Minimal pressure at centre of intense low (Dorian). NOAA:916mbar; Windy:956mbar (MOD EDIT: Actual data vs Forecast data?)



  • Dorian is currently (as of this writing) reported as 916 mbar ("Minimum central pressure") by NOAA.
    But on Windy, the centre is shown as 956 mbar. (Or a near to centre isobar?).

    Is there a reason for the mismatch? Can this be improved? Windy intense lows are consistently reporting higher than 'official' source actual minimal lows.

    References below: A) NOAA Dorian status for 1100UTC and B) Current Windy image for approx same time.

    A) Excerpt from NOAA Dorian status
    SUMMARY OF 700 AM EDT...1100 UTC...INFORMATION

    LOCATION...26.7N 78.2W
    ABOUT 35 MI...50 KM ENE OF FREEPORT GRAND BAHAMA ISLAND
    ABOUT 120 MI...190 KM E OF WEST PALM BEACH FLORIDA
    MAXIMUM SUSTAINED WINDS...165 MPH...270 KM/H
    PRESENT MOVEMENT...W OR 280 DEGREES AT 1 MPH...2 KM/H
    MINIMUM CENTRAL PRESSURE...916 MB...27.05 INCHES

    B) Image sample from Windy
    36a15ba3-7391-4d69-b886-4d58535e5ce3-image.png



  • The barometric pressure on you site is way off. True is 916. You have 956.


  • Moderator

    Unless I am mistaken it seems that you may be comparing:

    • FORECAST data displayed on Windy (from a Forecast issued at 0800 UTC)

    WITH

    • ACTUAL data issued by NOAA (from an excerpt issued at 1100 UTC)

    Below you can see the Forecast data from ECMWF is indicating 960mb, but the Actual data (at the top left) is indicating 9hPa (900mb).

    Switching to a different Model also gives different Forecast pressures, with GFS and NAM suggesting 995mb and 936mb respectively.

    But Actual data should of course be more valid and up to date than previous Forecast data.

    2019-09-02 15.53.07 - Windy_ Hurricane tracker - Google Chrome.jpg


  • Moderator

    Please see many other threads regarding this subject, including this recent one:

    https://community.windy.com/topic/9456/dorian-wind-speed-and-pressure/2

    And the detailed discussion here:

    https://community.windy.com/topic/4415/why-is-wind-speed-in-hurricanes-so-wrong

    Additionally, Windy does not create any forecast data but instead only visualises forecast and actual data received from various third party providers.

    There are many useful but also complex and expert level tools and data available via Windy, therefore the user must always take care:

    • To understand what information they are displaying and viewing
    • To understand from where and when the information was sourced
    • To understand what this information actually means.

    Comparing Forecast data with Actual data can be a common mistake.

    Around 1300 UTC the Windy Hurricane Tracker was reporting wind speeds of 142kn / 164mph / 264kph.

    Hope this helps :)



  • I get the difference. Yet, Windy never (it seems) shows the minimum to be as low as the actuals. It should at least make a mistake in that sense from time to time...


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