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

23 July 2017

Bon blog for 23 July

Compiled Sun 23 July 2017

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.

Bravo to Lisa Blair for being the first woman to sail solo around Antarctica below 45 South (with one stop due to a dismasting). Lisa crossed her outgoing track on Friday 21 July at 9:48pm local time. Inspirational.
I have been emailing daily weather ideas to Lisa throughout this trip, but that's just idea- sharing and does not affect her claim to have sailed this adventure solo and unassisted (but for the stop at Cape Town for a new mast). Lisa has had knock downs, giant waves, winds over 80 knots, snow, hail, bumped into a container ship, encountered an easterly gale, and wallowed in large wind holes. Her blogs are at

If you feel inspired by this accomplishment, please buy one of her beanies to help out, while they are still available. See

This is the peak of the heat for the Northern summer, sometimes called 'the Dog Days' - named for the appearance just before dawn of Sirius, the Dog star and brightest star in the sky, from around 19 July. Sure enough, it's busy with cyclones as we can see from, showing 5 cyclones = Fernanda and Greg east of Hawaii, and Kolup, Noru and Roke between Hawaii and China.
Also 3 depressions and 3 "invest" areas. These storms are mostly oceanic, but Roke seems to be heading for Hong Kong, and the remains of a faded Fernanda may bring some rain to a dry Hawai'i, if they are lucky.

Last week's rain map, compared with the week before, shows a decrease in rain around the South Pacific, and an enhancement in the rain over India, SE Asia and Indonesia.
Rain for the past week may be seen at

SPCZ=South Pacific Convergence zone.
The SPCZ starts this week draped from Solomon Islands to Tuvalu and Tokelau Islands, and is having a weak week further east.
A passing trough, associated with a front in the Southern Ocean, is expected to go east across southern cooks on local Tuesday, and another may reach New Caledonia area on local Thursday and then move onto the Tongan area by local Sunday. These troughs are preceded by NE winds and followed by south or southeast winds.

Subtropical ridge (STR)
From Monday to Wednesday UTC a HIGH is expected to travel east across northern Tasman sea along 27S, and the further east to east of NZ along 30s from Thursday to Sunday UTC. There may be a squash zone of enhanced SE trade winds near 10 to 15S on the north side of this High.
From Friday to Monday UTC, another High is expected to travel east across northern Tasman sea along 30S.

Between NZ and the tropics:
Avoid the trough that is expected to be crossing northern NZ on Wed/Thu and early Friday.

French Polynesia to the west:
This looks to be a good week to go west. The SPCZ is still weak and expected to be confined to the Solomon Islands to Tokelau Islands area. However, there may be a squash zone of enhanced trade winds between Tahiti and Niue between Friday and Sunday local.
Also, a weak passing trough is expected to affect southern cooks on local Tuesday, and another may affect New Caledonia on local Thursday.
If you would like more detail for your voyage, then check to see what I offer.

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