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

22 November 2015

Bob Blog 22 Nov



Issued 22 November 2015


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.


The ICA seminar week in Opua (and there was one in Newcastle too) went well.

Thanks to all those sailors that attended my seminar on Friday afternoon.

It was great to meet with you and get your feedback—some of the stories you told were priceless and worthy of writing up.


El Nino:

The weekly value of Nino3.4 was measured last week to reach 3.0 C (above normal)

As seen at

This is a record reading, but it is the monthly NINO3.4 reading that counts, and also there are other ways of measuring El Nino.

Perhaps the broadest parameter is the Multivariate ENSO index which uses both atmospheric and oceanic data, as seen at, is plateauing at 65.  It reached 66 in the 1997/98 and 1982/83 El Nino episodes.

The current El Nino episode is predicted to peak during the next three months and ease to neutral by mid-2016.


Tropical Cyclones:

Tropical cyclone features may be seen at Last week we had a set of twin tropical depressions near 170E.

The one in the southern hemisphere (93P)went west across northern Vanuatu and into the Coral Sea.

The one in the northern hemisphere (95W) also went west, taking it towards the Philippines – it now has the name In-Fa and is expected to re-curve and stay out at sea.

In the south Indian Ocean TC ANNABELLE is expected to travel south near 70E.

And in the warmer than normal seas off Mexico’s west coast tropical depression RICK is expected to travel north near 120W.

The Weekly rain maps show convection traveling southwards from the equator into the southern Indian Ocean and into the  South Pacific Ocean.

These can be seen at



SPCZ=South Pacific Convergence zone.

The main part of the SPCZ is strong in activity and extends from Solomon Islands to Samoa, with a dip south towards Fiji.

A tropical LOW is likely to form on this zone north of Fiji by mid-week and then travel across the Samoa/Northern Tonga region by end of the week, very likely bringing squally rain and possibly bring strong winds. This may be a hazardous feature so if you are in the area keep close tabs on its progress, and take adequate precautions in advance.


STR= Sub-tropical Ridge

The STR is very strong this week. A HIGH is expected to travel across northern NZ on Monday and then linger to east of North island for the remainder of November and into early December. Fronts crossing the Tasman Sea are likely to be diverted by this strong High so that they travel onto to the South Island.


Over NZ/Tasman:

Disturbed west to NW flow south of Northland with occasional fronts.


Travelling Tahiti to Marquesas.

Easterly winds are expected to turn and be from NE by end of this week, and maybe NW next week. Active convergence zone with squally showers is expected to lie in-between Tahiti and Marquesas by end of this week.


Between Tropics and NZ:

The HIGH lingering to east of North Island from this week into around mid- next-week gives a great opportunity for sailing to NZ from Tonga/Fiji/New Caledonia.


See my yotpak at for terms used.

See my website for information on tailor-made voyage forecasts– Feedback to Tell anyone you like that to subscribe they should email me.

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