Spatial Variations of North Atlantic Landfalling Tropical Cyclone Wind Speed Decay over the Continental United States

Understanding tropical cyclone wind speed decay during the postlandfall stage is critical for inland hazard preparation. This paper examines the spatial variation of wind speed decay of tropical cyclones over the continental United States. We find that tropical cyclones making landfall over the Gulf Coast decay faster within the first 24 h after landfall than those making landfall over the Atlantic East Coast. The variation of the decay rate over the Gulf Coast remains larger than that over the Atlantic East Coast for tropical cyclones that had made landfall more than 24 h prior. Besides an average weaker tropical cyclone landfall intensity, the near-parallel trajectory and the proximity of storms to the coastline also help to explain the slower postlandfall wind speed decay for Atlantic East Coast landfalling tropical cyclones. Tropical cyclones crossing the Florida Peninsula only slowly weaken after landfall, with an average of less than 20% postlandfall wind speed drop while transiting the state. The existence of these spatial variations also brings into question the utility of a uniform wind decay model. While weak intensity decay over the Florida Peninsula is well estimated by the uniform wind decay model, the error from the uniform wind decay model increases with tropical cyclones making direct landfall more parallel to the Atlantic East Coast. The underestimation of inland wind speed by the uniform wind decay model found over the western Gulf Coast brings attention to the role of land-air interactions in the decay of inland tropical cyclones.

Automated summary

Understanding the spatial variation of tropical cyclone wind speed decay over the continental United States is crucial for hazard preparation inland. Tropical cyclones making landfall over the Gulf Coast tend to decay faster within the first 24 hours compared to those making landfall over the Atlantic East Coast. The presence of spatial variations in wind speed decay raises questions about the accuracy of a uniform wind decay model.