The morphology of eyewall cloud to ground lightning in two category five hurricanes

Abstract

Data from the Long-Range Lightning Detection Network (LLDN), the Tropical Rainfall Measuring Mission (TRMM) sate11ite, and reconnaissance aircraft are used to analyze the frequency and location of cloud to ground lightning outbreaks in the eyewa11s of Hurricanes Rita and Katrina. Each hurricane produced eyewall lightning outbreaks during the period of most rapid intensification, during eyewall replacement cycles, and during the period that encompassed the maximum intensity for each storm. The strike density (number of strikes per (100 km)2) ratio between the eyewall region (0 - 50 km) and the outer rainband region (175 - 300 km) was 6: I for Hurricane Rita, and I: I for Hurricane Katrina. This result is in contrast to those of previous remote lightning studies, which found that outer rainbands dominated the lightning distribution. The differences are shown to be at least in part the result of the more limited range of the National Lightning Detection Network (NLDN) data. Within the effective range of the aircraft radar, maxima in eyewall strike density were collocated with maxima in radar reflectivity. High lightning strike rates were also reliably associated with TRMM low brightness temperatures and large Precipitation Ice Concentration (PIC) product The differences in storm structure and lightning strike morphology between Hurricanes Rita and Katrina are documented. The implications of the results for the use of LLDN lightning data to remotely examine changes in hurricane intensity and structural evolution are discussed.