Principal Investigators:
Collaborating scientists:Michelle Huber and Mike Hopkins (NHC/TPC)
Rationale: That significant damage and loss of life often occurs inland after landfall (as
happened in Hurricane Hugo of 1989 and in Andrew) underscores the need for accurate forecasts
of tropical cyclone winds inland. When Hugo and Andrew made landfall, no operational
hurricane prediction models provided intensity forecasts over land. Subsequently, HRD
developed an empirical model for prediction of the decay of hurricane winds after landfall for
the U.S. south of 37 N. With financial support from the Federal Emergency Management
Agency (FEMA) the Inland Wind Decay Model (IWDM) has been recently completed (Kaplan
and DeMaria 1995). It is a simple two-parameter model which assumes that tropical cyclone
wind speeds decrease exponentially after landfall and that the rate of decrease is a function only
of the intensity and speed of hurricane motion at landfall. The IWDM has three basic uses. It
can be used to estimate the maximum sustained wind near the TC center as a function of time, to
predict a swath of wind speeds as the hurricane moves inland, and to support preparedness
planning with maps of the maximum possible wind speeds for hurricanes of various landfall
intensities and speeds of motion.
Method: Starting with the 1995 Hurricane season, forecasts from the IWDM were made available to forecasters at the National Hurricane Center/ Tropical Prediction Center (NHC/TPC) for select landfalling tropical cyclones. FEMA used the model for hurricane evacuation planning, also starting with the 1995 Hurricane season. An evaluation of the IWDM overland wind swath forecasts was performed for the two landfalling U.S. hurricanes (Erin and Opal) of 1995. The intensity and structure of these hurricanes at landfall required to run the IWDM, were obtained from the last NHC/TPC advisory prior to landfall. Comparison between forecast and observed winds were made at all inland sites where surface wind observations could be obtained. In addition, a comparison of the IWDM forecast maximum sustained wind near the TC center was performed for all 5 TCs that made landfall in the U.S. during 1995. For this coo