WAFS Data Help


The NWS Display of WAFS Grids for Turbulence, Icing, Cb Cloud and Wind is a graphical representation of the grids issued jointly by the World Area Forecast Centers (WAFCs) in the US and the UK. These grids are sanctioned by the ICAO and the FAA for use in flight planning. They are available for various levels from forecast hours 6 to 36, in three hourly time steps, in GRIB2 format. This product will provide users a way to display the grids at all levels and time steps via a web page with a GIS display. Users will be able to overlay multiple levels and forecast parameters and loop through the time range, as well as pan and zoom on the map.

For more information about the grids themselves, see http://www.icao.int/safety/meteorology/WAFSOPSG/Guidance Material/Guidance on the Harmonized WAFS Grids for Cumulonimbus Cloud, Icing and Turbulence Forecasts - 11 September 2012.pdf

Purpose/Intended Use: The purpose of the display is to provide a rudimentary way to visualize the WAFS Grids for Turbulence, Icing, Cb Cloud and Wind. This visualization is intended for users who need to check that their own display software is correctly decoding the GRIB2 files and properly displaying the gridded data in graphical format. It is also intended to serve as a common reference point for the NWS and its customers when discussing the WAFS forecast data.

Plot Description: The WAFS data display is a visualization of the WAFS aviation grids that allows users to view the fields on a global display. The grids include:

  • Clear Air Turbulence (CAT) at 200, 250, 300, 350 and 400 mb
    CAT values run from 0 to about 35. Values above 5 are visualized.

  • In Cloud Turbulence (InCldTurb) at 400, 500, 600 and 700 mb
    InCldTurb values run from 0 to about .035. Values above .005 are visualized.

  • Icing at 500, 600, 700 and 800 mb
    Icing values run from 0 to about 1. Values above .7 are visualized.

  • Cumulonimbus (CB) horizontal extent and tops
    CB horizontal extent values run from 0 to about 1 and reflect amount of grid cell covered by CB. Values above .3 are visualized.

    CB tops values run from 0 to about 60,000 feet and show max tops of CBs. Values above 30,000 feet are visualized.

  • Wind Speed at 300, 400, 500 and 600 mb
    Wind speed values run from 0 to about 170 knots. Values above 60 knots are visualized.

The weather selector drop down allows the user to select three layers to overlay along with an opacity value for each layer. The time controls are a drop down under the valid time in the upper right. The controls allow the user to step through the forecast times (< and >) or loop through the forecast times. When looping the < and > control the loop speed slower and faster respectively.