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Old 12-09-2016, 06:32   #1
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Forecasting Models for the Strait of Gibraltar

Hi everyone,

just wondering if somebody has some insight on how accurate is the GFS (or some other model) for the acceleration zone on the strait of Gibraltar? I am planning to cross from the Atlantic to the Med sometime this week and our trusty boat is just too slow under motor to simply wait for a no wind window as so many around here seem to do. So we actually want to go thru sailing but we have been warned that the wind there is frequently a couple of Beauforts over what has been forecasted. This got me thinking.. well.. if the forecast is always under .. wouldn't the forecasters at some point simply add 10 Knots to their predictions?

So the question is.. for this stretch.. is the acceleration of the strait already factored in the models or does one really look at the forecast and add a couple of Beauforts on top of that? I understand that a weather model doesn't really take into account small local effects and such but the straight of gibraltar appears to me like a significant enough geographical feature to be accounted for in the models.. no?

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Old 06-10-2016, 04:17   #2
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pirate Re: Forecasting Models for the Strait of Gibraltar

The Straits of Gibraltar are typically unpredictable.. to many variables however if you follow common sense you'll do what many assume on hearing a forecast.. winds and sea's 'could' be upto 50% greater or lesser than forecast..
As you own a boat thats a dog.. pull into Barbatte.. or anchor outside then when the 3hr tide goes favourable run to Tarifa and do the same.. then run through the Straits for Gib.. quite simple if you don the thinking cap.

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Old 07-10-2016, 01:56   #3
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Re: Forecasting Models for the Strait of Gibraltar

Thanks for the reply .. For the Internet records here is what we found out and what worked for us. We stayed overnight in Barbate and left on a forecast of light winds 5 hours before HW Gibraltar so we could be around HW Gib - 3 south of Punta Camarinal .. Yeah we are *that* slow under motor. The poniente was scheduled to pick up later which it did so by the time we passed Tarifa we had 25 knots right behind us so it was a fairly swift passage and with the current in favour we were doing "warp" speed .. For us a whopping 8.5kts over ground :-) we got in to Gibraltar still with a favourable tide even though we lost an hour due to a fallen boom .. Ja .. right there before Tarifa. What are the odds?

Anyhow.. Just some pointers which might help other smaller boats doing the crossing. Info on the Internet is some times contradictory. For example after Gibraltar, I am sorry to say Reeds is wrong or rather misleading. There it said the easterly current runs further up the coast HW-3 like near Tarifa. This is definitely not so. On that stretch of coast it runs actually mostly west! We found this info on a Spanish website and experienced it later ourselves.

Oh and as far as the models .. After cruising the area I would say GFS tends to underestimate the winds while the NEMS 4km usually paints a scarier picture than what one finds at least near the coast. ECMWF I found fairly accurate .. But the best was whatever the forecast from the agencia meteorológica de Espańa on VHF said.. Not surprising they had it bang on :-)
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