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

10 May 2015

Bob Blog

Issued 10 May 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.

For those thinking about landing at Tanna, Vanuatu:
The following notes have been sent to me by good-fella Eric Simmons from

1 Lenakel, on Tanna, isn't too bad as a Port of Entry, anchor in sand at
19 32.07S 169 15.91E, just behind the reef and you will have a comfortable
stay unless the wind moves to the South from Southeast and then it will be
rolly. Do not even try to use the concrete wharf!

2. It is possible to temporarily clear into Vanuatu at Port Resolution, SE
side of Tanna ,if you get advanced permission from Vanuatu Customs and
Inland Revenue, you need at least 24hours advanced noticed it can be two
months. This can be done on the "Contact Us" page of their website,

You will need to let them know the place that you wish to arrive at in
Vanuatu, e.g. Port Resolution, Tanna, an approximate date of arrival, name
and description of boat, who is on it and documentation plus anything that
you are carrying that may need declaring, so basically copy all the
information on your advanced arrival form that you have completed and paste
it into the email when you are requesting approval. The fine men at the
Customs Department will get back to you with approval in short time
providing nothing is untoward. Once you have this and you arrive at Port
Resolution, Werry at the Yacht Club will contact Customs and Immigration who
will travel over to inspect and clear you. There is a fee of 5000vatu for
Customs and 5000vatu for Biosecurity for clearing in a port other than a
Port of Entry. There is also a charge of 15000vatu for travelling for 2hours
over the horrendous road from Lenakel and 2 hours back again. Just remember
they will help you if you play by the rules but woe betide those who don't.

If you need to know anything about Vanuatu you can refer to www. where you can download a free cruising guide for
Vanuatu or email us on

The Atmosphere:
The Southern Oscillation Index SI sums up the weather pattern over the South
Pacific as one number and is based on the standardized difference in the
barometer readings between Tahiti and Darwin (30 day running mean).
It relaxed to zero in early March and then went negative, to be -10 units
for a few weeks in late March/early April, then relaxed in April and is now

If this index remains lower than -10 for four weeks in a row then we have a
fully- blown El Nino, but since it is now relaxing the trend is away from
an El Nino at present.

The Ocean
Last year at about this time, the Climate Prediction Center (CPC) predicted
a 70 percent chance of a weak to moderate El Niqo onset by last August, and
an 80 percent chance that it would occur by last November.
Well, we got a weak and stuttering El Nino instead.
The latest guidance from the CPC now indicates the current weak El Niqo
condition could strengthen to a moderate or even a strong event by mid or
late 2015.
In terms of Sea surface temperature: A weak El Niqo is classified as sea
surface temperatures in a selected area around the eastern equatorial
pacific (STEEP) for 3 consecutive months to be warmer than normal within a
0.5 to 1 degree Celsius range. A moderate El Niqo is classified as a 1 to
1.5 degree Celsius anomaly and a strong El Niqo is above 1.5 degrees

The latest CPC ensemble forecasts indicate that warmer than normal sea
surface temperature will continue through January 2016. Some of the model
solutions indicate as much as 2.5 degrees warmer than normal while the
consensus line indicates around 2 degrees.

Super typhoon NOUL is sideswiping the Philippines tonight. This is already
being followed by its successor DOLPHIN The equatorial westerly winds have
been very productive recently around Papua New Guinea.

The rain map for the last two weeks also show this build-up of activity. the
Solomons are in for a drenching this week, Weekly rain signatures for
week, is seen at \

Galapagos to Marquesas:
Best winds for departing are on local Thursday/Friday.
As last week the best strategy is as follows: First of all head for 5S 100W.
Then the middle leg is westwards along 5 to 6S as far as 125W enjoying a
west-ward going current. And then the third leg is to go direct in SE
winds. There now appears to be likely that a convergence zone may form
along 3 to 5S west of 125W next week.

SPCZ=South Pacific Convergence zone.
SPCZ is expected to remain active across Solomons and that LOW moves slowly
SW into the Coral Sea brining drenching rain and several squalls.
That LOW is likely to finally fade in the Coral Sea around early next week,
but from 20 May and new low may move slowly towards Vanuatu, so avoid
Solomons and the Coral Sea and keep on watching nearby.
Remainder of SPCZ spreads from Solomons to Tuvalu Samoa to Tahiti. This may
break into chunks during the week and a new zone may form across Southern
Cooks replacing the zone over Tahiti.

STR= Sub-tropical Ridge
STR is expected to remain north of NZ this week.
No Highs in Tasman Sea this week. Next big HIGH is expected to spread from
Australia into Tasman Sea from Sun 17 May (next week) and reach northern NZ
around Fri 22 May.

Departing from Northern NZ going north.
Trough is expected to cross NZ on Tuesday and another on Thursday followed
by a deepening Low on Friday/Saturday. The next likely looking weather
pattern for a possible departure north or northwest is Sat16/Sun 17/Mon 18th

Departing from Northern NZ going east.
The long period of roaring 4os weather that NZ is now about to experience
is good for this voyage, but you need to be careful and try and run the
northern edge of the roaring 40s zone, maybe at 44S at times.
Email me at for more info.

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