MMM SEMINAR NCAR
Experiences with 0-36 hour Explicit
Convective Forecasting
with the WRF-ARW
Model: A Vision of the Future?
Morris L. Weisman
NCAR/MMM
During the past three springs and summers, 36 hour realtime forecasts were conducted daily with WRF-ARW using a 4 km horizontal grid resolution and explicit convection over the central and eastern US, using the 00 UTC ETA model for the initial state and boundary conditions. These forecasts were evaluated on a day to day basis by NWS forecasters and researchers across the country, and were also highlighted in the SPC/NSSL 2004, 2005 Spring Program. These simulations showed an uncanny ability at times to forecast the timing and location of significant convective outbreaks, and often accurately distinguished the basic mode of convective system organization (e.g., squall lines, bow echoes, MCVs, supercell lines, ordinary scattered thunderstorms, etc.). Significant benefits were also evident when considering the statistical properties of convection, whereby representing such processes ``explicitly'' seemed to be critical to properly representing the diurnal cycle and convective episodes. These results offer the community much hope that multi-day explicit convective forecasting could soon be valuable addition to existing forecast guidance. Still, a significant false alarm rate emphasizes the need for further research and model improvements.
This presentation will go on to highlight some of the known sensitivities/limitations as regards existing physics packages (i.e., pbl, microphysics, etc.) and resolution, as well as the need for a better representation of the initial state at the mesoscale, including, among other factors, the inclusion of ongoing convection.
Refreshments 10:15 AM
NCAR-Foothills Laboratory
Bldg 2 Auditorium (Rm1022)