Bob’s Blog 28 Aug

Issued 28 August 2016
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.

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) remains in neutral territory. Its 30-day running mean is in the 1 to 9 units area on this Australian scale.

SOI trend (x10) since 2013 showing us in neutral territory is seen at

The Ocean: The warmer the sea the quicker it evaporates, tossing water vapour into the air, where is rises and cools into cloud. The equatorial Pacific region hosts the widest and warmest sea on the planet. Thus its sea surface temperatures SST may be thought of as a factor in the running of planetary weather engine. When SST in the target zone (equatorial Pacific between dateline and Galapagos) are notably cooler than normal, this is called a La Nina episode.


Sea surface temperature anomaly as seen at shows that we now have cooling seas in the target area, and there MAY be a weak La Nina in the next few months

The Tropics
TC LIONROCK is in the NW Pacific, TC MADELINE may reach Hawaii next weekend, (LESTER, further east is fading) and TC GASTON is expected to turn around mid – Atlantic. There are also two possible tropical lows, labelled GENESIS in this map, which may affect eastern coast USA this week.
Cyclone tracks may be seen on


Rain activity is generally weakening except for a few spots in the Indian Ocean and around Japan.

Rain for the past fortnight from



SPCZ=South Pacific Convergence zone.
SPCZ this week is expected to slowly develop from Solomon Islands to north of Fiji area.


HIGH is expected to travel east slowly across the Tasman Sea and then across to east of  NZ on Father’s Day weekends (3 to 4 September).

There is expected to be a weak squash zone of enhanced easterly winds on the north side of this HIGH between sat 3 and Mon 5 Sep .

May as well watch this HIGH for departure/arrival.


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