John Kaplan
              AOML/NOAA
        Hurricane Research Division
        4301 Rickenbacker Cswy.
        Miami, FL 33149

             Mark DeMaria
                and
            Michelle M. Huber
         National Hurricane Center
           11691 SW 17th Street
           Miami, FL 33165

        A Preliminary Evaluation of Forecasts from
        an Empirical Inland Wind Decay Model for 
        Hurricane Erin (1995)


In early August of 1995, Hurricane Erin made landfall along both the East 
Coast and Panhandle of Florida before eventually becoming extratropical 
and dissipating  near the Virginia/Maryland border. Erin's track across 
the data rich Florida Peninsula made it a good candidate for evaluating 
an Empirical Inland Wind Decay Model (IWDM) developed recently at  
HRD (see Kaplan and DeMaria 1995) and employed  by the National 
Hurricane Center during the 1995 hurricane season for the first time.
The IWDM model is a simple two-parameter model 
developed based upon the assumption that tropical cyclone wind speeds 
decay exponentially with time after landfall. A correction term which 
accounts for storms that remain relatively close to the coastline after
moving inland was also incorporated into the model. The IWDM has 
several potential applications. The model can be used for planning purposes 
to estimate the maximum sustained wind that might be experienced at 
different inland locations for storms of various intensities and speeds 
of forward motion. It can also be used to provide
an estimate of the swath of inland wind speeds produced by a 
landfalling TC. This particular model application (see Figs. 1 and 2)
was evaluated for landfalling Hurricane Erin by comparing the IWDM
predicted wind speeds to the winds at all available inland surface
observing stations. Erin's structure and intensity at landfall 
required to produce the forecast wind swath were determined from
information contained in operational NHC hurricane
advisories. The important conclusions that can be made from these
preliminary evaluations are the following: 
  
    The IWDM provided a reasonably good estimate of the swath  
of the maximum sustained winds, although the forecast winds were
somewhat too high. 

    Model sensitivity tests (not shown) indicated that employing 
experimental surface wind analyses produced for Erin by Sam
Houston and Mark Powell of HRD resulted in improved IWDM forecasts.

    The collection of additional landfall data sets is required to 
refine the IWDM, especially for the wind swath application. 

References:

       Kaplan, J. and M. DeMaria, 1995: A simple empirical model for 
predicting the decay of tropical cyclone winds after landfall. J. Appl.
Meteor., 34, 2499-2512.

Acknowledgments. We would like to thank Sam Houston and Ed Rahn of
HRD for providing some of the data that was employed in this study. 
This research was partially funded by the Federal Emergency Management
Agency (FEMA).   



Figure Captions:

Fig. 1. Wind swath produced using the IWDM for Erin's landfall on 
        Florida's East Coast. The observed maximum sustained surface
        winds are depicted in black and have been adjusted to a height 
        of 10 m and to an averaging time of 1-min to be consistent
        with the IWDM. The units are knots. 

Fig. 2. Same as Fig. 1 for Erin's landfall on the Florida Panhandle.