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

23 December 2012

BOBGRAM issued 23 Dec 2012

WEATHERGRAM
YOTREPS
Issued 23 Dec 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.
The Ocean. Along the Pacific equator, Sea Surface temperatures SST have recently been near normal with some below-normal SST near Galapagos- this situation is considered to support ENSO neutral conditions and computer models are picking this to continue into 2013. There is a zone with SST around 1 or more above normal from Samoa to Tahiti and another off NW Australia—these can possibly encourage the formation of the South Pacific Convergence zone SPCZ during the next few months and bears close watching.

The Atmosphere: Things are changing. The Southern Oscillation Index or SOI (30 day running mean) was hugging the plus 0.5 value since the beginning of September, but during December the 30-day average has dropped to minus 1, and this is in response to lower than normal isobars over Tahiti, so it is a definite shift towards an El Nino-like episode. Interesting.
EVAN is out of the tropics and gradually unwinding like a wind-up Christmas kids toy. It has not been able to encounter a Jetstream or cold front from the southern ocean so is not going to re-intensify like SANDY did. It is going west-wards across northern NZ and is expected to be picked up there by upper NW wins and taken southeastwards across central NZ on Boxing Day. A good blog on the future track of EVAN can be found at http://blog.metservice.com/2012/12/christmas-weather-daily-update/

Next week?
At this stage GFS model is picking that another tropical low may deepen into a cyclone between Solomons and Vanuatu by Friday 28 Dec and then go SSE to cross New Caledonia area on Mon 31 Dec/Tue 01 Jan. EC model is not so certain as to the intensity of this system yet but agrees with the timing. If you intend to sail in this area then keep checking for updates, and maybe delay. The next name on the list for South Pacific Cyclone is FREDA.

Sydney/Hobart Race –The teams are getting ready for a great race – check out http://rolexsydneyhobart.com/ Weather forecast is for a dream start then NE winds then a westerly or SW change on Dec 28th. If the super maxi can get to Hobart before the westerly they may have a chance of beating the race record of one day, 18 hours, 40 minutes and 10 seconds, set by the then 98 foot super maxi, Wild Oats XI, in 2005.
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See my yotpak at http://www.boatbooks.co.nz/weather.html for terms used.
Weathergram with graphics is http://metbob.wordpress.com/2012/11/04/weathergram-4/
Weathergram text only http://weathergram.blogspot.co.nz
Website http://www.metbob.com
Feedback to bob@metbob.com

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