Cloud tops are lower that cloud base !

  • Forecast for S34° E20.5° for 21-Dec-2017 at 10 am local time shows the following:
    Cloud base = 17272 ft Cloud tops = 13000 ft.

    Suggests the forecast model does not check for inconsistencies, leading to questionable reliability??

  • @propellerhead Hi, thank you for the question. These are two different parameters.
    Cloud Base is the level of first layer covering more than 50% of the sky. It is using ECMWF Ceiling parameter. We decided to use it instead of ECMWF Cloud Base Height parameter, which has a threshold at 1%.
    For more details on these ECMWF parameters see:
    So the parameter displayed on Windy can be described as "Cloud base of significant cloud layer".
    Now to the Cloud tops. This parameter does not have necessarily direct relation to the forementioned parameter, because it displays tops of convective clouds. It is mainly intended for prediction of large convective clouds which may reach top of troposphere. These clouds are very dangerous because of massive air turbulences.
    Details of the ECMWF parameter:
    And now about the reliability: We believe that both parameters can be useful for general aviation, so we added them to Windy, but we are not able to guarantee or even measure the reliability of them. We are happy for any feedback from pilots. The best feedback is experience from concrete flights. So if you or anybody else uses Cloud Base or Cloud Tops parameters in your briefing, please let us know how the prediction was successful and if it was useful for you or not.

  • Thank you for taking the time to provide a detailed explanation.

    In reality, would never use a single source in flight planning (I go IFR anyway), but I thought it was pleasantly absurd to put the problem in perspective :o))

  • Just noted that cloud tops are shown in feet, but cloud base in metres!! Can't see how to change this. Used to be both feet, so something has changed recently.

  • Found out how to change to feet clicking on the ribbon at the bottom of the screen !

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