The fields provided here are products of NCEP's mesoscale numerical weather prediction (NWP) model known as the Early Eta Model and its associated 4-D data assimilation system, known as the EDAS (for Eta Data Assimilation System). The name "Eta" derives from the model's vertical coordinate known as the "eta" or "step-mountain" coordinate. Whereas the Eta forecast model generates forecast fields out to 36 hours from initial states at 00Z and 12Z, the EDAS generates eight 3-hourly initial states or analyses during each 24-hour period, utilizing a vast set of observed data.

Together, the mesoscale Eta Forecast Model and the Eta Data Assimilation System will be hereafter referred to as the ETA/EDAS.

A good reference describing the Eta Model is the 1994 paper by Tom Black of NCEP in Volume 9 of the AMS journal Weather and Forecasting, pages 265-278.

Two other references describing the Eta/EDAS system are:

A list of extended references is given here.