May 22 - July 30
Identifying Critical Strengths and Limitations of Current Radar Systems
Patrick George, Kristin Calhoun, and Ben Schenkel
What is already known:
- Inner core lightning bursts (ICLBs) correlate with tropical cyclone intensification and weakening (e.g., Stevenson et al. 2018).
- ICLBs within 1.5 to 2 times the radius of maximum wind (RMW) are indicative of intensification, while ICLBs outside the RMW threshold signify weakening.
- The RMW typically contracts (expands) as tropical cyclones intensify (weaken).
- The arrangement of symmetrical (asymmetrical) convection within tropical cyclones exhibits a correlation towards intensification (weakening).
What this study adds:
- Inner core lightning bursts in Milton consisted of small flashes, with the smallest flashes correlating to times of rapid intensification. Lightning in the rainbands outside of the RMW typically consisted of larger flashes.
- Parallel contractions of lightning and the RMW occurred during periods of peak intensity, with the smallest radius for each occurring when Milton had its lowest pressure of 895 mb.
- GLM lightning flashes fully saturated the inner core for more than 12 hours as convective elements strengthened during the initial rapid intensification to Category 5. Following a general weakening during an eyewall replacement cycle, another ICLB occurred – lasting approximately 18 hours as Milton re-intensified to a Category 5 storm.
- Asymmetric patterns were evident as Milton approached landfall on the west coast of Florida, where it weakened due to increased shear in the area. The highest lightning flash rates occurred at this time across central Florida, associated with the rainbands and embedded tornadic supercell storms.
Abstract:
This study aims to investigate the correlation between lightning activity and intensity changes in Hurricane Milton (2024). Geostationary Lightning Mapper (GLM) data was used to analyze lightning flash event counts and area in relation to the tropical cyclones minimum central pressure and structural evolution. Inner core lightning bursts were analyzed within two to three times the radius of maximum wind (RMW). Various stages of Hurricane Milton’s lifetime were analyzed, including before rapid intensification, rapid intensification, the eyewall replacement cycle, re-intensification, and landfall. Resemblance to other major hurricanes studied in similar works was found; inner core lightning bursts were an indication of rapid intensification in Hurricane Milton. There was parallel contraction of lightning and the RMW during peak intensity, and during periods of contraction, when Hurricane Milton was at its strongest, flash size tended to decrease. Additionally, the symmetrical pattern during intensification is an indicator that convective elements wrap around the eyewall in the inner core. Asymmetry indicates a weakening of Hurricane Milton influenced by shear and other factors. During the eye wall replacement cycle the lightning activity patterns of the eye wall replacement cycle is present.