Evaluation of a GFDL hurricane model ensemble forecast system

An ensemble forecast system based on the GFDL hurricane model has been developed as part of the regional modeling effort for the Hurricane Forecast Improvement Project (HFIP). The ensemble forecast system was developed prior to the 2010 hurricane season and has been run in near real time for the 2010 and 2011 hurricane seasons. In this paper, we describe the design of the ensemble forecast system and present results from the 2010 and 2011 Atlantic hurricane seasons.

The perturbations for the 2010 ensemble system were designed with an emphasis on impacting the initial intensity and structure of the storms. For many of the members, the input parameters that define the target wind profile for the spin-up of the bogus vortex were modified. For 2011, this method was refined with additional members added to perturb the initial wind profile. Members were also added which modified the initial moisture field in the near-storm environment. In addition, several members were added that modified various components of the convective parameterization.

Results for both 2010 and 2011 Atlantic hurricane seasons indicate statistically significant improvements of the ensemble mean intensity forecasts over the control forecast. Results indicate positive, but smaller, improvements for track forecasts.