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

31 December 2011

BOBGRAM issued 1Jan 2012

Issued 1 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 is steady and strong in the atmosphere. The Southern Oscillation Index SOI (30day running mean) was 2.26 on 25 Dec and on 31 Dec. It is likely to persist for the next few months, encouraging the South Pacific Convergence Zone SPCZ and subtropical ridge slightly pole-wards.

That MJO of enhanced convection mentioned last week moving across Australia is now weakening away. That means we may be in for a few quiet weeks in the tropics.

TC GRANT has also weakened away – There is a branch of the South pacific Convergence Zone SPCZ over the northern Coral Sea, with a weak extension towards New Caledonia---- a (new) small Tropical Low may form in this zone during the week, hovering west of Vanuatu for a few days and then broadening over New Caledonia on Thu 5 Jan. It may visit Fiji on Fri 6 Jan and then wander south along the dateline early next week.

The main branch of the SPCZ is still stretching from Tuvalu to Tokelau to Northern and Southern Cooks. As mentioned last week it has formed a tropical low, around 1005 near Southern Cooks. This system is not well placed for development and should move south then away to the southeast.

High has nosed across Tasmania and into SW Tasman Sea this weekend, and should move across North Island on Tuesday and Wednesday. Next High is expected to cross Tasmania on Friday 6Jan and spread around Southend of South Island on Sun 8 Jan, followed by a Northerly flow.

A transitional trough made for a wet end to 2011 in NZ, and thundery conditions for the interior North Island for New Year 2012. Some of the cold air left behind aloft from this trough may induce more inland showers for North Island on Monday afternoon.

After Wednesday's brief High, another transitional series of troughs are expected to bother mainly the South island on Thursday-Friday-Saturday 5-6-7 Jan with a few fronts.

Should be OK coming and going from Northland this week

Changing timezones:
Samoa and Tokelau have sacrificed Friday 30 Dec altogether so that they are now on the western side of the date line and can trade with Australia and NZ on the same days of the week. For those of you on the eastern side of the date line these old verses of Robbie Burns famous rhyme may still apply tonight:
We two have paddled in the stream,
from morning sun till dine ;
But seas between us broad have roared
since the days of auld lang syne.
For auld lang syne, my friend,
for auld lang syne,
we'll take a cup of kindness yet,
for the sake of auld lang syne.
And here's a hand my trusty friend
And give us a hand o' thine
And we'll take a right good-will draught,
for the sake of auld lang syne.

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