Wrong wind data



  • Hi
    Can anybody explain why windy miss All wind speeds in ionian? Every day i moyice agsin failures in winds speed of 100 percent.really anoying


  • Moderator

    @vojkob
    Why do you think that windy miss all wind speeds in Ionian?
    I compare observed data (e.g. from meteo. stations in the coast) with forecast data
    and I don't see any great difference.
    79f29428-8587-4433-9e02-87b95b15b18e-εικόνα.png

    f345e79f-84c3-46c3-805b-9f2ddcdb7c0c-εικόνα.png
    .......


  • Moderator

    .......
    today (13 July) ECMWF gives 5 max 6 BFT.
    3c3e67eb-4a44-4170-9419-84416480a378-εικόνα.png

    with gusts up to 8 BFT in the Otranto strait
    12fada04-6529-4e3a-9635-7dc76e25f73a-εικόνα.png

    For tomorrow the forecast is for 3~4 BFT.
    2938efd5-eed5-42ae-b084-0c94c08782f4-εικόνα.png

    In what area you observed 100% failure?



  • We are in euffemia kefalonija, windy shows 8 knots wind, instead is 35knots

    I have same experience begore. Data are not precise enouvh to be usefull


  • Moderator

    @vojkob
    Thank you for providing the location where you observed such a big difference
    between reported and forecasted wind speed.

    The phenomenon you report is called "wind funnelling effect".
    50c85599-e10c-4d18-bdd6-53c7189b0483-εικόνα.png

    Agia Effimia (Keffalonia, Greece) is located in the south of narrow valley.
    d9449567-9160-433c-904f-b55d7cca9df1-εικόνα.png

    Steep mountains, 900m high, rise in the north and south of the valley
    with peaks only 2 milles away from each other.
    These days, the NW wind is funnelled, especially during the afternoon,
    resulting gusty northwesterlies.
    Light winds can often become much stronger when they are forced
    to converge and funnel through a narrow mountain pass.
    Unfortunatelly, a weather model with a 9 km resolution is unable
    to accurately depict the topography around the valley,
    and therefore will not accurately model the winds at Agia Effimia.
    Only human forecaster with knowledge of the local topography,
    as well as historical knowledge of how the land affects the wind in the area,
    can therefore predict the NW'ly wind at Agia Effimia with accuracy.


  • Moderator

    ....
    Following images show how a weather model with a finer grid,
    gives better forecasts in such conditions.
    8b03b589-f8af-4379-b3c4-b1cff0391d41-εικόνα.png

    But, for even better forecasts in such a complex terrain,
    high resolution (grid=1 km) weather models needed.


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