Evolutionary periods of precipitation distribution in tropical cyclones (TCs) are sometimes misrepresented in numerical weather prediction models due to the rapid nature of TC structure changes that accompany intensity change. To better understand quantitative changes in TC rainband structure around landfall, I quantify the spatial distribution of precipitation in 62 landfalling TCs along the Gulf of Mexico and Atlantic coasts of the U.S. between 1998 and 2014. The Tropical Rainfall Measuring Mission (TRMM) 3B42 product is utilized to assess three spatial measures of precipitation: 1) area, 2) closure, and 3) dispersion. Calculations are made using two rain rate thresholds, 0.254mm/hr and 5mm/hr, to capture and compare changes in light and heavy precipitation, respectively. Changes in TC precipitation are statistically different based on landfall location along the Atlantic vs. Gulf. Overall, dispersion (measure of centrality) is the most dissimilar metric due to variability between 0.254mm/hr and 5mm/hr results. Lighter precipitation decreases in area and expands away from the TC center, while heavier precipitation contracts rather than disperses in Gulf landfalling storms. A k-means clustering produces six landfall regions and reinforces the result of heavier precipitation becoming more central along the Gulf, while Atlantic landfalling storms exhibit decreased centrality. Significant differences were not found in storms that undergo extratropical transition or dissipate later in lifecycle. The holistic approach exhibited by this study reveals wide variability among a large dataset of storms making landfall; therefore, sub-setting techniques are helpful to hurricane forecasters in understanding the role of landfall location. / MS / As our coastal communities become progressively vulnerable due to increased urbanization and settlement along United States coastlines, natural disasters, such as flooding caused by hurricanes and nor’easters, will continue to cripple coastal populations. Strong winds, storm surge, and heavy rains upon landfall during tropical cyclones produce billions of dollars’ worth of damage to infrastructure and natural resources. By understanding structural changes of hurricanes in terms of the spatial coverage of rainbands before, during, and just after landfall, operational meteorologists will be better equipped to aid in public preparedness and provide improved rainfall forecasts to emergency management personnel. This research examines the structural changes in precipitation as hurricanes make landfall along the Gulf of Mexico and Atlantic coasts of the U.S. using three shape metrics; 1) area (2-D coverage), 2) closure (proportion around storm center), and 3) dispersion (spread away from storm center). Precipitation is subset into light (0.254 mmhr⁻¹ ) and heavy (5 mmhr⁻¹ ) rain rates in order to capture and compare the structural changes of 62 landfalling hurricanes between 1998 and 2014. I find that the average precipitation distributions of Gulf and Atlantic landfalling hurricanes at the time of landfall are similar; however, there are important changes in these distribution based on landfall location. Specifically, Gulf storms become larger and heavy rain contracts around the TC center, while Atlantic storms become asymmetric and spread out through landfall. These results demonstrate the importance of landfall location and the role that environmental factors may play in determining how hazards related to flooding can evolve along the U.S. coastline.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/96586 |
| Date | 03 August 2018 |
| Creators | Kirkland, Jessica Lynn |
| Contributors | Geography, Zick, Stephanie E., Carroll, David F., Ellis, Andrew |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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