18B.1 The Morphology of Eyewall Lightning Outbreaks in Two Category Five Hurricanes (2008

18B.1

The Morphology of Eyewall Lightning Outbreaks in Two Category Five Hurricanes

Kirt A. Squires, NOAA/NWS, Ronkonkoma, NY; and S. Businger

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.