Tuesday, 14 May 2002: 10:45 AM
Visibility Forecasts from RUC20
At least five characteristics of the new 20-km Rapid Update Cycle (RUC) being implemented at NCEP in early 2002 will lead to improvements in visibility forecasts. These include higher horizontal resolution (from 40km to 20km), improved versions of the MM5/RUC mixed-phase cloud microphysics and RUC land-surface schemes, assimilation of GOES cloud information modifying RUC 1-h hydrometeor forecasts, and an improved visibility algorithm which was originally based on the Stoelinga-Warner method. Ongoing 3-h verification against METAR visibility observations is being conducted for forecasts from both the RUC40 (RUC2) and RUC20. Results from these statistics indicate a considerable improvement from the RUC20. These results will be presented in detail at the conference, along with case studies of model visibility forecasts and observations. The paper and presentation will also illustrate the effects of RUC20 changes on visibility forecasts. This effort is being carried out under funding from the FAA toward improved national ceiling and visibility forecasts.