How Landfall Affects Hurricanes

When a tropical cyclone makes landfall (the center of the low pressure moves onshore), this almost always results in a weakening of the tropical cyclone. This weakening will be observed as both an increase in the minimum surface pressure and a decrease in the maximum observed surface winds. This weakening occurs for two reasons: 1) the warm sea surface temperatures which have been acting as an energy source for the tropical cyclone are no longer present and 2) the rough land surface introduces friction from obstacles like trees and buildings, which work to slow down the wind speeds within the tropical cyclone.

The friction introduced by the rough land surface, as compared to the smoother ocean surface, also increases the potential for isolated tornadoes to form within the tropical cyclone. The friction from landfall introduces more turbulent flow around the tropical cyclone, which can lead to quick, brief spin-ups in the form of tornadoes. These tropical cyclone tornadoes are usually not nearly as strong as some of the tornadoes observed with supercells in the Great Plains region of the United States, but they can cause much stronger localized wind gusts and are very difficult to predict. Because of the counter-clockwise rotation of tropical cyclones, tornadoes associated with hurricanes and tropical storms almost always occur in the front-right quadrant of the storm. For example, if a tropical storm is moving due north, then tornadoes will be most likely on the northeast side of the landfalling tropical cyclone. Likewise, if a tropical cyclone is moving due west, then tornadoes will be most likely on the northwest side of the landfalling tropical cyclone.