Bob Blog 04 Aug 2019



Compiled Sun 04 August 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 start of August may be seen at


The main pattern changes are the ribbon of cooler than normal sea around the Galapagos. There is also a return to near normal in the Tasman Sea and a return to near normal off western Australia (an easing of the Positive Indian Dipole

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



The subtropical ridge is much the same as last month. The monsoonal trough has deepened and shifted north over Asia.

Zooming into the NZ area, and comparing monthly anomalies for end of last month with now, shows that the subtropical ridge STR is slightly north of where it was last month. The anomalous trough over NZ is closer to the mainland than last month,

JUNE clip_image009

JULY clip_image011



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

It’s been a busy week in the Pacific and still is with ERICK, FLOSSIE and now GIL travelling west towards Hawaii. Also FRANCISCO near Japan.

There are areas of potential development in the China Sea, near Bangla Desh, and now also in the Atlantic. The Cyclone Season is heating up.




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 stay over Solomons and stretch across norther Vanuatu o the Fiji /Samoa area.

Passing trough over the Gambier Islands on local Sunday/Monday 1014hPa.


Accumulated rainfall for next week from

Subtropical ridge (STR)

SAM went negative last week as expected allowing the cool air of the Southern Ocean to spread into the Tasman Sea/ NZ area with big swells. As a precursor for this the STR went north of NZ. The next High is now in the Tasman Sea and is expected to travel NE on Monday and then along 25 to 30s, being NE of NZ on Wednesday.

A weaker ridge is expected to travel across south Tasman on Thu and the South Island (only) on Friday.

Tasman Sea /NZ/Aus

Disturbed westerlies for western NZ pretty much for the whole week, but easing winds on Tuesday/Wednesday offer an opportunity for voyages to Tonga and maybe Fiji. However, it looks to be a no-go week from NZ to Australia.

Looks Ok for Noumea to South Port early this week, but not Ok after around Thursday.

Tahiti to Tonga

Looks good to go this week with trade winds.


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

Leave a comment

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.