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

02 July 2011

BOBGRAM7 issued 3 July 2011

WEATHERGRAM
YOTREPS
Issued 3 July 2011
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.

TROPICS
Southern Oscillation Index SOI remains in neutral territory, dropping from 0.29 on 26 June to 0.08 on 3 July.

Galapagos to Marquesas: The seas around Galapagos are slightly warmer than normal and the SSE winds there are slightly less than normal. It is making more sense to get west as soon as possible and seek the better winds west of 95W. So just one way point may be all that's needed now…somewhere near 6S 134W and then head for Marquesas. The current along this route is meant to be mostly west-going, but one yacht has reported an east-going head current near Marquesas.

South Pacific Convergence Zone SPCZ is active from northern Coral Sea (near Solomons) to the Fiji Area and then to the southeast where it merges with jet streams and the mid-latitude troughs. The troughs are forming a chain of lows between Northland and Tonga tonight, with associated gales and heavy rain, and these are expected to move southeast, fading over eastern North Island on Tuesday.

SUBTROPICAL RIDGE STR
The High that moved across NZ this weekend is expected to peel off to the east along 40S, reaching 120E by next sat 9 July with a zone of enhanced trade winds on its northern side as it travels.
The next high is expected to stay over central Australia until 12 July and then cross Tasman Sea maybe 15 to 20 July. SO this is a week of weak STR in the SW Pacific- typical of winter.


TASMAN SEA/NZ AREA
So what we have this week for Tasman Sea/NZ area is a disturbed westerly flow, strong to gale at times. This will set itself up after the Tuesday Low moves off eastern North Island, and may reach a peak over NZ in wind and cold (and mountain snow) on Thu 7 July, and then again on Sat 9 July, and Mon 11 July.
Heavy SW swell is likely in Tasman Sea from 6 to 12 July – avoid.

SAILING TO/FROM NORTHERN NZ.
Departing from Northland – wait until Tuesday for the winds to turn offshore, then brace for those swells.

The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com
Feedback to bobmcd@xtra.co.nz

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