What does this percentage sign stand for?

shuai liu 2

Suty

@shuai-liu-2 Hello, this percentage value describes available predictability for that day. More info about this here.

shuai liu 2

@Suty Thank you very much for your explanation, I understand now. By the way, which one is more accurate for hiking and mountain trekking, ECMWF or meteoblue AI?

Suty

@shuai-liu-2 I would recommend using the compare forecast function to see all available models for your location. Then you can make more reliable decision about your plans, when you can compare all of these forecast models.

shuai liu 2

@Suty “Because of possible uncertainties, we thus indicate two forecast-probabilities in our forecast information:
Predictability: The calculated probability of occurrence of the forecasted weather for the entire day and for all weather variables.
Precipitation probability: The probability of the occurrence of precipitations.”

Where can I find precipitation probability in the forecast panel? I can’t locate it, and only Predictability is shown.

Suty

@shuai-liu-2 We don't offer this dataset in Windy right now.

shuai liu 2

@Suty Okk,thank you.

pgilbrea

@suty I correctly guessed the meaning of predictability, but counterintuitively the value doesn't change when you change model. Is this a bug or is the predictability value an aggregate of all the models?

idefix37

@pgilbrea
I guess that predictability is the spread of forecasts from all weather models at a given time. Based on Meteoblue calculations for a set of models included in their Multimodel.
If you find a predictability computed by ECMWF for AIFS for instance, in this case it is the spread of the Ensemble forecast members.
But in Windy it is based on the predictably of the set of models computed by Meteoblue in their multimodel.

pgilbrea

@idefix37 said in What does this percentage sign stand for?:

But in Windy it is based on the predictability of the set of models computed by Meteoblue in their multimodel.

I think I understand. Hopefully it is not the predictability of the Meteoblue multimodel in particular, but uses the same calculation method to aggregate all available models for a location. If so, that's an exciting new feature! (I'm in North America and meteoblue doesn't do a great job near me.)

idefix37

@pgilbrea
You said

Is this a bug or is the predictability value an aggregate of all the models?

So, you finally know what that means.
But I am not sure you are right, because the individual predictability of all the models available on Windy is identical to that of Meteoblue AI model, which relies on about 20 models.

pgilbrea

@idefix37 Ah, I see. A bit deeper dive on this forum led me to a cool description you gave back in 2023 of the Meteoblue AI model. In case someone else is interested and following along:

@idefix37 said in Meteoblue resolution:

I'm curious to know what the resolution of Meteoblue is that Windy uses?

The Meteoblue model, called Meteoblue AI by this Swiss company, has no resolution because it is not a gridded model.
In short this model is “averaged” from a dozen of models with different resolutions from 2 to 40 km. Then the result is corrected according to local discrepancies usually observed. So it is only available at point forecast.

Will Windy be able to visual display Meteoblue forecasts like they do with ECMWF, GFS, etc …?

No, for the same reason said above.
It is the reason why the weather maps in the Meteoblue website are plotted from ICON, NEMS, GFS, NAM, HRRR, IFS 40km, UKMO, MF, GEM, etc…. but NOT from their Meteoblue AI model which is only shown in local meteograms.

Now my understanding is that the predictability percentage is specifically from the meteoblue model, but the value is an aggregate of way more models. Interesting! I look forward to playing with this new information!

Oxize

@Suty Why are the percentages the same for each model whatever i choose. I though this percentage is based on models with all sub elements like rain, moisture, wind, pressuure, etc?

idefix37

@Oxize
Have you read the article quoted by @suty ?
See more explanation.

HawaiiDude

Thanks. The predictability is a really helpful inclusion to the interface.