In collaboration with NCEP's multi-model Short-Range Ensemble Forecast (SREF) initiative, we have developed RUC SREF system targeting for both operations and research needs.

The RUC SREF system includes an interpolation package which interpolates NCEP's regional breeding modes onto RUC hybrid-coordinate grids; a preprocessor which prepares initial and lateral boundary conditions, land/ocean surface data and other fixed data files ready for model integrations; an operational forecast model (RUC); and a post-processor which packs the forecast data into GRIB format and derives all the other diagnosed fields.

Currently, RUC SREF runs twice daily with a total of 10 members. The SREF domain encompasses the entire North America including Alaska, Central America including the Caribbean Sea, the western Pacific including the Hawaiian Islands, and the western Atlantic. The forecast is run out to 60 hours with output every 3 hours. The horizontal spacing is 48 km.

The statistical verification scores show the mean errors from RUC SREF forecasts comparing against Eta analysis and Eta 12-km operational runs are reasonably small, and yet the forecast spread calculations show that there is significant variability among the forecast members.