NDFD Verification Help

What is this website?

This site contains some basic verification results for selected weather elements (e.g., temperature, dew point, wind speed, etc.) from the National Digital Forecast Database (NDFD). We are still working on these pages. Please send comments and suggestions to the email address in the Contact section of this page.

How to Use This Site

The left section contains several categories of menu options from which the user can select. As prompted by the "Welcome" message on the right, first select a month. The projection menu appears for maps, but not plots, since each map is unique to a projection, while the plots contain all projections.

The main section displays the data and statistical products (currently, maps and plots) as selected by the menus on the left.

The left section contains menus you can use to select the verification product in which you are interested. You will need to first select a month from the top menu. Notice that as you make selections, the options available in the other menus can change.

The next category is called Element. The weather elements for which verification is available are displayed.

The next category is called Cycle. Currently, results based on 00Z and 12Z NDFD forecasts are available.

Next, select Product desired. Current options are plot and map. Plot files are graphs of statistics for all available projections. Map files are thematic maps of the statistics.

Lastly, for maps, which have individual results for projection, a Projection menu is provided.

Please note: All statistics for a given selection are presented in the main section. If Dew Point Map is selected, then maps of the MAE and Bias are given.

Available verification

These weather elements are available:

  • Max Temp
  • Min Temp
  • PoP 12
  • Dew Point
  • Sfc Temp
  • Wind Speed
  • Wind Dir
  • Sky Cover
  • Wind Gust
  • Relative Humidity


These product types are available:

  • Map
  • Plot


The set of statistics, and thus plots and maps, will change according to the weather element. Please note that the statistics available are dependent on the weather element chosen. The statistics used, particular to a certain weather element, are MAE (mean absolute error), bias (forecast minus the observation), Heidke Skill Score, Fraction Correct, Brier Score, and Relative Frequency. These are defined in the Definitions section of this page.

To print a particular image (maps or plots), click or right-click on the image, then choose Print from your browser's File menu.

Definitions of weather elements

  • Max Temp: Daytime maximum temperature is defined as the highest temperature observed from 7 AM to 7 PM LST. Note that maximum temperature is associated with the 24-h MOS projection from 0000 UTC, 36-h MOS projection from 1200 UTC, 48-h MOS projection from 0000 UTC, and so on.
  • Min Temp: Nighttime minimum temperature is defined as the lowest temperature observed from 7 PM to 7 AM LST. Note that minimum temperature is associated with the 24-h MOS projection from 1200 UTC, 36-h projection from 0000 UTC, 48-h projection from 1200 UTC, and so on.
  • PoP: Probability of Precipitation (PoP greater than or equal to 0.01 in) for 12-h periods, specifically, 0000-1200 UTC and 1200-0000 UTC.
  • Sfc Temp: The ambient temperature observed at 2 meters above ground level.
  • Dew Point: The dew point temperature observed at 2 meters above ground level.
  • Wind Speed: The wind speed observed at 10 meters above ground level.
  • Wind Dir: The wind direction observed at 10 meters above ground level.
  • Sky Cover: The amount of sky covered by opaque clouds for the indicated hour. Beginning July 2007, NDFD, gridded MOS, and the verifying observations are consistent. Prior to that time, NDFD forecasts of opaque sky cover were compared to MOS forecasts and verifying observations based on total sky cover.
  • Wind Gust: The maximum wind speed observed at 10 meters above ground level. Note that if an actual wind gust is not observed at a given location, the wind gust assumes the value of the sustained wind speed.
  • Relative Humidity: The ratio, expressed as a percent, of the amount of atmospheric moisture present relative to the amount that would be present if the air were saturated. The verifying observation is computed from the ambient temperature and dew point 2 meters above ground level.


Contact NDFD

For further information about NDFD, please contact nws.ndfd@noaa.gov.