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Old 10-08-2018, 11:09   #1
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Predict Wind: Which model

So I have been using just the regular free predict wind to get local weather forecasts for daysailing.

They have 4 models, many times with quite a bit of difference. I am not sure how to interpret these and which I should be using. Is one more accurate than the other? I read their suggestions, but still not helping vs. going to the noaa maps, listening to the TV, weather underground.

I am not looking to cross the ocean, just want to know what the winds are going to be for the weekend to go sailing or not. Thanks.
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Old 10-08-2018, 11:15   #2
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Re: Predict Wind: Which model

I use a free app called Windy and have had pretty good luck with it. It's not always accurate, but then again no one is always accurate about the Chesapeake.
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Old 10-08-2018, 12:11   #3
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Re: Predict Wind: Which model

Not an easy task, logging and plotting forecast against actual data. I tried far a few weeks in Portugal and found the GFS model was plenty accurate for our needs. The times of the fronts started to drift a bit after a few days but , say , 3 or 4 days out it was pretty good.
The 2 models predictwind run themselves I found to be not great, seemed to drift wildly quite quickly. ECMWF seems to be the preferred model for longer timescales.
Windy just gets better all the time, https://www.windy.com
Comoare various models if you want.
Opencpn is an excellent grib viewer as well with the grib plug in, turn on the gust display to see the fronts much cleared.
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Old 10-08-2018, 12:57   #4
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Re: Predict Wind: Which model

There are two primary models. The GFS from US NOAA and ECMWF from Europe. You can play with both models on windy.com and do your own comparisons for your area. The models are better offshore as they tend not to take the land effects into account near shore.
The other models on Predictwind are based on these models and are more marketing hype than anything else.

For near shore, short term predictions your local NOAA marine broadcast is as good or better.
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Old 10-08-2018, 13:25   #5
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Re: Predict Wind: Which model

One useful comment I saw here is that when the different models diverge a lot, it indicates unsettled conditions and any of the forecasts may be less accurate.

I use Windfinder and Windy and, in our area, find that none of the models are very reliable more than about 48 hours out.
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Old 11-08-2018, 08:43   #6
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Re: Predict Wind: Which model

What's people experience with ECMWF?
My experience with it in the Puget Sound for short term forecast (i.e., tomorrow's, or same day afternoon forecast in the morning) has been pretty awful so far, it seems widely inaccurate...
On a related note, I (unwisely) signed up for Windy Pro last week. I cannot see any difference from the free version in terms of features or accuracy... Am I the only guy who felt for the Pro?...
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Old 11-08-2018, 09:02   #7
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Re: Predict Wind: Which model

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Originally Posted by FabioC View Post
What's people experience with ECMWF?
My experience with it in the Puget Sound for short term forecast (i.e., tomorrow's, or same day afternoon forecast in the morning) has been pretty awful so far, it seems widely inaccurate...
On a related note, I (unwisely) signed up for Windy Pro last week. I cannot see any difference from the free version in terms of features or accuracy... Am I the only guy who felt for the Pro?...
Since you are using windy you can easily compare GFS with the Euro model. The land effects inside the Sound are not represented we'll in the models.
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Old 11-08-2018, 09:45   #8
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Re: Predict Wind: Which model

The "European models" are supposed to be more accurate simply because they've got more expensive computers working the data. NOAA should have a home-court advantage, but the historical data is available to everyone. NOAA's only advantage is having local ground stations reporting in real time.

A lot depends on where you are and how the weather patterns generally work, and you may have to take the wx forecasts with a grain of salt. When there are strong fronts coming one way, the forecast is usually reliable. When there is any mention of an occluded front, or conflicting air masses, that's when I put less faith in any forecasts because there are just too many random factors affecting which way things may go.
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Old 11-08-2018, 09:47   #9
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Re: Predict Wind: Which model

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Since you are using windy you can easily compare GFS with the Euro model. The land effects inside the Sound are not represented we'll in the models.
I have been comparing them, and my feeling is that GFS is somewhat more accurate (despite the buzz surrounding the Euro model).

Both models are vastly inaccurate on the Puget Sound, IMO, I think because of what you are saying, the land effects are not modeled accurately.

However, what I find strange, especially for the GFS, is that it seems to be doing a reasonable job predicting wind direction (when the wind is clocking, as it does in Elliott Bay at this time of year sometimes, the model is spot on), but it is very often far off predicting wind speed (it seems to over-estimate or under-estimate by a lot, with equal probability).

What is the best model for a place like the Sound, where the land effects are prevalent?
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Old 11-08-2018, 20:35   #10
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Re: Predict Wind: Which model

I think it's useful to compare a number of models/sources. There are good free ones like Windy but you get a lot more insight when you compare it with your local meteorological bureau or National Weather Service forecasts. If they don't match, then chances are conditions are (literally) unpredictable.
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Old 11-08-2018, 20:59   #11
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Re: Predict Wind: Which model

Predict wind is great in that you can see all four at once. If they all agree then they’re likely to be accurate. If they’re completely different then take your pick at random. I find ecmwf usefully better than gfs but they can often both be wrong by a good margin.
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Old 11-08-2018, 22:38   #12
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Re: Predict Wind: Which model

here in south pacific, after testing different approaches i follow ecmwf if all models diverge as it hit nail most often.

GFS is immediately after and study above two in tandem.

The other two only use for confirmation - ie if all 4 forecast same then strong probability.

Also if one component predicted similar, say time of arrival of strong winds, but other things diverge, will take time into account for higher probability forecast.

In throughs, forecasts are nearly meaningless and plan B is more important.

Observing sky, clouds, waves, animal behaviour, adds another dimension.

thats what i learned so far.
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Old 13-08-2018, 08:55   #13
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Re: Predict Wind: Which model

I've been using PredictWind, WindyTY and Chris Parker's Marine Weather Service for some time now, cruising the Atlantic coast from Rhode Island to the Eastern Caribbean and out to Bermuda.

I agree with the other replies stating that if the models align closely, then you can have high confidence that the forecast will materialize as predicted. Then the question is how to interpret models that are widely different?

In this case I use multiple strategies. First, if it is only one source that is way off, then I discount that in my mind, consider the others to be more reliable, but proceed with less confidence. Second, I consider the extremes that are forecasted across all models and decide if my vessel, passengers and crew are up to it if the worst case does materialize. Third, I consider the sail plan and my bailout options, is there a place to tuck in if conditions deteriorate?

That process has proven successful, and just remember, if your gut says, don't sail, you can always find fun in port!
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Old 13-08-2018, 09:02   #14
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Re: Predict Wind: Which model

So how does everyone actually get a figure for forecast accuracy?

I've tried it in port before with web local airport wind/gust gauges from near 10m high. Then with a lot of copying and pasting data into spreadsheets and graphing you could see the patterns emerging as fronts went through. On a boat our human bias must be near impossible to completely filter out.
Plus, as a very experienced ex weather forecaster on a UK forum is fond of saying - "The wind itself doesn't even know what it's doing to within a Beaufort force or 2.."
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Old 13-08-2018, 09:09   #15
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Re: Predict Wind: Which model

For what I am looking for, which is say on Wed to look what the winds on the bay will be on Sat, to see whether or not it will be a good sailing day, I think should have very high reliability.

The local weather forecast for this 48 hour in advance is pretty darn accurate, they just don't have marine forecast details as when you want to go to the beach, whether or not the winds are at 7 or at 13 makes no difference. But if you are thinking of going sailing, that difference makes ALL the difference!

So with predictwind, I find it odd that 2 of the 4 models agree, and say 1 is quite a bit different.

See attached, which is the next 2 days. First red highlight, 3 are pretty close, so that is probably what is going on, though ecmf is WAY off. Next highlight, on Wed has PWG and GFS saying very little wind, with the other saying OK wind. Which to believe?
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