Bob McDavitt's ideas for sailing weather around the South pacific

24 January 2016

Bob Blog



Issued 24 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.


This El Nino cycle seems to now be relaxing. The monthly NINO 3.4 index which measure the amount of heat stored in the eastern equatorial Pacific Ocean reached a maximum of +3.0 in December--- slighter more than the previous strong El Nino in 1997/98, and is now relaxing. Maybe this heat is being released into the atmosphere activating  weather systems around the world.

NINO 3.4 index may be  seen at


In spite of the easing of NINO3.4, the weekly SOI index has become more intense over the past two weeks:

SOI index may be seen at


Tropical Cyclones

TC VICTOR moved under the Jetstream and lost its top and has be downgraded to a tropical low. Soon it will leave the tropics and may unwind a little more at it travels south to the  east of North Island.

When it encounters colder and denser air near 40S on Thursday it may deepen again for a day or so.


Tropical Storm CORENTIN is the only tropical cyclone around this evening and is in the Indian Ocean.


Weekly rain maps for the tropics, as seen at ,

over the past two weeks show a weakening of the South Pacific Convergence Zone, and a build-up of activity in the Indian Ocean.



SPCZ=South Pacific Convergence zone.

Most of the old SPCZ has been taken south by VICTOR, but a new one is reforming mainly between equator and 10S. The equatorial westerly winds

that were around last week have all gone now.


STR= Sub-tropical Ridge

STR is strong near 40S to east of NZ, with a quasi-stationary High near 160W. The remains of VICTOR are being directed southwards around the

western side of this High.

The next HIGH is expected to travel along 50Sacrosss the South Tasman Sea on Tuesday and around the south end of the South Island on Wednesday and

Thursday, delaying the southward progress of the remains of VICTOR.


For NZ and Tasman Sea

Unsettled. On Monday a low is expected to cross the South Island, and a lingering trough should move onto the North Island on Tuesday. On

Wednesday and Thursday the low that was once VICTOR may regenerate as it travels south off the east coast of North Island and central NZ  And from

Friday an E/NE flow is likely over the country as the new HIGH builds east of the South Island.


See my yotpak at for terms used.

See my website for information on tailor-made voyage forecasts

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