BOBGRAM issued 6 Jan 2013

WEATHERGRAM

YOTREPS

Issued 6 Jan 2013

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 Atmosphere: Things are changing. The Southern Oscillation Index or SOI (30 day running mean) was hugging the plus 0.5 value in Sep Oct Nov, but during the last few weeks has dived to almost minus 1. An interesting swing towards an El Nino.

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During the past week FREDA faded away over New Caledonia, and has turned into a mid-latitude low that has deepened a little just east of NZ during today and should weaken again as it moves off to the SE on Monday.

Australia is having a heat wave. The Monsoonal trough is expected to form a tropical cyclone over the sea west of Darwin on Monday and this system is likely to spend the remainder of the week travelling counter clockwise along Australia's west coast. A heat low may form somewhere over the interior and the pressure difference between the lows and the High over the Aussie Bight are likely to make for some strong hot winds reaching their pick over South Australia/Victoria from Mon 14 to Wed 16 Jan.

The South Pacific Convergence Zone SPCZ is now reforming in its normal summer position from Solomons to Fiji /Tonga with another convergence zone over French Polynesia. The next tropical LOW that is expected to form on the SPCZ is likely to do so near Minerva to South of Tonga around Sat/Sun 12/13 Jan.

STR Subtropical ridge

There is a STR high at 40S in the Aussie Bight. This is expected to move NE across the Tasman Sea on Monday/Tuesday 7/8 Jan and then weaken into a tongue-shaped ridge as it travels eastwards to north of NZ on Wed 9 Jan and then go SE and expand into a High again near 40S 160W by Thursday 10 Jan. Another High is expected to reach Aussie Bight from Tue 8 Jan and fade over Bass Strait on Thursday 10 Jan. Another high is expected to form near 45S in Aussie Bight on Sat 12 Jan and travel east to South Island on Tue/wed 15/16 Jan. All these highs have strong winds on their northern side.

TASMAN SEA/NZ TROUGHS

Trough moves off to east of NZ on Monday.

Front is expected to move onto South Island on Wed 9 Jan preceded by strong NW winds, hot in the east and wet in the west. This should be followed by strong westerly flow over much of NZ on Thu 10 Jan. Another front is expected over South Island on Sat12 Jan preceded by strong NW flow. This front is likely to be cross NZ on Sat/Sun followed by a southerly flow by Monday 14.

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NEWS: Jeanne Socrates in NEREIDA (Neptune's daughter) is about to round Cape Horn. She is doing a solo-non-stop unassisted circumnavigation, and I am helping (on the side) by watching the weather with her. There are lows ahead of and behind her so check out and see how things turn out.

To learn more about her story visit http://www.svnereida.com/ and if you are impressed then please click on the link to Marie Curie Cancer care and leave a donation at http://www.justgiving.com/jeannesocrates.

More News: I have been awarded in the New Year's Honour List-as a member of NZ order of merit for services to meteorology and yachting.
http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10856717

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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

Weathergram text only http://weathergram.blogspot.co.nz

Website http://www.metbob.com

Feedback to bob@metbob.com