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National Digital Forecast Database Information


Status of NDFD Elements as of
July 8, 2009

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General Information

Interactive Forecast Preparation System (IFPS)

The creation of NDFD starts with the formulation of digital forecasts at each WFO. This, in turn, required the development and implementation of efficient methods whereby the results of the thought processes of WFO forecasters could be put into digital (or numerical) form. The Interactive Forecast Preparation System (IFPS) has been developed for this purpose. It has been under development for a number of years (Ruth et al. 1998, Peroutka et al. 1998), but the processing power of the Advanced Weather Interactive Processing System (AWIPS) was necessary to make it feasible nationwide.

Interactive forecast preparation represents a substantial change for forecasters. Instead of manually typing a myriad of forecast products tailored for specific user communities (e.g., public, aviation, marine), forecasters rely on various data interpretation and editing techniques to prepare forecasts of weather elements in a common digital database from which forecast products will be automatically composed and formatted.

IFPS incorporates three methods for entering digital forecasts into the database which are: matrix entry, graphical entry, and model interpretation.

Matrix entry--The Interactive Computer Worded Forecast (ICWF) (Ruth and Peroutka 1993) employed this method, making interactive earlier technology for producing text from digital forecasts (Glahn 1970, 1979), and has been integrated into IFPS. While this method was successful (Rezek 2002; Dickman 2002) and still provides a method for "fine tuning" data entered by other methods to specific times and locations, it has been largely replaced by the graphical method.

Graphical entry can insert forecasts into a gridded database at a spatial resolution essentially bounded only by computer power (Wier et al. 1998). The graphics depict an underlying grid of values. The forecaster works with the graphics until he or she is satisfied with them. Then, the underlying grid becomes the "forecast."

Model Interpretation involves working directly with numerical model output (Ruth 1998) or its interpretation (e.g., MOS) to forecast sensible weather elements. Model interpretation, through IFPS, requires a higher level of understanding and training and is not yet being used at most WFOs. As weather prediction models improve, direct interaction with the models through this interface will probably become more prevalent.

Each of these interfaces provides a viable way of entering data into the digital database. The forecasters at WFOs choose the interfaces they use. The forecasts can have a time resolution of 1 hour at short ranges and 3 or 6 hours at longer ranges. Spatial resolution is expected to be at least as fine as 5 km with full implementation of IFPS in September 2003. These digital forecasts automatically result in the routine textual and voiced forecasts and provide a foundation for the development of a new generation of grid-based NWS products, including the digital forecast database itself.

For more details on IFPS, visit