The rapid update cycle (RUC) is an atmospheric prediction system that consists primarily of a numerical forecast model and an analysis system to initialize the model.
The RUC was designed to provide accurate short-range (0- to 12-hr, later expanded to 18-hr in 2010) numerical forecast guidance for weather-sensitive users, such as those in the aviation community. 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 runs 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 is still only once an hour (the standard interval for ASOS observation reporting), and with current computational limitations and the time required to assimilate all of the data, there is approximately an hour delay in producing the forecasts. Because of this, it is common practice to use a one-hour forecast from the RUC as a current analysis, as the one-hour forecast comes out only a few minutes before the time it is forecasting for. There is also little possibility for error in a one-hour forecast, meaning that the RUC's one-hour forecast will not usually vary greatly from the actual state of the atmosphere at that particular point in time.
The RUC is scheduled to be replaced by the rapid refresh (RR) model, based on the WRF, though the date for the transition has been pushed back several times and it is uncertain when, or if, the transition will ever actually take place.[1]
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