within the SPCZ to south of Fiji near Minerva and this should wander off to the southeast--- it is likely to encounter some of the cold southerly air that washed over NZ today, this should take place between 30 and 40S near 160W on Tuesday and help form a deepening low that will move off to the south.
There is a risk that another low may form southeast of Fiji on Sat 28 Jan and do a re-enactment of this – moving south and deepening along 170 to 175W next week.

SUBTROPICAL RIDGE STR
A new large High is set to wander slowly south across the Tasman Sea along 40S and fade over North Island on Wed/Thu 25/26 Jan – this is a little to north of the track of the previous high.

The next high is expected to move more quickly than the current high taking the track along 40S across Tasman Sea and Central NZ on Friday 27 to Mon 30 Jan, good timing for Auckland's anniversary day long weekend and regatta.

TASMAN SEA/NZ AREA
Inbetween those two highs there is a transition time for NZ. A cold front fresh from the southern ocean is likely to reach southern NZ late on Thu 26 Jan, and sweep across South then North Islands on Friday and Saturday 27 and 28 Jan. It is associated with a deep southern low which is also likely to bring some heavy swell to southern NZ on Sun/Mon 29/30 Jan.

The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com
Feedback to home: bobmcd@xtra.co.nz, work: bob.mcdavitt@metservice.com