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Old 17-06-2016, 21:28   #1
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Gfs vs predictwind, oh and windgusts

Ive been playing around with predictwind for a bit. Normally just use staight GFS files but predictwind fiddles with them (and the canadian base data) and claims they are better.

Just curious what you have experienced with regards to the accuracy of the predictwind and other models vs GFS. I know here in aussie the BOMs meteye uses a number of base models and refines them. They work pretty well.

Another question is on the windgusts grib field. Only just started using them on windyty and predictwind. From my reading it seems to use instability, moisture and temp to give an idea of the possible gustiness of the wind. Seems to be stronger near fronts which makes sense to me. How accurate and useful have you found it? Is CAPE and windgust likely to be useful to predict thunderstorms and severe weather events? All these new toys to play with...
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Old 17-06-2016, 23:35   #2
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Re: Gfs vs predictwind, oh and windgusts

It's not like PW doesn't use the GFS model. They may also use another model, but so can you. Before a passage I like to download multple GRIB models. Then I pick the one that looks like it has the best sailing conditions.
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Old 18-06-2016, 00:20   #3
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Re: Gfs vs predictwind, oh and windgusts

Ha, yeah that sound like the plan, except being a pessimistic soul I usually pick the worst one!

What have you found has been more accurate overall. I have always been inpressed by the accuracy of the standard unadulterated gfs files especially offshore, but I guess I have gotten used to adjusting them to account for local effects. I suspect thats what predictwind does, but I havent been using it enough to really know.

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Old 18-06-2016, 00:53   #4
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Re: Gfs vs predictwind, oh and windgusts

Mostly I use GFS. If I'm sitting around wondering why we haven't left yet then I might download some of the others and see how well they agree. I think agreement among the models is the most reassuring. On the upper west coast of the US I'd use the GFS model for basic planning, but use the US Navy model to try and get a better feel at how the Capes would be. It kind-of seemed to do a better job on the Capes.

I'd like to see some examples where PW did better than GFS on the local/land effect stuff or out 4 or 5 days. I really don't buy into the high resolution GRIBs. For my use they are just not accurate enough need more than .5 deg and 1 is fine. For passage making the GRIBs have inaccuracies in their wind speed, wind direction as well as the timing of these. So there's lots of error in the 3+day GRIBs. Useful for planning, but I don't want to fool myself into believing their accuracy and acting accordingly.
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Old 18-06-2016, 04:25   #5
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Re: Gfs vs predictwind, oh and windgusts

I like to compare the different models on weather model gfs - oceania - precipitation [base + 3] - weatheronline=
I think generally the local ensemble models perform better for local forecasts, so I imagine Predictwind uses one or creates its own.
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Old 18-06-2016, 04:35   #6
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Re: Gfs vs predictwind, oh and windgusts

Interesting stuff to say the least. Especially as I've always been a big DIY weather fan, as well as teaching it whenever there's the opportunity. So I'd love it if you guys would share some links to your favorite weather resources & tools. Including the ones mentioned in this thread thus far.
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Old 18-06-2016, 05:59   #7
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Re: Gfs vs predictwind, oh and windgusts

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Originally Posted by Lodesman View Post
I like to compare the different models on weather model gfs - oceania - precipitation [base + 3] - weatheronline=
I think generally the local ensemble models perform better for local forecasts, so I imagine Predictwind uses one or creates its own.
Thats a very interesting site, thanks. It has access to more base models than I am used to using. Makes me realise just how much behind the 8 ball I am on the latest models.

The ensembles such as the gfs ens seem significantly different even offshore, so it makes me wonder exactly what they are "ensembled" with.

It is amazing how things have changed in the last 15 years. In the past we struggled to find any weather information out past a few days. Now we are swamped what is easily availible.
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Old 18-06-2016, 07:15   #8
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Re: Gfs vs predictwind, oh and windgusts

I signed up with predictwind but on a recent uk-portugal ended up just using gfs gribs, predictwind just seemed too "sensitive" and gribs are a familiar source and known accuracy. That said it was more of a kneejerk reaction. I've spent months before logging windguru and actuals from Google Maps APRS wx stations and a local airport on a big outdoor live event where wind was a big deal for working conditions. It ain't easy! Evernote helps for saving daily screenshots to try getting a handle on the accuracy of predictions so I know gribs in Azerbaijan are very accurate upto a few days ahead
So really I can't comment too much on predictwind, and apologies, but I doubt anyone else has done the logging required to get a reasonable handle on such a thing. Our monkey brains just aren't reliable enough to say much without looking at a load of data.

Anyone fancy a load of logging
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Old 18-06-2016, 07:46   #9
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Re: Gfs vs predictwind, oh and windgusts

Gusts 50% on top of the sustained wind. I do not use gusts data and as a rule forecast 'gusty' to my clients whenever in frontal / tropical wave or cloudy area. Also inshore when the land is flat and prone to heating up. Also inshore on the lee side of tall land.

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Old 18-06-2016, 09:49   #10
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Re: Gfs vs predictwind, oh and windgusts

I have used Predictwind for several years on the pro level. I can say I have not found it to accurate. Having used it in the Pacific, Indian and the Atlantic oceans. This is definitely the last time I will pay for it. Just using wind guru currently and find it perfect for me.
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Old 18-06-2016, 12:24   #11
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Re: Gfs vs predictwind, oh and windgusts

Pw is not not bad. Founder gave access to me from the very early days
I suggest it for East Med
However there is a major competitor for this area the Poseidon project at Poseidon.gr which offers great accuracy
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Old 18-06-2016, 17:03   #12
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Re: Gfs vs predictwind, oh and windgusts

We have used PW for over a year now while crossing the Indian and S Atlantic oceans and passages in between. PW provides four weather models; straight up GFS and CMC (Canadian) models and then they have their own based on the GFS and CMC inputs. As with most models you need to add a factor for increased winds, gusts ie 25-50%, then you get your actual.
We chose PW also for its routing which is based on any of the four above wind models, your boat polars, current, etc. I can never put my destiny into a computer program but it does provide us with a good starting point. Often we find ourselves deviating from the PW route for various reasons. Its a tool and we find it helps.
You also have access to GMDSS safety alerts and satellite images. All good stuff.
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Old 18-06-2016, 17:18   #13
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Re: Gfs vs predictwind, oh and windgusts

I like this one: https://www.windyty.com/?-27.471,153.024,3
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Old 18-06-2016, 17:43   #14
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Re: Gfs vs predictwind, oh and windgusts

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Isn't that just a pretty display of GFS?
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Old 18-06-2016, 18:39   #15
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Re: Gfs vs predictwind, oh and windgusts

https://earth.nullschool.net/ /8176 hf aus/local vmr/prep for wind at present
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