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

14 June 2015

Bob's Blog



Issued 14 June 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 Atmosphere:

The Southern Oscillation Index SOI 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).  The weekly update has been lower than -10 for four weeks and now is relaxing.

 SOI is shown at



TC CARLOS is following the lead of BLANCO onto the Mexican west coast.

 The Indian Monsoon arrived in Kolkata/Calcutta on Thursday with a bang—a thunderstorm

  This can be seen at

And in the South Pacific the Highs have been HIGHER than normal,  with a 1038 hPa HIGH visiting New South Wales for much of the last few days:

The Sydney Barometer for past week, may be  seen at

The rain map for the last two weeks shows BLANCA and CARLOS off the west Mexican coast, and also a burst of intensity over Solomons, and a build-up in intensity along the South Pacific Convergence zone. The weekly rain signature may be  seen at



  Galapagos to Marquesas:

Best winds for departing are on local Sunday/Monday/Tuesday. There is still signs of a good west-going current along around 6S from 115 W to 125W.


SPCZ=South Pacific Convergence zone.

SPCZ has been strong over the Solomons and is building in intensity from Solomons to Samoa and then to the southeast. A trough is expected to cross Samoa/Tonga by Wednesday UTC and then move onto Tahiti by Sat 20 UTC, followed by a squash zone.


STR= Sub-tropical Ridge

STR is along its normal latitudes for this time of the year.  The HIGH that has been intense over New South Wales over last few days is expected to weaken as it skirts around northern NZ on Wednesday, with a squash zone of enhanced trade winds on its northern side along 20S,  and then re-intensify to over 1030hPa as it travels east along 30/35S to east of NZ. 

Next HIGH is expected to travel east across Tasmania on Sat 20 June.


Tasman Sea /NZ area:

Disturbed SW flow on Monday easing on Tuesday and a High is expected to skirt northern NZ on Wednesday.  LOW is expected to deepen off New South Wales by Wednesday 17 June and then travel SE across southern NZ by Friday, with associated front moving across Tasman Sea and onto Northern NZ by Saturday, preceded by strong to gale northerly winds on Friday.

Low may deepen between NZ and Fiji early next week on 22/23 June.


Departing from Australia to the tropics this week:

There may be some good weather for departing after the LOW, perhaps on Friday 19 June.


Departing from Northern NZ going north.

OK to depart with Monday’s SW winds, but that will give a rough start.   The light winds on Tuesday and Wednesday get replaced by northerly winds on Thursday, strong to gale on Friday and then a passing front on Saturday, followed by a southerly/SE flow.

If a low does form between Northland and Fiji on Mon/Tue 22/23 June then it is likely to be worth avoiding.


See my yotpak at for terms used.

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