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The Rapid Update Cycle (RUC) is a NOAA/NCEP operational weather prediction system comprised primarily of a numerical forecast model and analysis/assimilation system to initialize that model.

It was developed to serve users needing frequently updated short-range weather forecasts, including those in the US aviation community and US severe weather forecasting community. The Rapid Refresh is the next-generation version of the 1-h cycle system, planned to replace the current RUC by late 2009. The Rapid Refresh (RR) will use a version of the WRF model and the Gridpoint Statistical Interpolation (GSI) analysis largely developed at NCEP/EMC.