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The North America Rapid Refresh Ensemble (NARRE) is a NOAA/NCEP operational ensemble forecast system based on time-lagging of 6 RAP and 4 NAM operational runs. It covers CONUS (in Grid #130, 13km in horizontal resolution) and Alaska (in Grid #242, 11km in horizontal resolution), and runs 24 cycles per day with hourly output of 12 forecast hours.
The NARRE provides ensemble guidance to aviation weather prediction, including both en-route products (icing, turbulence, jet stream, convection, etc) and TAF products (visibility, ceiling, fog, reflectivity, etc). There are three types of ensemble guidance, including mean, spread and probability with various thresholds. During the time-lagging more recent runs are given higher weights, with which the ensemble mean, spread and probability are computed.