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vicb / windy-plugin-sounding

Sounding plugin for Windy.com.
https://www.windy.com/
MIT License
19 stars 5 forks source link

Inaccurate parcel trajectory #2

Open KOPRajs opened 4 years ago

KOPRajs commented 4 years ago

Hi, I've just discovered your plugin. It is very nice indeed but the results seems overly optimistic in comparison to our local site http://www.xcmeteo.net. This site is using the GFS model so you can compare the results with your plugin using the same input data when using GFS as well (You can use some well known spots like e.g. Kobala.).

The parcel trajectory seems to be the most significant difference. I've looked through the sources and if I understand it right it seems that you simply draw the parcelTrajectory() +3 degrees to the right from the surface temperature:

const thermalT = skewTSel.tSfc(state) + 3;

Can you elaborate on this a bit? Why 3 degrees?

Thank you.

vicb commented 4 years ago

Sorry for the delay, I only your question now.

I use 3C because it seems like it's working for me - that'a an empirical value.

Do you have other suggestions ?

KOPRajs commented 4 years ago

Hi, after a brief consultation with other pilots I'm not sure if it should be a simple constant value at all, but at least the value of 3 degrees seems to be too high to me. I would suggest a value of 1.5 degree which I saw somewhere as a reasonable value.

vicb commented 4 years ago

For sure it is not a constant in real life. Many parameters are at play here: cloud cover, wind, moisture, pressure, ...

In my opinion 1.5 is no better or worse than 3C - models are models and should be interpreted by humans. And honestly given the poor GFS accuracy I don't think that it would make a diff.

It takes some experience to be able to interpret soundings considering the other influencing. I don't think it is possible today (ever ?) to have super accurate result directly from the model.

I have found 3C to be give reasonable results. May be I'll implement a way to change this 3C difference but for now I think it would confuse people looking at different things.

BTW in your initial message you discuss about this plugin vs xc meteo. I think it would be interesting to add a vs real life.