<![CDATA[Isoline chart not changing with altitude]]>
  • Moving the altitude slider to select, say 500mb isoline view does not display a 500mb isoline chart.
  • Most times the isoline labels will show the new barometric pressure, but not always.

    • aca0b54a-c960-4f62-bbd3-4e869a1e7c57-image.png

    9ae779b5-8ff4-452e-8945-c7ca7f58a76d-image.png

    ]]>    https://community.windy.com/topic/14391/isoline-chart-not-changing-with-altitudeRSS for NodeThu, 13 Aug 2026 18:12:23 GMTThu, 19 Nov 2020 15:56:55 GMT60<![CDATA[Reply to Isoline chart not changing with altitude on Fri, 20 Nov 2020 18:15:29 GMT]]>@idefix37 Thank you for the explanation. Now I understand!

    ]]>    https://community.windy.com/post/62939https://community.windy.com/post/62939Fri, 20 Nov 2020 18:15:29 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Fri, 20 Nov 2020 17:10:00 GMT]]>@Migration
    What you show is Geopotential heights at 500 hPa, expressed in dam = decameters (1 dam is 10 m). That has nothing to do with hPa units. Windy shows the same isolines but in meters (Windy does not show Geopot. heights in feet). At 500hPa the mean Geopotential height is about 5500m or 550dam. See the legend of the same ECMWF map:
    https://www.ecmwf.int/en/forecasts/charts/catalogue/medium-z500-t850?facets=undefined&time=2020112000,0,2020112000&projection=classical_europe

    You say that sailors don’t consider Geopotential heights? They should do it:
    https://vos.noaa.gov/MWL/dec_08/milibar_chart.shtml

    ]]>    https://community.windy.com/post/62921https://community.windy.com/post/62921Fri, 20 Nov 2020 17:10:00 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Fri, 20 Nov 2020 13:29:23 GMT]]>@idefix37 With the sider all the way down, windy shows isobars (isolines of pressure) at sea level.
    With the slider moved up to 500mb, I expect windy to show a chart of isobars (isolines of pressure) representing conditions in the mid- troposphere. This level is at an altitude of approximately 5,500 meters (18.000 ft), relative to a standard atmospheric pressure of 1013.25mb at sea level.

    Windy does display this chart, if geopotential height is selected. The isobar labels then represent pressure as equivalent altitude in feet.
    Not much use to a sailor. I want to know how to display isobar (isolines of pressure) values in mb instead of feet.
    Here is an example standard 500mb (500hPa) chart from ECMWF.

    https://stream.ecmwf.int/data/gorax-blue-009/data/scratch/20201120-0600/a0/render-gorax-blue-009-6fe5cac1a363ec1525f54343b6cc9fd8-Z3CX9u.png

    99ea9725-a670-48cf-92df-eb8079094e72-image.png

    ]]>    https://community.windy.com/post/62885https://community.windy.com/post/62885Fri, 20 Nov 2020 13:29:23 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Fri, 20 Nov 2020 08:18:36 GMT]]>@Migration
    Isobares give you lines with the locations at the same pressure. Those pressures are expressed in hPa and always refer to the sea level.
    Isohypses (geopotential) are lines which connect locations having the same selected pressure that you choose, for instance 500hPa, but at different altitudes or heights. We talk about height, not pressure so it is expressed in m or dam. At 500hPa, altitude should be around 5500m but depending of the weather conditions, height can be higher (anticyclonic conditions) or lower (cyclonic conditions). This is the interest of those geopotential data, to see if the situation at the ground level is connected with the altitude : high pressure at sea level connected with high geopotential.

    ]]>    https://community.windy.com/post/62821https://community.windy.com/post/62821Fri, 20 Nov 2020 08:18:36 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Fri, 20 Nov 2020 08:11:24 GMT]]>@Migration
    Pressure at 500hPa is uniformly 500hPa ! There is no way to do what you want because the altitude slider does not show a real altitude but a pressure level. It’s how the weather models work.

    ]]>    https://community.windy.com/post/62820https://community.windy.com/post/62820Fri, 20 Nov 2020 08:11:24 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Thu, 19 Nov 2020 22:53:58 GMT]]>Great, thanks. How do I display pressure isobars at 500hPa labelled with hPA value instead of height .

    ]]>    https://community.windy.com/post/62776https://community.windy.com/post/62776Thu, 19 Nov 2020 22:53:58 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Thu, 19 Nov 2020 18:59:07 GMT]]>@aidzer
    The Geopotential height isolines are available in the mobile app but only with a tablet, not with a phone.
    I have got the screenshot in my previous post here above with my iPad.

    ]]>    https://community.windy.com/post/62755https://community.windy.com/post/62755Thu, 19 Nov 2020 18:59:07 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Thu, 19 Nov 2020 18:26:19 GMT]]>@idefix37 is this also applicable on mobile app?

    ]]>    https://community.windy.com/post/62749https://community.windy.com/post/62749Thu, 19 Nov 2020 18:26:19 GMT    <![CDATA[Reply to Isoline chart not changing with altitude on Thu, 19 Nov 2020 19:03:30 GMT]]>@Migration
    What you show are Isobars i.e. pressure isolines at sea level. They have no reason to change when you move the altitude slider.
    In altitude meteorologists use Isohypses which are the Geopotential height isolines i.e. the altitude of a pressure surface, for instance at 500hPa. To display these isolines, go to More layers and select Geopot. height.

    E8DEB7E8-6DE9-42FD-AB19-1C78D0E75EC5.jpeg

    In Windy they are expressed in metres.
    http://www.theweatherprediction.com/habyhints/76/

    ]]>    https://community.windy.com/post/62732https://community.windy.com/post/62732Thu, 19 Nov 2020 19:03:30 GMT