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

27 May 2012

BOBGRAM issued 27 May 2012

WEATHERGRAM
YOTREPS
Issued 27 May 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 Southern Oscillation Index or SOI has relaxed to near zero. Its 30 day running mean started May at -1.1 but went to plus 0.5 in mid-May and was -0,14 on 27 May.

Indian Monsoon was running slightly ahead of the normal schedule but is now on its normal schedule.

In the South Pacific, the Convergence Zone SPCZ is now active between 4 and 10S from 133E all the way to 173W. It then spirals into a new low deepening near 18S 165W or between Niue and Southern Cooks. This Low should continue to deepen as it moves south-south-eastwards into the mid- latitudes. The SPCZ that is left behind in this process is expected to stay in much the same place this week. Another Low may form on the SPCZ in the Coral Sea around Sunday 3 June and move SSE into the Tasman Sea early next week. This should provide an interesting challenge to this year's Auckland to New Caledonia Yacht race starting this Queen's Birthday Weekend (NZ Holiday).

Galapagos to Marquesas: A continuation of last week and all clear of squally showers. Depart quickly SSW from Galapagos until 3S then WSW to 5S then west to 125W then direct.

SUBTROPICAL RIDGE STR
High that is south of French Polynesia at 40S should wander slowly east.
High in the Australian Bight should cross the Tasmanian area on Thursday and South Island on Sat 2 June, then Northern NZ on Sunday 3 June and then peel off to the NE of NZ on Monday 4 June.
Between these Highs the STR is very weak and Lows are allowed to play.

NZ /Tasman Sea troughs
A trough is moving across NZ tonight and should stall long enough to east of North Island to allow a Low to form there on Monday. This Low is expected to dance and play in the area NE of North Island on Monday to Wednesday and then move off to the east on Thursday and Friday. A front from the Southern Ocean is expected to cross the South Island on Thursday and bring a dose of southerlies and heavy swell to eastern North Island.

Departing from NZ for the tropics:
Wind flow over northern NZ for most of the week is likely to be from the south and southeast, but it may be strong at times with large swells because of the Low. This can be considered to be spirited by some and uncomfortable by others. These conditions are expected to weaken by the time the Auckland to New Caledonian Yacht race commences.

The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com and http://www.metbob.com
Feedback to bob@metbob.com

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