Issued 25 September 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.
Northern Hemisphere is still at peak cyclone season, with HILARY west of
The tropical ocean temperatures in mid pacific continue to be near normal, however there are signs of a growing pool of cooler-than-normal sea near Galapagos---so much that it has exceeded USA's Climate prediction centre CPC's threshold and they have called it a new La Nina. It is sort of neutral with bursts of La Nina at times.
From the atmosphere, the Southern Oscillation Index SOI is positive and increasing: its 30day running mean was 0.44 in 17 Sep and 0.75 on 21 Sep. Some lingering La Nina weather patterns persist in the atmosphere, and the Subtropical ridge STR in the Australia/Tasman Sea area is now being taken south of its normal position.
The South Pacific Convergence Zone SPCZ is persisting from Solomons to
SUBTROPICAL RIDGE STR
The STR seems to be south of its norm position of around 25S. That High near 40S in the
A large area of heavy SW swell associated with a low from the southern ocean is expected to reach NZ south coast by Wed 28 Sep and then move into the eastern flank of the High in early Oct – so avoid the centre of this high as it will have the combination of light winds and heavy swells – no good even for a power boat.
TASMAN SEA/NZ AREA
There is a developing Low between
After that high crosses central an northern
Looking further ahead a Low from the southern ocean is likely to reach Southland by Sunday 2 Oct, turning the flow over NZ to a squally westerly, then from Mon 3 to Wed 5 Oct next week, this low may deepen east of NZ, bringing a polar chilled southerly outbreak to NZ eastern coastlines. Avoid.
If you are planning to sail from Tonga/Fiji./Vanuatu/
On Mon 3 Oct to Wed 5 Oct a polar chilled flow hits Northland with W then SW then S winds, so don't plan on departing this week unless you are quick enough to reach Northland by end of Sun 2 Oct – and if you come south from New Caledonia, then also watch the progress of that low wandering along 30S.
The terms used are more fully explained in the METSERVICE Yacht Pack.
More info at http://weathergram.blogspot.com
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