Nested Grid Model

An example geopotential height and relative humidity forecast by the NGM

TheNested Grid Model(usually known asNGMfor short) was anumerical weather predictionmodel run by theNational Centers for Environmental Prediction,a division of theNational Weather Service,in the United States. The NGM was, as its name suggested, derived from two levels of grids: a hemispheric-scale grid and asynoptic-scalegrid, the latter of which had a resolution of approximately 90 kilometers. Its most notable feature was that it assumed thehydrostatic equation.

The NGM debuted in 1987, directly replacing thelimited-area fine mesh(LFM) model, which was immediately halted upon the NGM's debut. The NGM was also used to createmodel output statistics.Development of the model stopped in 1993. By 2000, the model was seen as obsolete, particularly formesoscalefeatures that were not hydrostatic, and was scheduled to be superseded by theGlobal Forecast System(GFS) in 2001. However, though the NGM ceased widespread use in the early 2000s due to the GFS and improvements in theEta model(later theNorth American Mesoscale Model), and the NGM's short-range LAMP products were phased out in 2006, NGM MOS products continued to be in significant general use (alongside the Eta/NAM and GFS) until March 3, 2009, when the NGM MOS products were discontinued.