Comparing Rainfall Observations in Hurricanes

NEXRAD WSR-88D estimated precipitation accumulation for Mobile, Alabama, area during Hurricane Gustav on Sept. 1, 2008. Source: NOAA National Climatic Data Center.

NEXRAD WSR-88D estimated precipitation accumulation for Mobile, Alabama, area during Hurricane Gustav on Sept. 1, 2008. Source: NOAA National Climatic Data Center.

Team Location: Mobile County Health Department, Alabama

Authors: Walt Clark, Vandana Raghunathan, Nathan Owen, Cynthia Erhardt, Josh Stodghill

Advisors/Science Mentors: Dr. Bert Eichold, Dr. Sytske Kimball, Dr. Jim Connors, Joe Spruce

Abstract: Often, tropical cyclone-induced freshwater flooding is overlooked as more attention is given to storm surge, high winds, and embedded severe storms. However, a Federal Emergency Management Agency study conducted from 1970- 1999 showed that tropical cyclone-induced freshwater flooding is responsible for approximately 59% of tropical cyclone-related deaths. Unfortunately, accurate and spatially continuous rainfall estimates of tropical weather systems are only measured when a system is in range for radar. As hurricanes impact the Gulf Coast every year, this project is urgent because it investigates the limitations and applications of available precipitation datasets. The study was conducted in two phases. In phase one, the Tropical Rainfall Measuring Mission (TRMM), the University of South Alabama Mesonet Network, and a combination of both datasets were compared against NEXRAD radar for three historic tropical landfalls. Regression analysis was completed for each case. The feasibility of incorporating TRMM data into the Mesonet network also was examined. The results of this phase benefited the Center for Hurricane Intensity and Landfall Investigation by providing a detailed comparison of available precipitation datasets and by demonstrating potential applications of TRMM precipitation data. The second phase of this project used TRMM to aid in hurricane preparation. Hydrologic models are often used to render detailed insights into specific flooding events. This study used hydrologic models to yield the overland flow within Mobile County, Alabama, that was caused by select tropical cyclones. Precipitation data, GIS thematic layers, and Digital Elevation Models (DEMs) were used to generate these overland flow model outputs. The results of this phase were presented to the Geology Department at the University of South Alabama. While outputs of the model were produced this term, hydrologic models require extensive calibration and validation of the input parameters. Future work could render an accurate model that utilizes TRMM data from tropical systems still out to sea, giving emergency managers advance insight into tropical induced freshwater flooding.

Video transcript available here.