 Significant weather forecasting problems that occur in the 0- to 12-hr range include severe weather in all seasons (for example, tornadoes, thunderstorms, snow, and ice storms) and hazards to aviation (for example, clear air turbulence, icing, and downbursts).The RUC ran at the highest frequency of any forecast model at the National Centers for Environmental Prediction (NCEP), assimilating recent observations to provide very high frequency updates of current conditions and short-range forecasts.This update frequency was only once an hour (the standard interval for ASOS observation reporting), and with computational limitations and the time required to assimilate all of the data, there is approximately a one-hour delay in producing the forecasts.