The National Digital Forecast Database (NDFD) is a database put together by the National Weather Service (NWS) to provide forecasts of sensible weather elements (e.g., cloud cover, maximum temperature) on a seamless grid. The NDFD is currently given out to the public as a GRIB2 file. For more information about how and why the NDFD was created, please see the NDFD Home page
GRIB2 is the second version of the World Meterological Organization's (WMO) standard for distributing gridded data. It is described in the WMO GRIB2 Document FM92-X11 GRIB. For "web friendly" versions, either:
The problem, when the NDFD first came out, was that the only way to decode a GRIB2 message was to use the GRIB2 library. This required the user to write code, and then refer to the WMO's specifications to decipher the "meta" data (e.g., variable type, variable unit, reference date time, valid date time, etc). This defeated the original purpose of the NDFD which was to make the digital data easy to use by the public.
To resolve this the Meteorological Development Laboratory (MDL) created a driver for the GRIB2 library. The driver, known as "degrib" (aka "NDFD GRIB2 decoder"), was originally designed to:
To encourage the use of the NDFD, degrib was designed to run either via a Graphical User Interface (GUI), or from the command line, giving the user the flexibility to run the program manually or via a script or program. For additional portablilty, the GUI aspect of degrib uses Tcl/Tk (version 8.3.2).