Subject: RECONSTRUCTION OF SURFACE WIND FIELDS FOR TROPICAL CYCLONES AFFECTING FLORIDA BAY
Samuel H. Houston
Dr. Mark D. Powell
Dr. George A. Soukup (NOAA/AOML/HRD)
Ms. Summer C. Spisak (NOAA/AOML/HRD)
Mr. Luis. Amat (NOAA/AOML/HRD)
Objective: The primary objective of this research project is to
reconstruct episodic/catastrophic meteorological events which
critically affect the South Florida ecosystem.
Rationale: Tropical cyclones are believed to exert considerable
influence on the health of Florida Bay. Wind fields associated with
these storms generate surface stress and an associated response in
the bay circulation patterns and sediment transport. Because the
"multiple pond-bank" nature of Florida Bay inhibits sediment
transport forced by relatively weak wind conditions, hurricanes are
believed to play a critical role in removing or transporting
sediment from the bay. Severe winds associated with tropical
cyclones may also contribute to ecosystem health as a result of the
post-storm decay of organic material damaged by the wind and storm
surge. In order to assess the response of Florida Bay to episodic
wind events, circulation and ecological modelers would benefit from
wind field analyses based on reconstruction of past events.
Method: Gridded tropical cyclone surface wind fields are being
generated from real case analyses and numerical model simulations to
produce a catalog of datasets. Research scientists will be able to
quickly retrieve data from this event/regime archive for use in
circulation model simulations/predictions, hydrological modeling,
natural systems restoration, and biological impact studies. We plan
to analyze the most significant storms to affect Florida Bay over
the past century. In so doing we will attempt to show a variety of
wind field affects on Florida Bay which could comprise an archive of
the types of extreme events that can be expected over the next
century. Data will be processed to achieve a consistent framework in
terms of averaging time, height and exposure. For storms with few
data available the wind profile fit currently used in a planetary
boundary layer model developed by Shapiro (1983) and implemented by
Vickery and Twisdale (1995) will be adapted to construct a
background field. These data will then be objectively analyzed using
the Spectral Application of Finite-Element Representation (SAFER)
method (Ooyama 1987, Franklin et al. 1993). This method uses cubic
B-splines to minimize the difference between the input observations
and the analysis. The methods used to standardize the input data for
analysis are described in Powell et al. (1996) and Powell and
Houston (1996, 1997). The scale of the analysis is controlled by the
analyst depending on the features that need to be resolved. Snap
shots of the streamline and isotach fields for each storm will be
generated for a 4 x 4 degree lat-lon domain centered on Florida Bay
at 6-12 h intervals, depending on the translation speed of the
storm. This domain should also be suitable for those interested in
studying extreme wind affects on the southern end of the Everglades.
Images of the wind fields are archived on our World Wide Web (WWW)
site (http://www.aoml.noaa.gov/hrd/Storm_pages/frame.html) for
access by Florida Bay researchers and gridded fields will be
generated upon request. These fields should be capable of import to
geographical information systems for correlation studies with other
geo-referenced fields such as mangroves, reefs, and turbidity
Accomplishment: In November of 1994, NOAA/AOML/HRD hosted the South
Florida Atmospheric Modeling Workshop (NOAA, Nov. 1994), attended
by 40 researchers representing meteorology, hydrology and physical
oceanography from south Florida's research community. Attendees
expressed the need for a catalog of meteorological events/regimes
which critically affect the South Florida ecosystem. Gridded
datasets from this archive could be accessed for
circulation/ecological model simulations, hydrological modeling,
natural systems restoration, and biological impact studies. Based on
this need we reconstructed surface wind fields for tropical
cyclones that affected Florida Bay. For example, the Labor Day
Hurricane of 1935 (Figure 1), Hurricane Donna of 1960 (Figure 2) and
Hurricane Betsy of 1965 (Figure 3) wind fields are now available.
The tracks of these hurricanes through Florida Bay may have
contributed to flushing the bay. As shown by the streamlines in
Figures 1 and 2, the flow over the bay was dominated by east and
northeast wind directions, which may have forced sediment to the
southern portion of the bay as the Labor Day Hurricane of 1935 and
Donna approached the area from the southeast. In addition, the
strong winds in excess of hurricane force along the fringes of the
bay damaged mangroves and other vegetation leading to decay of large
amounts of organic material in the northern part of the bay. In
contrast, the center of Hurricane Betsy (Fig. 3) moved nearly
westward over the bay. This was a weaker hurricane than in 1935 or
1960, but it would have likely had a significant affect on the bay.
Once gridded surface wind fields are available on our WWW site
(http://www.aoml.noaa.gov/hrd/Storm_pages/frame.html), they will
assist circulation modelers to determine how the bay responds to
South Florida Atmospheric Modeling Workshop (NOAA, Nov. 1994)
Franklin, J. L., S. J. Lord, S. E. Feuer, and F. L. Marks, 1993:
The kinematic structure of Hurricane Gloria (1985) determined from
nested analyses of dropwindsonde and Doppler data. Mon. Wea. Rev.,
Ooyama, K. V., 1987: Scale controlled objective analysis. Mon. Wea.
Rev., 115, 2479-2506.
Powell, M.D., S. H. Houston, and T. A. Reinhold, 1996: Hurricane
Andrew's landfall in South Florida: Part I: Standardizing
measurements for documentation of surface wind fields. Weather and
Forecasting, 11, 304-328.
Powell, M. D., and S. Houston, 1996: Hurricane Andrew's Landfall in
South Florida. Part II: Surface Wind Fields and Potential Real-time
Applications. Weather and Forecasting, 11, 329-349.
Powell, M. D., and S. H. Houston, 1997: Surface wind fields of 1995
Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne at landfall. Mon.
Wea. Rev., (In press).
Shapiro, L. J., 1983: The assymmetric boundary layer flow under a
translating hurricane. J. Atmos. Sci., 40, 1984-1998.
Vickery, P. J., and L. A. Twisdale, 1995: Wind field and filling
models for hurricane wind speed predictions. J. Structural
Engineering, ASCE, 121, 1700-1709.
Project overview page