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

29 October 2017

Bob Blog 29 Oct 2017



Compiled Sun 29 October 2017

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.



Another good website for watching out for Tropical disturbances is

This site combines information from a number of websites dedicated to watching tropical disturbances.  When using it, remember that your insurance companies will mainly be interested in if you heed information that comes from the OFFICAL warning agencies, and in our part of the world that’s Fiji Met Service or NZ MetService (websites given in last weathergram) and, around Australia , the Bureau of Meteorology.

See  for the Coral Sea region.



TC PHILIPPE formed over Cuba in the past day or so and is now heading northeast where it is likely to follow the Gulf Stream.  This system may re-intensity into a mid-latitude system in a few days, thus have a stronger spin of wind around it and get deflected to the northwest and inland near New York.   If so it has the potential to deepen to 970hPa and bring a northwest gale to Lake Ontario. Reminds me of  Gordon Lightfoot’s ‘Wreck of the Edmund Fitzgerald “(in Lake Superior, 10 Nov 1975)) with lyrics: “When the gales of November come early” see

In the NW Pacific TC SAOLA is forming over Micronesia near Guam and is expected to travel NW then N towards Japan.


Looking at the weekly rain maps at from last week and the week before, we can see a burst of heavy rain in the past week around central America and Guam., and another near the central Pacific to the north of Hawaii.  Intensity seems to be easing around India, in the ITCZ across the North Pacific and in the SPCZ across the South Pacific.



SPCZ=South Pacific Convergence zone.

The SPCZ is expected to stay where it is, from Solomon Islands to northern Vanuatu to northern Fiji to between Samoa and northern Tonga to between Niue and Southern Cooks.  Any voyage from Tahiti to Tonga will need to sail/motor thru the SPCZ and it is likely to breed several squally showers this week.  Avoid.


Subtropical ridge (STR)

There is a Big Fat High (BFH) HIGH east of NZ from Monday to Thursday.  This is being supported by a break in the normal upper level Jet Stream pattern, and is indicated by the mid atmosphere (500hPa level) wind map showing the shape of the Greek Capital Letter Omega, but upside down in the Southern Hemisphere.

The left and right hooks of the OMEGA are associated with surface lows.  

So, this BFH is expected to BLOCK the troughs in the Tasman Sea this week and redirect them AROUND New Zealand rather than onto NZ.

For more about the Omega pattern see

And for a blocking index in the Southern hemisphere see

(This site doesn’t show this block yet as it is still forming.)


From Friday this block is expected to weaken, and the surface high should relax and move off to the northeast, allowing a new HIGH to travel east across Tasmania into the Tasman Sea from Saturday.


Between Tropics and NZ

There is a squash zone of strong east to NE winds between the BFH and the tropics.

Those departing from Fiji or New Caledonia to NZ should arrange their voyage so that they do not get near NZ until after Thursday.

This squash zone is expected to visit the Minerva/ South Tongan area from Tuesday to Thursday, so stay put for that. Should be able to depart Tonga or Minerva from Friday, but may need to try and time your departure taking into account south to southwest winds near NZ. 

The next trough to reach northern NZ is likely around 5 to 6 November. 


Between New Caledonia and Australia

Looks ok for departure Noumea any day this week.

The trough crossing Brisbane on Monday is expected to deepen into a low in central Tasman Sea by Tuesday, but the BFH should push that off to the south so it just fades away on the Noumea  to Brisbane route.

Next intense thundery trough is expected to reach Brisbane/Bundaberg area around late Mon 6 November or Tuesday7 November, so avoid that as arrival date.


“I can't control the wind but I can adjust the sail.”

― Ricky Skaggs


If you would like more detail for your voyage, then check to see what I offer.

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