Lightning distribution and eyewall outbreaks in tropical cyclones during landfall

Abstract

Cloud-to-ground lightning data and storm intensity data (winds and central pressure) for 33 northwest Pacific tropical cyclones were used to analyze lightning distributions during the period of landfall in China. Lightning activities varied enormously fromstorm to storm with an average flash rate over 500 kmof radius from 3 to 3201 flashes per hour, and no obvious relationship between average intensity and average flash rate occurred. The maximum flash density shifted from the eyewall region (0-60 km) to outer rainbands (180-500 km) as the intensity level increased. The average ratio of flash density in the eyewall to outer rainband was highest (1:0. 5) for storms with the level of a tropical storm (17. 2-24. 4 m s-1) and lowest (1:8. 6) for severe typhoons (41. 5-50. 9 m s-1). After storm landfall, flash density in the rainband decreased more rapidly in severe typhoons than in severe tropical storms (24. 5-32. 6 m s-1) and typhoons, but increased in tropical depressions (10. 8-17. 1 m s-1) and tropical storms. With the strength of intensity level, lightning in the outer rainband gradually weakened after the storm landfall. Lightning outbreaks were identified in a consistent manner for all tropical cyclones to inspect the relationship of eyewall flashes to the changes of structure and intensity. Eyewall flash outbreaks were found during the period of intensity change (15% of outbreaks in intensification and 43% in weaken), and the period of maximum intensity (15% of outbreaks) of storms. A new result of this analysis found that 10% of the outbreaks occurred prior to and during periods of storm turning, which is potentially important for the trajectory change forecasting of tropical cyclones. ©2012 American Meteorological Society.