Terrain effects



  • As a keen and frequent yacht and dingy sailor I find that wind direction and speed are often affected by the local terrain. This can be a navigational and even safety issue as well as significant in racing. Currently your wind directions and speeds are uniform over any localised area. In reality, around, for example, the mountainous islands of the Ionian Sea, Greece or the inlets of my local lake in Devon, Uk, direction and speed are a function of the terrain and local heating effect on it. Your maps includes the contour information that would be required along with the time of day and sunlight forecasts.

    Incorporating terrain effects would make Windy invaluable to sailors.



  • @davidbarrow
    Wind (and other weather data) are outputs of weather models. Those models have to calculate on a 3 - dimensional grid of points. The nearer the points are together, the better will the model represent the atmosphere and topography. A practical problem is that small horizontal grids need more levels in the vertical and shorter time steps. This requires more computing power.

    Available computing power in 2018 limits grid lengths to 9 km for ECMWF, 7 km for ICON etc. For a good represantation of local winds around small islands we need smaller grid.
    In the future, the weather models will provide data in a finest grid, including small islands. So, will provide more realistic representation of the impact of topography on coastal winds.
    BUT .... we must keep in mind ....
    Small scale prediction requires high resolution data. Without such observational data, claims for forecasts to be exceptionally accurate, are meaningless.



  • .... similar "terrain effect" to temperature
    https://community.windy.com/topic/4476/temp-in-caribbean

    Also see how different model grids, affect the represantation of winds over mountainous islands
    https://community.windy.com/topic/5327/the-influence-of-topography-on-wind

    P.S. glad to hear that you sail in Ionian Sea ! Do you recognize the village in the background of my profile?
    https://community.windy.com/user/meteo-gr



  • @meteo-gr
    I appreciate your points about grid size and data. However, contour data from the map could be used to predict how the general wind direction within the grid would be deflected by the terrain, eg be deflected around high points and as in crosses the shore line. This would be an addition level of modelling within the current grid rather than the current modelling on a smaller scale.



  • @meteo-gr
    Where is it?
    It looks lovely but I don’t recognise it.



  • @davidbarrow this kind of modelling needs supercomputers which cost ~100M EUR



  • @davidbarrow
    It's Parga, Greece.


    10 NM east from Paxoi islands.
    If you sail in the area, you must also visit Sivota

    and the secret beach of Alonaki (39.2057445, 20.5045539)


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