Regional Differences in the Spatial Patterns of North Atlantic Tropical Cyclone Rainbands Through Landfall

Tropical cyclone (TC) precipitation impacts are difficult to predict due to rapid structural changes during landfall and few studies into how these changes vary regionally. This research examines spatial changes in light (0.254 mm h(-1)) and heavy (5 mm h(-1)) precipitation based on landfall location along the Atlantic and Gulf of Mexico coastlines using three spatial metrics: 1) area, 2) closure (proportion around storm center), and 3) dispersion (spread from storm center). Overall, we find that the largest spatial changes occur from landfall to 24 hours after landfall, likely due to eyewall breakdown. By subsetting TCs by landfall location, we find that heavy precipitation is more likely to become better organized in the approach to landfall in Gulf landfalling TCs. Post-landfall, Gulf storms decrease in size significantly, whereas Atlantic storms become asymmetrical but do not decrease in size. Extratropical transition (ET) versus dissipation after landfall does not explain these differences in precipitation around landfall. To further subset results, we apply a k-means clustering algorithm separately to the Gulf and Atlantic coastlines. We find that 5 mm h(-1) dispersion increases in Atlantic clusters (n = 3) but decreases in Gulf clusters (n = 3), especially in the western Gulf TC cluster. Additional insight into the other metrics is limited due to small sample sizes. Future studies should examine the physical mechanisms responsible for these differences so that operational forecasters and emergency management can be better equipped to aid in public preparedness when TCs make landfall.