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

05 February 2012

BOBGRAM issued 5 Feb 2012

Issued 05 February 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 in the atmosphere. The Southern Oscillation Index was 2.3 in late December, and eased to 1.01 during January and is down to 0.79 on 5th February.

A new MJO cycle of enhanced convection is making its way across Australia and the Coral Sea. Near equatorial NW/W winds have broken out across Solomons and are likely to spread towards 180 this week.

The South Pacific Convergence zone SPCZ was very intense last week across Papua New Guinea Vanuatu and Fiji --- this part of the zone had the MOST intense rain on the planet last week according to TRMM—it is less intense further to the southeast across Southern Cooks, and another convergence zone is sitting over French Polynesia. With a new MJO cycle approaching it is likely that we are now moving towards the "business part" of this cyclone season over the next few weeks.

TC JASMINE has formed in the western Coral Sea and is likely to go SE, maybe ESE and cross the Loyalty Island between New Caledonia and Vanuatu on Wed/Thu 8/9 Feb, and then turn south over the 11/12 Fe weekend and weaken.

Fiji Met Service is closely watching a LOW SSW of Fiji that has squally gales over the Tonga area. This system may develop further on Monday as it crosses southern Tonga and then should weaken as it moves off to the southeast.

The low that bothered New Caledonia lat week is still a feature on the weather map, but has lost most of its moisture--- its remains are found near Lord Howe Island at present, and should track southwards and a little eastward across the South Taman Sea over the next few days.

A slow-moving high is wandering gradually along 50S to east of NZ and should lose its gripping ridge over North Island from Thu 9 Feb… until Wednesday 8 Feb a moist northerly flow should affect much of NZ.

The next High should spend this week wandering along 40S across the Aussie Bight, with enhanced easterly winds on its northern side along the Aussie Coast. This High should make its way across the south Tasman Sea on the Sat/Sun 11/12 Feb weekend and then onto South Island by Tue 14 Feb.

Between the high pressures to the south and the low pressure to the north--- the Tasman Sea is likely to have mainly easterly winds from Thu 9 to Tue 14 Feb.

Also, these high pressures over NZ should keep other things away for a while.

The front that went over NZ mid-last-week was followed by a light SE flow, and this filled the NZ area with low cloud. Then that leftover low from New Caledonia made its way to near Lord Howe and combined with a little jetstream making its way around the upper ridge and produced a stream of high cloud that has been making its way across central NZ the last few days. The result has been a messy anticyclone for NZ's Waitangi Day weekend, with lots of cloud and also some damp areas -- some have called it a "filthy high", and it has been a classic illustration of one of my ten reasons for "hating a high".

There is a weak trough and southerly wind change over NZ between the two highs mentioned above… At this stage the timing for this is likely to be on Thu/Fri 9/10 Feb, but nothing dramatic is being indicated in this trough at this stage.

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