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5th August 2017 A dilemma - weather forecasts contradict each other!!

Early Saturday 5th August 2017 A dilemma - weather forecasts contradict each other!!

I’m using both the COAMPS and NDFD forecasts, downloaded as attachments to email subscriptions from Saildocs, (Thanks to Jim Corenman and Stan Honey for generously organising that possibility as a free Sailmail service to all sailors!)

Since we’re running less than 100 miles off the coast, the US Navy’s COAMPS forecasts should be the more reliable since they take land effects into account. When available, the new NOAA NDFD forecasts are now generally more reliable for offshore than the GFS grib files, since they come from the daily weather forecasts produced by humans, not solely from computer programs, although I can’t say I’ve had a major problem recently with the GFS files. I get the impression that the NDFD files are possibly better near the coast than the GFS - but I’ve not been able to test my theory that much.

My problem now lies with the major discrepancy on my route between the two programs I’ve been using (COAMPS & NDFD) in a day’s time. They agree on what to expect for the coming 24 hrs or so, but then diverge completely after that - the one showing calm conditions near the coast for the following two days and the other showing strong winds spreading right in to the coast instead…

The problem is that my plan of action will be totally different for the two scenarios… In the one case, just keep on as we are now, in the other, head more offshore to position us to take advantage of the strong wind to sail back in … I’ve even noted the line where it would be good to tack around, assuming the forecast strong wind direction is correct… But there’s no point in adding miles by heading offshore if the wind is not then strong enough to make it worthwhile sailing back towards the coast… or, even worse, if there is then no wind to sail in!

I can only hope that over the coming day, the two are more in agreement on what to expect on Sunday and Monday.

Written by : Jeanne Socrates