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

18 May 2014

BobBlog 18/19 May 2014

Issued 18/19 May 2014
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.

Apologies for late posting today; I was delivering a weather seminar and it
took a while to clear my inbox this evening.
First: A plea for your help,
I have an adventurer kayaker who is raising funds for the ASTHMA foundation
by paddling the Tasman, Australia to NZ. Scott Donaldson had to stop at Lord
Howe this week (see photo) to replace his desalination equipment, and is now
on his way again. I think if we all donate $2 via (click: donate any amount icon) then
this will boost his spirits tremendously. He has already achieved a record
as being the only human who has, so far as we know, kayaked from Australia
to Lord Howe Island!
You can learn more about his exploits at:
Judge for yourself if he has earned a $2 donation. (cheaper than the cost of
a cuppa, but if you all do it then thats $1000 to ASTHMA).

SOI. The Southern Oscillation Index SOI sums up the weather pattern over the
South Pacific as one number. It is based on the standardized difference in
the barometer readings between Tahiti and Darwin.
SOI (30 day running mean) has switched from pink to blue recently and is now
near zero

Still in the strange inter-seasonal zone with no cyclones around. Last week
looked normal.

Galapagos to Marquesas
No problems with any convergence zones. To get the best benefit of the
available current go for 3:30S 98W then 6S124W then direct to Marquesas.

SPCZ= South Pacific Convergence Zone
Once the Low that is tonight over Tonga goes off to the SE/SSE over the next
few days, the SPCZ is only likely to be noticeable from Papua New Guinea to
Samoa. By next weekend we likely to have just trade winds across the South

STR= Sub-tropical Ridge
The STR is north of its normal position for this time of the year, possibly
a hint that we may be moving into an El Nino. It is also reasonably strong,
with High cells expected to make it across northern NZ on Tuesday/Wednesday,
and along 30S to north of NZ on Fri/Sat 23/24 May.

My reporters tell me that there are 26 Yachts at Minerva tonight. I wonder
what the record is.
They have had strong winds since Saturday afternoon, and been on anchor
watch all last night, but no dragging. There is a squash zone between the
High in the Tasman and the Low over Tonga --- this was referred to in my
last weeks weathergram with an AVOID. It was 30 gust 40 knots there last
night, still 25 gust 35 knots today and tonight. Forecast is for wind to
ease on Monday but may take till Thursday for waves to ease back to the
average of 2 metres.
This squash zone is covered by a gale warning in the SUBTROPIC area covered
by MetService.

Departing from NZ to the tropics
Light winds over northern NZ on Monday/Tuesday with passing HIGH, Disturbed
westerly flow is spreading northwards this week and should reach northern NZ
with a passing front on Wednesday. Another front over northern NZ on
Saturday night/Sunday, preceded by strengthening NW winds.

See my yotpak at for terms used.
Weathergram text only (and translator) is at
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