On 11 August, 1993, a new convection parameterization package has become operational for the National Meteorological Center (NMC) Medium-Range Forecast (MRF) model replacing a Kuo (1965, 1974) scheme that has been in operation for over ten years. The new scheme is a version of a simplified Arakawa-Schubert (1974) scheme that uses the mass flux concept to adjust the atmospheric temperature and moisture field. The new scheme uses quasi-equilibrium assumption as a closure and includes a downdraft scheme that is analogous to the updraft scheme. Testing of the new scheme in parallel during Northern Hemisphere Spring shows a consistent improvement in the precipitation forecast verified against the observations taken by the high density North America rain gauge network maintained by the National Weather Service. Improvement in the tropical climatology and the tropical cyclone prediction have also been noted.

National Weather Service (NWS)

United States