The Morphology of Eyewall Lightning Outbreaks in Two Category 5 Hurricanes

Abstract

Data from the Long-Range Lightning Detection Network (LLDN), the Tropical Rainfall Measuring Mission (TRMM) satellite, and reconnaissance aircraft are used to analyze the morphology of lightning outbreaks in the eyewalls of Hurricanes Rita and Katrina, two of the strongest storms in the Atlantic hurricane record. Each hurricane produced eyewall lightning outbreaks during the period of most rapid intensification, during eyewall replacement cycles, and during the time period that encompassed the maximum intensity for each storm. 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 consistently associated with TRMM low brightness temperatures and large precipitation ice concentration (PIC) values. The strike density ratio between the eyewall region and the outer rainband region was 6:1 for Hurricane Rita and 1:1 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 used in the earlier studies. Finally, implications of the results for the use of LLDN lightning data to remotely examine changes in hurricane intensity and structural evolution are discussed.