Bob Blog 25 July

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.

Compiled Sunday 25 July 2021

Regarding last week’s blog, with its checklist for handling a squall, it has been suggested that the mnemonic for remembering it be replaced with the word PRICK (rather than APRICOT), dropping the A (Anticipate) and O (Over), and replacing the T for Thunder with K. Rather rude but more memorable.

Also, this week I would like to share with you a link to a COMPRENDIUM OF WEATHER INFORMATION FOR FRENCH POLYNESIA ( as prepared by David Vogel and available with a host of other information at This is a must read for yachts visiting French Polynesia and useful for those planning to get from there westwards across the South Pacific.



The latest cyclone activity report is at and Tropical Cyclone Potential is from


In-Fa is making landfall onto China. Cyclone NEPARTAK is heading towards Japan, and expected to weaken (a little) on Tuesday

So, the outlook is for wet and windy conditions mid-week for the Tokyo Olympics.



Weather Zones Mid-week GFS model showing isobars, winds, waves(magenta), Rain (Blue),

STR (Subtropical Ridge), SPCZ (South Pacific Convergence Zone) and CAPE (in pink)


CAPE mid-week as seen by ECMWF and GFS from


SPCZ=South Pacific Convergence zone.

The SPCZ is expected to be about average stretching from Solomon Islands to Fiji/Tonga, and a convergence zone s expected near Samoa occasionally over Southern Cooks and Tahiti area.


Rain Accumulation next five days from


1 Active trough is crossing NZ tonight and on Monday followed by squally west to southwest flow until Tuesday. Avoid.

2 LOW traveling east along 30S south of Southern Cooks early this week bringing light winds to French Polynesia FP.

3 HIGH 1020+in Northern Tasman Sea by Tuesday expected to travel east along 30S and reach south of FP by end of the week. Good trade winds with this High.

4 Active trough in Tasman Sea by Thursday. LOW 995 expected to form in this trough over northern NZ on local Friday and then travel east along 30S until early next week bringing westerly winds as far north as Samoa. Good for getting east but wait until early Aug if going west from FP.


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