The distribution of convective precipitation in tropical cyclones after landfall

Cloud-to-ground lightning flash locations from the National Lightning Detection Network were used to identify and examine regions of convection in 35 Atlantic basin tropical cyclones from 1985-1999. Large azimuthal asymmetries in flash locations were seen for both the core (inner 100 km) and outer rain band (100-300 km) regions. Over 80% of the flashes in both the core and outer bands of tropical cyclones appear in the downshear quadrants of the storms, with core flashes having a downshear left and outer rainband flashes exhibiting a strong downshear right preference. Flashes were more frequent to the right of the track than the left, with core flashes tending to be in the right front and rainband flashes in the right rear quadrant with respect to motion. These asymmetries were seen when the storms were over both open ocean and the United States mainland.

For this presentation a subset of storms, only those with extreme rainfall events after landfall, will be examined. Lightning flash locations and rain gauge data will be used to explore the usefulness of the results of the previous study in predicting the location of convective rainfall in landfalling tropical cyclones. Three storms, Bob (1985), Harvey (1999) and Irene (1999), will be examined. Bob (1985) and Harvey (1999) produced flooding along Florida's Gulf coast and had large outbreaks of lightning in both the core and rainbands upon landfall. Irene (1999) also brought heavy rain to South Florida but had far fewer flashes than Bob (1985) and Harvey (1999).