Bob Blog 6 Oct 2019



Compiled Sun 6 October 2019

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.


Sea Surface temperature anomalies as at end of August and start of October may be seen at

late August (below)



Early October (above)

The peak heat of the northern summer/autumn has gone now and sea temperatures are relaxing and easing towards normal, but still slightly above,

In the Southern hemisphere there’s a large zone of cooler sea off the west of South America, and temperatures between Queensland and Northern NZ, and a return to normal temperature off the west of Australia.

To see how the annual weather cycle and the seasons are working out, we can check the average isobar maps for past 30 days and their anomaly from

Average August 2019 (below)



Average September 2019 (above)

Anomalies   August 2019 (below)




Anomalies September 2019 (above)

The southern subtropical ridge is much the same as last month. It is much stronger off to west of South American, and slightly stronger in the Tasman sea. . The monsoonal trough is a little further east and weaker.

Zooming into the NZ area, and comparing monthly anomalies for end of last month with now, shows that the subtropical ridge STR is in much the same place but slightly stronger than a month ago. There is still a SW flow over NZ, but it’s weaker than it was.

AUGUST … clip_image012

SEPTEMBER clip_image013




The latest cyclone activity report is at and TCFP tropical Cyclone Formation Potential at

At present there is one active cyclone HAGISIS off Japan and expected to skim along Japan East coast.

Looks like we are having a lull in the cyclone season.



Weather Zones (see text) as expected Wednesday 00UTC showing isobars, winds, waves(magenta) STR, and SPCZ. Pink area = lightning likely (high CAPE)


SPCZ=South Pacific Convergence zone.

The SPCZ is expected to visit Fiji on Monday and the Tonga /Minerva area on Tuesday, then return north to Solomons to Tokelau stretch from Solomon Islands to Tuvalu /Tokelau, similar to last week.

Weak upper trough 1012 over Tahiti on Wednesday with showers.


Accumulated rainfall for next week from

Subtropical ridge (STR)

The STR has retreated to 30S around NZ

HIGH to NE of NZ on Monday stalling and extending south near 170W/south of Southern Cooks on Tuesday to Thursday

Next HIGH is in Southern Ocean and expected to travel east along 50S to south of NZ on weekend 12/13Oct. 6,

Tasman Sea /NZ/Aus

Intense Low deepening in central Tasman Sea on Tuesday/Wednesday and crossing South Island on Thursday. Another trough/Low crossing northern NZ on Friday

Maybe another Low in northern Tasman Sea / Northern NZ early next week, not sure yet.

As for tropics to NZ this week, wait until Wednesday or latter for departure. Avoid arriving early next week (possible low)

For Noumea to Aus or vice versa: complicated thus week by passing trough.

Tahiti to Tonga

The passing upper trough 1016hpa+ hPa may bring some showers.

Trade winds expected this week, a good week to go west.


If you would like more detail for your voyage, then check to see what I offer.

Or Facebook at /

Weathergram with graphics is at (subscribe/unsubscribe at bottom).

Weathergram archive (with translator) is at

Contact is or txt 6427 7762212


Published by metbob

Pattern and Chaos

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