Bob Blog 11 April

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.

Compiled Sunday 11 April

Here comes the MJO again.

The MJO is a pulse of extra energy that travels around the tropics, mainly from the Indian Ocean to the Pacific Ocean. It takes around a week or so to pass each place and visits maybe once every 6 or so weeks. This coming week it is going to travel across the Pacific Ocean, and may trigger some interesting weather.

It can be seen best by looking at the MJO index 5-day running mean as seen by the CPC Climate Prediction Centre at

This shows we have had five MJO cycles since last October (blue tracks) and the current cycle is the quickest.


Another way of looking at the MJO is to use the Outgoing Longwave Radiation (OLR) as a proxy. The blue lane in this diagram shows low OLR due thicker than normal cloudiness.


The Tropics

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

There is also Tropical Cyclone SEROJA in the SE Indian Ocean which is forecast to make landfall over Western Australia on Monday. And there are some zones of moderate to high potential risk for the formation of a tropical cyclone in the western Pacific thanks to the passing of the MJO this week. Just a reminder that the cyclone season in the Southern Hemisphere nominally lasts until the end of April.



Weather Zones Mid-week GFS model showing isobars, winds, waves(magenta), Rain (Blue), STR (Subtropical Ridge), and SPCZ (South Pacific Convergence Zone).


Predict wind CAPE mid-week gives two possibilities for SPCZ.


SPCZ=South Pacific Convergence zone.

There is expected to be one branch of the SPCZ in the northern Coral Sea this week, then, in spite of the passing MJO, there is a gap around Fiji, and then another branch between Samoa and French Polynesia s.

Low that passed over New Caledonia last night is expected to zip southeast past the NE of NZ on Monday.

Passing trough on the SPCZ is expected to visit between Aitutaki and Tahiti on local Monday/Tuesday, followed by SW winds for the remainder of the week. Avoid.


Rain Accumulation next five days from

Subtropical ridge (STR)

High is expected to travel along 30S into the central Tasman Sea on Tue/Wed/Thu then linger rover northern NZ until the weekend. This offers a reasonable voyage between NZ and the tropics, or from Noumea to Australia this week, but NO GOOD for getting from Australia to Noumea.

Aussie/Tasman/NZ troughs

Low developing in south Tasman Sea on Monday is caught on the western side of its upper trough, and thus expected to travel northeast on Tuesday bringing with it some large swells. It should fade over the North Island on Wednesday, followed over Thursday and Friday by a westerly flow south of 37S.

Panama to Galapagos/Marquesas

Light winds around Panama, otherwise moderate south to southwest winds between 5N and Galapagos.

Taking the current into account, it looks better to get to Marquesas via south of Galapagos this week.


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