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Weather Forecasting: A Private Cruising Boat Perspective

By James Ellingford — last modified May 16, 2015 09:48 AM
An interesting and useful article by James Ellingford on weather forecasting for a Pacific Ocean crossing.

Published: 2015-05-15 23:00:00
Topics: Weather
Countries: Fiji , Samoa

Weather Forecasting: A Private Cruising Boat Perspective

Photo of MetBob ()Bob McDavitt)

Now, some may or may not know this but for this world trip I plan to use the services of a number of forecasting companies and I am currently using the services of weather guru to the stars, Mr Bob McDavitt or MetBob as he is known to millions!  What Bob doesn’t know about weather is not worth knowing.  Bob is used by many a sailor to cross the Pacific which is his patch in the world and one that he knows like the back of his hand.

Bob McDavitt is a New Zealander and has been a full time meteorologist since 1975 forecasting for marine, aviation and the general media in New Zealand and in Fiji.  Some may not know but in 1998 he was awarded the "Henry Hill Award" for his enthusiastic approach to sharing ideas about the weather.  Bob is a veteran of two campaigns for the America's Cup (in Perth and San Diego), and has helped Swashbucklers break records crossing the Tasman Sea and circumnavigating NZ, Earth Race and Jessica Watson in her circumnavigation of the world.  Nowadays he is in semi-retirement and continues to talk with weather users and help sailors cruising around the South Pacific travel safely.

Below, for those interested, I have inserted a copy, verbatim, of an email received on the 12th May where I have asked Bob for his long range thoughts about weather for our trip from Fiji to Samoa.

BOBs REPLY – “James, I agree with going next to Apia, Samoa. We can only attempt to do this when the trade winds relax, as they do occasionally, such as when we hopped from Vanuatu to Fiji.  There are two possibilities in the next two weeks (neither are as good as our last trip, but then again, C’est la vie.

Option 1 is next Monday 18th May

Forecast winds that may be encountered along this trip are given by the red arrows ,, one barb=10 knots and half a barb= 5 knots

Weather Forecast chart 1

Option 2 Departure Sat 23rd May:

Weather Forecast chart 2

Background small arrows are surface current (not much). Grid of larger arrows shows coloured wind barbs. Blue/green shading is rain. 2 and 3 green lines are boundaries of 2 and 3 significant metre wave height. 1012 line is an isobar”.

Once a date starts firming up then I receive a daily weather update from Bob with the following information:  Below is an example from when we left Vanuatu.

“James, I have been watching the squalls on satellite and see that they visited Tanna and Aneityum this afternoon but sort of sideswiped and missed Vila. They have left behind some cloud that should mostly clear Friday morning.

Probably better to leave early Friday rather than late Friday so that you get the best of the period of light winds. On Saturday these trade winds return, a head wind component but only around 9 knots .

Here is table in UTC and degrees True, same decode and disclaimer as before departing from offshore Vila at 11am Friday local = 08 0000UTC go SSE to 18S then go east to Navula Passage

UTC- HH:MM|----Lat:/ Long----:| hPa |  lull~avg~gust |Brg-Kt|TWA|Drift@BrgーT|Sig~ocnl

at 18S turn east ,  light head winds

(and Bob includes similar information for every 4 hours for the next 4 days!)

ETA Navula passage Sunday morning.

Route distance 522.03nm|  route time 2d 19h 04m||

Anyway for those into weather and in need of someone you can trust, then I highly recommend MetBob as do, many others. While I can forecast the east coast of Australia pretty well once you get outside of your home territory I truly believe it is mistake to attempt to call the shots on one’s own.  Sure there are a myriad of sites I look at in tandem with MetBob’s suggestions and so far my own view of how the trip will be from my own research has panned out pretty much in line with Bobs.  That being said, however, it would be a mistake in my view to not use a weather service.  Bob McDavitt’s website can be found at:




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