65th IHC Booklet/Program (pdf - 4.9MB) - Office of the Federal ...

Testing of a New Parametric Tropical Cyclone Wind Model for Implementation
in the Gradient Wind Asymmetric Vortex Algorithm (GWAVA)
to Drive Storm Surge Prediction Models
Craig A. Mattocks 1 , Vincent T. Wood 2
(cmattock@rsmas.miami.edu
1 University of Miami/Rosenstiel School of Marine and Atmospheric Science;
2 NOAA/OAR/National Severe Storms Laboratory
A new tropical cyclone wind model,
developed at the National Severe Storms
Laboratory (NSSL), is presented that is
primarily designed to depict realisticlooking
tangential wind profiles that can
better fit the wind structure around a tropical
cyclone. The parametric wind profile
employs five key parameters: maximum
tangential wind, radius of maximum
tangential wind (RMW), and three powerlaw
exponents that shape different portions
of the velocity profile. One of the exponents
explicitly controls the broadness and
sharpness of the peak locally in the annular
zone that encompasses the tangential wind
maximum.
To assess the performance of the new
parametric wind model, gridded H*Wind
horizontal wind analyses for Tropical Storm
Dolly (2008), Hurricanes Katrina (2005),
Ike (2008), Danielle (2010), Earl (2010),
and Igor (2010) were used as input. These
tropical cyclones were chosen because the
wind fields are highly asymmetric. The
gridded fields were interpolated using a
bilinear interpolation technique to construct
each radial profile of total wind speed from
the storm center defined in a cylindrical
coordinate system. At each of 360 radial
profiles, optimization of the initial five
model parameters was performed using the
Levenberg-Marquardt method that solves
the nonlinear least squares problem for
Poster Session – Page 24
curve-fitting applications. The calculated
root-mean-square errors were computed to
evaluate the accuracy of the fitted and
analytical tangential wind profiles. Using the
fitted model parameters, a two-dimensional
wind field was reconstructed by
interpolating the 360 radial profiles to the
Cartesian coordinate system. The parametric
wind model has shown considerable skill in
accurately replicating tropical cyclone wind
fields that compare favorably with those in
the H*Wind analyses (Fig. 1). This versatile
wind model will soon be implemented in
GWAVA to improve the wind forcing that
drives storm surge prediction models.
Fig. 1. Fit of the NSSL tropical cyclone
parametric wind model to a horizontal wind field
(kt) from an H*Wind analysis for Hurricane Ike
(2008). Blue circle indicates the limited region
in which the winds are fitted. TC stands for
tropical cyclone