Bob Blog 14 June

Compiled Sun 27 May 2020

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 May can be seen at

Early June (below)


Looking at the SST during the past few months we see a continuing warm pool in the Indian Ocean/Tasman Sea/Fiji. This means there may be a NEGATIVE Indian Ocean Dipole is possible later this year over Australia with above-average winter/spring rainfall over parts of Southern Australia, perhaps—only 4 out of 6 models say a sort of yes.

According to BoM (Australia) ENSO (El Nino/southern Oscillation) is neutral but if there is further cooling along the eastern equatorial Pacific in the next few weeks the a La Nina watch may be triggered. SAM (Southern Annular Mode) is currently positive for a few weeks., keeping southerly outbreaks away.

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 isobars for past few weks of May (below)


May pressure anomolies (below)


Last month There was a belt of low pressure near 40-50S from south of South Africa to the east of NZ. It now covers much of the southern Ocean. The subtropical ridge is looking strong and lingering around 35-4=50 South, somewhat south of normal.

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the subtropical ridge STR has strengthened

Two months ago Below



LAST month (above)

The 1010 and 1015 lines have shifted south , a new1020 isobar has appeared , letting in only small doses of rain on to the North Island.

The Tropics

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

Tropical storm NURI is affecting the China Sea

There are a few small low to moderate patches of potential development but these are not really expected to come to much. But be aware.



Weather Zones (see text) as expected Wednesday 00UTC showing isobars, winds, waves(magenta), Rain (Blue), CAPE (pink), STR, and SPCZ.)


SPCZ=South Pacific Convergence zone.

The SPCZ is active around Solomon Island, over northern Vanuatu, and Tuvalu/Tokelau the stretched east loosely across French Polynesia.


Accumulated rainfall for next week from

Subtropical ridge (STR)

HIGH 1034 to 1032 is expected east of North Island on Monday and to travel off to ESE rest of week.

Next High 1036 Wed in SW Tasman Sea on Wed to travel NE and fade in central Tasma Sea 1026 by Saturday.

Next High 1038 hPa should appear in south Tasman Sea by end of week.

Tasman Sea /NZ/Aus

Between the first and second High a Trough should reach South Island on Monday Troughs over Southern South Island on Monday/Tuesday and North island on Wednesday followed by a southerly flow over NZ on Thursday and a low deepening east of the North Island on Friday.

From Panama: Not good this week, SW winds or light winds in Panama, and the ITCZ is visiting at times. It is most active/squally to 5N.


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