Bob Blog 3 Feb



Compiled Sun 03 Feb 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.

Late January brought some extreme weather, with the peak of a heatwave over Australia, some spots in NZ having a heatwave, an unpresented polar vortex over North America, and the continuing drenching monsoonal low over norther Queensland. A mighty meal for any meteorologist. Sadly, I was out of action, as I needed emergency surgery for a blocked gut.   I’m back home now, so here’s my regular blog once more.


Sea Surface temperature anomalies as at end of January may be seen at


The eastern equatorial Pacific around Galapagos is the focal region for ENSO and the warm area there seems now to be shrinking. There is also a corridor of warmer-than-normal conditions between Samoa and Southern Cooks — this may add oomph to the South Pacific Convergence zone and act as a possible path for cyclones. The Tasman Sea remains warmer than normal, and ready to add extra rain to any passing lows. And the Southern Ocean is showing a lot of melt water, which is cooler than normal.

The Gulf Stream off the east coast of North America still stands out, which is unusual at this time of the year.

To see how the annual weather cycle and the seasons are working out, check the average isobar maps from

Average isobars for past 30 days and their anomaly:



The subtropical ridge in the southern hemisphere is almost at its southern most latitude and the anomalies show it is stronger than normal and maybe somewhat further south than normal.

Zooming into the NZ area, and comparing January with November (December data missing due USA govt shutdown) shows that to north of NZ, the 1010hP (between light blue and dark blue) isobar has shifted south from around 10S to 20S. to south of NZ, the 1010 remains in much the same spot, but the pressure gradient shows stronger westerly wind sin the Southern Ocean in January than in November.


JANUARY      image

The last 30 days of rainfall, and its anomaly are seen at


This shows that during January, western South Pacific and Tasman Sea has been dry and it has been French Polynesia that has had the main share of the South Pacific Convergence Zone.


Latest cyclone activity as at and TCFP tropical Cyclone Formation Potential as seen at


There is a monsoonal low north of Mt. Isa, and this is expected to stay over land next few days, limiting its chances to develop to a tropical cyclone.

There is a convectively active phase of the MJO over the Western Pacific at present, and it is expected to weaken this week. It may remain in the western Pacific and intensify again by mid-February.


In the OLR (outgoing longwave radiation) prognosis from , blue zones are likely to be cloudy areas.


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


SPCZ=South Pacific Convergence zone.

The SPCZ is like a monsoonal trough stretching from Australia to Fiji and then as a convergence zone from around Samoa to Tahiti. Tropical lows are likely to form and space themselves along this trough line.


Accumulated rainfall for next week from CZ= convergence zone.

Subtropical ridge (STR)

HIGH to east of central NZ on Monday expected to travel off to the east-NE.

New High is expected to travel east across the south Tasman Sea on Tuesday and then around eastern NZ on Thursday and after that to the east-NE.

Australia/Tasman Sea / New Zealand

With the Highs crossing the southern Tasman Sea, the main wind flow north of latitude 35South is from the east, good for sailing from New Caledonia to Queensland.

Easterly winds are expected to get strong and seas rough near Northland from Wednesday in a squash zone with rising pressures to the south and falling pressures to the north.

Further south there are expected to be swinging winds from a passing front on Monday and Tuesday, and increasing NW wind from Friday to Sunday.

Panama to Marquesas

Looks OK to go any day this week with northerly winds for starters and a good tail current to current to 2N 85W. From there either peel off to the Galapagos Islands or follow the current along around 1deg north to 125W and then head for Marquesas Islands.


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