YachtWeather vs. PocketGrib Apps - different forecasts?

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Planning a leisurely sail from Herring Bay to Knapps Narrows or Oxford this weekend.

At 2p on Saturday, PocketGrip calls for peak winds at 17.5kts where YachtWeather is predicting 7kts gusting to 11kts at the same time and location.

At 2p on Sunday PocketGrip calls for peak winds at 14.4kts where YachtWeather is predicting 13 kts gusting to 21kts.


What explains the significant difference in predicted winds on Saturday? Any suggestions on a third weather application that folks here find reliable and easy to use?

 

[Jackdaw]

Different forecast models.

NOAA creates one called the GFS. (Global Forecast Model). The Canadians has a great one as well, and does the UK. Each typically gives slightly different results. Many of these so-called 'wind services' use more than one, and sometime 'blend' them to create their 'own' model.

Most of these free or low cost apps simply use one or more of the free models. The more expensive ones (like PredictWind Premium) actually do their own value-add modeling on top of the big national services.

 

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Thanks for the background behind these weather apps. I downloaded PredictWind and subscribed for the premium. It matches YachtWeather's predictions for Saturday but calls for an additional 2 kts on Sunday.
Nice app. I like the forecast alerts. I will put it to use.

 

[BayMan]

Another free one to look at is Windfinder.

 

[Jackdaw]

Its a decent app, and the modeling is pretty good. For the premium service they basically take the most detailed GFS model and interpolate it to 1km. Then (the big deal) they use geographical land detail to model the effects of shore on the breeze. The NOAA model does not do that.

But after a while sailing in the same area, local knowledge fills that in. So we dropped it last year.

When we go offshore, we use the VERY GOOD Weather4D app.

http://www.weather4d.com/en/

This app allows you to choose what weather model to use, and can download the data directly to the app from their server. When we charter in Greece or other fun places, every morning we pull the data in. The forecast allows us to plan the day. We're that little blue dot in the center!

The PRO version does weather routing, taking in the performance characteristics of your boat (via Polars) to plot an optimized route based on wind. This is great for long offshore races. He we model our 367s route for the Trans-Superior. See how it varies from the straight rhumb-line.

 

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Good times today. Here getting back to Deale. Lots of wind out there but no way of determining which of the various applications had the best predictions (my Datamarine is down).

 

[dziedzicmj]

you can also try WindGuru.

My experience tells me that the local variations would determine which application works for you better. All of that is approximate and in many places the weather is very local (winds may vary by several knots 5 - 10 nm away).

If you check a few of these forecasts over time, you will figure out which model works for you locally.

I am afraid that none of the forecasts is "the best" globally.

 

[Ron20324]

...At 2p on Saturday, PocketGrip calls for peak winds at 17.5kts where YachtWeather is predicting 7kts gusting to 11kts at the same time and location.
///At 2p on Sunday PocketGrip calls for peak winds at 14.4kts where YachtWeather is predicting 13 kts gusting to 21kts....quote]

I was watching the weekend weather on http://www.ndbc.noaa.gov/data/Forecasts/FZUS51.KLWX.html
for a club sail, and I'd say Yachtweather had the best prediction, according to the weather we actually experienced. You could look at Thomas Point Light House weather station for hourly updates, and recent, after-the-fact, weather history that you could use to compare to the predictions.
http://www.ndbc.noaa.gov/station_page.php?station=tplm2