The role of mid-level dry intrusions in tornadogenesis associated with landfalling tropical cyclones in the western Gulf of Mexico

Landfalling tropical cyclones have the potential to produce tornadoes. Some produce outbreaks of tornadoes while others produce few or none. Examination of historical landfall cases may reveal the signficance of various parameters which determine which storms will produce outbreaks and under what conditions. Dry intrusions at mid-levels have the potential to substantially alter the thermodynamic structure of the tropical cyclone environment,with substantial enhancement of CAPE and surface-based instability. Based upon examination of historical West Gulf outbreak cases, a key factor appears to be mid-level intrusion of dry air into the northeast quadrant of the storm. Perhaps of equal significance, such intrusions were absent in null cases selected because of their geographical homogeneity to outbreak-producing storms.