Lightning activity in the Hurricane Otis (2023) by GLM

Hurricanes are arguably Earth's most dangerous meteorological phenomena, frequently causing tremendous devastation, particularly when their landfall is in a densely populated region. For example, Hurricane Otis' landfall near Acapulco as a Category 5 caused significant destruction with infrastructure total damage estimated between 3.5 and 15 billion US dollars (Moody 2023) and loss of human life (at least 51 people, Associated Press 2023). Hurricane Otis is the second most extreme Rapid intensification (RI, intensification rate higher than the threshold of +30 kn in 24 hours) process in the Eastern Pacific basin. We use the total lightning data obtained from the Geostationary Lightning Mapper (GLM) to investigate the lightning activity in Otis along its track and its different regions (e.g., Eyewall, Inner Rain Band, and Rain Band). Using data from the International Best Track Archive (IBTrACS), we determined the category (date and hour) and the coordinates of the storm center by way of the lightning activity analysis.

Studies previously indicated that total lightning measurements (e.g., lightning density (strikes per unit area and time) and the total count of flashes (strikes per time)) would provide the most information concerning the convective evolution and related intensity and structure changes of tropical cyclones. We found that in the eyewall region (0–50 km from the hurricane center) the maximum total count of flashes (409 strikes 5min^-1) occurred when Otis became Category 5 (25 October 2023 0300 UTC). This value is greater than that reported in Hurricane Maria (2017) by Fierro et al. (2018) (150 strikes 5min^-1). However, during the category Tropical Storm (24 October 2023 0600 UTC), we found the maximum number of flashes in the Inner rain band (75–175 km) and Rain band (200–300 km), 160 strikes 5min^-1 and 384 strikes 5min^-1, respectively. This first (second) value was less (identical) than reported in similar regions of Hurricane Maria (2017) by Fierro et al. (2018) (383 strikes 5min^-1).

Concerning lightning density, we found the maximum value of data for the eyewall region (10.194 strikes 10km^-2 5min^-1 during Category 5), for the Inner rain band (3.206 strikes 10km^-2 5min^-1 during Category Tropical Storm), and for the Rain band (6.168 strikes 10km^-2 5min^-1 during Category Tropical Storm). These values were less than those reported by Duran et al., 2021 during Hurricane Dorian (2019); they counted 23.33 strikes 10km^-2 5min^-1 for the eyewall and 18.33 strikes 10km^-2 5min^-1 for the Rain band.

The difference between our results and previous studies likely is the result of the amounts of precipitation-sized ice, cloud ice, and intensity of updrafts; which are factors that play an important role in the lightning occurrence.