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

04 January 2009

BOBGRAM7 issued 4 Jan 2009

WEATHERGRAM
YOTREPS
Issued 4 JAN 2009  
Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas come from the patterned world of weather maps, so please fine-tune to your place. Dates are in UTC unless otherwise stated.
Welcome all to 2009 --- we are entering this year with a trend away from Neutral territory and towards a weak LA NINA.

TROPICS
TC BILLY went west off NW Australia, briefly grew to hurricane force and then faded.
The EC model is picking that another TC may form in the Gulf of Carpentaria this week, reaching a peak as it makes landfall going west early next week.
The South Pacific Convergence Zone SPCZ stretches from the northern Coral Sea to northern Vanuatu to the Rotuma area. There are now some squally westerly winds on its northern side between Solomons and Tuvalu.
 A MJO, or pulse of extra activity, is wandering east across the Coral Sea area this week, and this may help form low centres on the SPCZ. 
There is already one showing to northwest of New Caledonia. Computer models are coming up with different scenarios for the lows between the Coral Sea and Norfolk Island area.  Isobars around these lows will squash closer together in a zone to the south (in the easterly winds) and another zone to north and east (in the northwesterly winds along the SPCZ).
Any lows that do form are likely to head for the area between New Caledonia and Norfolk Island.
Another branch stretches between northern cooks and southern French Polynesia.  This zone is likely to move southwards this week, with lows possibly forming on it over southern Tonga heading for the Kermadecs and another near the Southern Cooks.  It is a good week to stay ashore.
SUBTROPICAL RIDGE
Eastern flank of the HIGH over the NZ area is expected to move off to the east enhancing the trade winds along 30S between 180 and 140W.  The western flank is expected to stall to west of NZ and fade away on Thursday.
TASMAN SEA/NZ
The front that crossed NZ on Saturday was preceded by a north to northwest flow that brought rain to the north and hot dry conditions to the east.  The southerly that followed was egged on by rising pressures of the HIGH.  It arrived in Canterbury at the right time of day to produce squally hail.
 The next front that will be followed on by an accompanying HIGH is expected to cross the Tasman on Thursday or Friday and reach the South Island on Friday or Saturday.  Models are divided as to whether this front does a repeat of the last front or stalls maybe around central NZ.
Its track is somewhat dependant on the behaviour of the Low that will then be near Norfolk Island.
 There will be a trough connecting these two systems and that will complicate things.  
Those intending to cross the Tasman Sea should keep checking updates.
The terms used are more fully explained in the METSERVICE Yacht Pack.
            More info at http://weathergram.blogspot.com
              Feedback to bob.mcdavitt@metservice.com

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