Cloud to ground lightning in tropical cyclone: a study of 34 West Atlantic tropical cyclones from 1986-1996

Abstract

Cloud to ground (CG) lightning characteristics and patterns were investigated for 34 tropical cyclones for the time period 1986 to 1996. Spatial analysis of CG lightning relative to both compass directions and the direction of motion were compiled. Additionally, a radial analysis of this data was performed within both a 300 km radius and a 50 km radius range. Finally, all analyses were stratified into all tropical cyclones and hurricane categories for further consideration. The National Lightning Detection Network recorded 307,593 CG lightning flashes within 300 km of the storms in this study. Negative flashes had an average first stroke peak current of -49 kA and a mean multiplicity of 2.7. Positive flashes occurred at a rate of 5.3 percent, with a mean peak current of 43 kA and 1.2 multiplicity average. Detected CG lightning characteristics changed significantly with a network upgrade in 1994. CG lightning flashes for all tropical cyclones favored the area south and west of the cyclone center. However, taking into account storm relative motion, the majority of flashes shifts to the front and right sections of the storm. Radial plots indicated lightning frequency increased throughout the domain, with a maximum between 270 km and 300 km. Hurricanes, however, indicated flashes occurred most often in the north and east quadrants. When adjusting for storm motion, the activity shifts to the right with some evidence of individual rainbands in the rear section. Radial plots indicated the increased organization of hurricanes, with a weak maxima in the convective eyewall, a minimum in the stratiform area, and a strong maximum in the outer rainbands. Further analysis indicated a higher frequency of CG lightning flashes in hurricanes suggests a state of hurricane strengthening or weakening. However, there was no direct correlation in the observed lightning frequency with a given change in the central pressure of the hurricane.