Coupled HWRF-HYCOM Modeling System for Typhoon Forecasts

Typhoon forecasts from a coupled ocean-atmosphere modeling system are examined for the 2012 and 2013 seasons in the Western North Pacific (WPAC) basin. The model has been developed at the Environmental Modeling Center, NOAA/NWS/NCEP by coupling Hybrid-Coordinate Ocean Model (HYCOM) to the operational Hurricane Weather Research and Forecast (HWRF) atmospheric model. During the 2013 season, HWRF-HYCOM has been run in real-time typhoon in parallel, while the atmospheric model (HWRF) provided operational guidance to the forecasters at the Joint Typhoon Warning Center (JTWC). This parallel experiment provided an excellent opportunity to compare the prediction capability between the two systems and to assess the ocean role in Typhoon prediction in WPAC basin. Evaluation of the model performance includes verification of track and intensity forecasts between the two systems, followed by validating sea surface temperature (SST) cooling against fusion TMI-AMSRE observations. We will also investigate the importance of SST for typhoon intensity forecasts by employing a simple thermodynamic formula of the maximum potential intensity to tease out other environmental parameters. SST for the formula will include transitory HYCOM temperature and persistent Global Forecast System (GFS) temperature, and the atmospheric parameters will be the HWRF temperature and humidity. These results will be discussed in the presentation along with the forecast verification and the SST validation.