Tropical Meteorology Special Symposium
19th Conference on Probability and Statistics


Physical processes associated with surface wind field uncertainty in Hurricanes Katrina and Rita (2005): Use of present and future observational tools

Peter G. Black, NOAA/AOML/HRD, Miami, FL; and E. W. Uhlhorn, J. F. Gamache, R. D. Knabb, J. Carswell, P. S. Chang, S. Lorsolo, R. E. Hood, L. Jones, I. PopStefanija, and A. S. Goldstein

Three new airborne observing technologies are synthesized to obtain the time evolution of the structure and intensity of Hurricanes Katrina and Rita as they approached landfall in the northern Gulf of Mexico. In situ GPS dropsondes, the new Stepped Frequency Microwave Radiometer (SFMR) and the airborne Tail Doppler radar on NOAA WP-3D aircraft are used to synthesize storm structure and surface wind fields. Conventional flight level and surface data are analyzed separately to illustrate the range in uncertainty in the surface wind fields that can be deduced depending upon the observational platforms used. Observations obtained from the Integrated Wind and Rain Atmospheric Profiler (IWRAP), flown in selected hurricanes from 2002-2006, and observations planned from the next generation scanning SFMR system called Hurricane Imaging Radiometer (HIRad), both scheduled for operational implementation in 2008 on the NOAA WP-3D, are discussed to illustrate how these new observing platforms can be used to further reduce uncertainty in hurricane vertical boundary layer structure and surface horizontal wind field structure.

The observations from both storms in the study show a remarkable transformation from a compact CAT4/5 storm offshore to a considerably weaker storm during the landfall process. Transformation is documented from sharply-peaked wind profiles with radius of maximum winds near 20 km and peak surface winds near 70 m/s to broad wind maxima with radius of maximum wind of 60-70 km and peak winds of 45 m/s- but spread over a 120 km wide swath to the right of the center. This change resulted in conditions maximizing the devastating storm surge in Katrina's case and in maximizing damage to offshore structures in Rita's case.

The use of IWRAP for continuous vertical profiling of boundary layer winds and HIRad for expanding the swath of surface wind observations beyond the aircraft track, illustrate new tools that will become available over the next few years to reduce uncertainty in surface winds that impact coastal populations and play a pivotal role in estimating destructive storm surge and wave run-up near landfall. Impacts of the analysis of these data in real time as well as post event synthesis of the surface wind field proved significant for Katrina and Rita, and likely will continue to be significant in the future as new SFMR systems become available operationally on the fleet of ten WC-130J's operated by the 53rd Weather Reconnaissance Squadron and IWRAP and HIRad systems become operational on the NOAA WP-3D aircraft.

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Joint Poster Session 1, Tropical Cyclones and Probability/Statistics Posters
Monday, 21 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B

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