Bob Blog



Issued 31 January 2016

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.

During summer there are cycles of increased convection every 4 to 6 weeks or so that can trigger tropical cyclones. These are called Madden Julian Oscillations and the phase diagram of the MJO can be seen at


This phase diagram shows that the next cycle of increased convection for the South Pacific is likely to be around mid-February, but that it is also likely to be weaker than the MJO cycle we had at the turn of the year.

The meteorologists at Meteo France in New Caledonia are constructed a model that converts the behavior of MJO into a probability map for the formation of tropical cyclones, and it is no great surprise this model also is picking mid-February and the most likely timing for the net cyclone.



Tropical Cyclones

TC STAN formed during the past week over the seas to northwest of Australia and is now moving inland.


Weekly rain maps for the tropics over the past two weeks show a gradual strengthening of the South Pacific Convergence Zone, especially in the Coral Sea and along the Queensland coast.



Weekly rain signatures for past two weeks, as seen at



Weather Zones (see text) as expected mid-week on Wednesday (GFS model) showing wind, isobars, Sig wave height green lines, swell direction purple arrows, SPCZ and STR.

SPCZ=South Pacific Convergence zone.

The SPCZ is reforming mainly between equator and 10S, with tongues of convection onto northern Vanuatu and towards Samoa and Fiji.

STR= Sub-tropical Ridge

HIGH east of NZ on Monday is expected to move off to the east later this week.

New HIGH over Tasmanian at end of the week is expected to travel into mid Tasman early next week.

For NZ and Tasman Sea

Trough that is crossing New South Wales on Monday is expected to deepen into a low over mid Tasman sea by late Wednesday and then deepen further an it travels across northern NZ during long weekend of 6 to 8 Feb (Waitangi day public holiday has been Mondayised).


See my yotpak at for terms used.

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