Introduction to NCEP's time lagged north american rapid refresh ensemble forecast system (NARRE-TL)

Rapid Refresh (RR) is a WRF-ARW based new generation regional model developed by NOAA/ESRL/GSD which will be implemented at NOAA/NWS/NCEP in the fall of 2011 to replace the current RUC model to provide domestic aviation weather guidance. Compared to RUC, a new feature of RR is that it covers not only the CONUS but also Alaska and its surrounding waters - a domain not much smaller than that of the North American Mesoscale (NAM). According to a common plan between GSD and NCEP, both RR and NAM will be combined and extended to become NARRE or the North American Rapid Refresh Ensemble system when the computing capability is increased in a few years to support hourly NAM and multiple ensemble members. In the mean time, however, in order to fully utilize existing NAM & RR forecast output data, a time lag technique is applied to establish an hourly updated ensemble system primarily for aviation weather, which we are calling the Time Lagged North American Rapid Refresh Ensemble system, or NARRE-TL. NARRE-TL is to replace the current RUC-based Very Short Range Ensemble Forecast (VSREF) system. Using the same method as in the VSREF, the NARRE-TL uses 4 previous NAM runs, 6 previous RR runs and one current RR run to form an 11-member ensemble system. The spatial resolution and aviation products in the NARRE-TL are the same as those in the VSREF but with output domains for both CONSUS and Alaska. Like VSREF, one of the major advantages of the NARRE-TL is that it is not resource demanding, can be updated hourly and provides probabilistic information. As an experiment, the NARRE-TL aviation products over both CONUS and Alaska have been generated and displayed at NCEP web site http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE/web_site/html/icing.html and http://www.emc.ncep.noaa.gov/mmb/SREF_avia/FCST/NARRE_Alaska/web_site/html/icing.html. This talk will give a brief description of the NARRE's configuration and product development and will show some examples of typical guidance products.