Bob Blog 1 March 2020



Compiled Sun 01 March 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 January compared with the start of Feb may be seen at

Early February (below)



Late February (above)

The main changes are in the South Pacific Ocean, with the hot pool in the Tasman Sea relaxing.

According to BoM (Australia) the Indian Ocean Dipole IDO and ENSO and SAM are all neutral – so there are no major climate drivers active at present. That means that it is the short-term drivers (such as MJO) that we need to watch to work out weather changes in advance.

During February anomolies in the North Pacific have relaxed and there have also been some small changes in the pattern around South America.

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 January (below)



Average isobars for February (above)

The weather pattern hasn’t changed much, but for an intensification in the low in the north Pacific. One interesting feature is the rise to 1020+ for the Antarctic High. This may increase the SW winds in the mid-latitudes, perhaps.

Pressure Anomalies January (below)



Pressure Anomalies February (above)

There has been fair amount of change in the pressure anomolies since January, but higher than normal pressures remain over NZ area.

Zooming into the NZ area, and comparing monthly anomalies from last month with now, shows that the subtropical ridge STR has strengthened a little (as far as the 1015 isobar is concerned) but hasn’t shifted much. The 1010hpa isobar remains in much the same place.




February (above)


The Tropics

Latest cyclone activity report is from.

The TCFP tropical Cyclone Formation Potential at seems to have been discontinued.

We seem to be having a lull in activity at present.



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 stay much the same this week, from Tuvalu to Tokelau to Southern Cooks.

A sub-tropical low is expected to form south of Niue on Tuesday local then travel south along around 160W.


Accumulated rainfall for next week from (isobars are for Sunday night).

Subtropical ridge (STR)

HIGH near 45S 150W is expected to fade by Thursday local.

High just east of the North island tonight is expected to go SE and fade away by Tuesday.

New HIGH is expected to move into south Tasman Sea on local Tuesday, over southern NZ on Thursday and then east of the SI along 45S.

Tasman Sea /NZ/Aus

Trough over southern NZ on Mon fading over the North Island on Tues and Wed. local.

Low expected to move for interior of Aus to Tasmania on local Thurs an d then off to SE.

Associated trough is expected to stall over the South Island from Sat 7 March.

OK for Noumea to Australia.

As for sailing east across the Tasman: it may be possible south of 35S but avoid the troughs and their swells, and the passing High late in the week.

From Panama to Galapagos/Marquesas:

Northerly winds to around 4N this week, then light winds to 2N, then SE winds to Galapagos.

The ITCZ has a gap in it between 90W and 79W but does have outliers that reach as far south as Galapagos at times.

Winds are occasionally expected to be SE/S to north of Galapagos, so that’s an OK short cut to Marquesas this week, albeit showery and light winds at times.


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

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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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