Case Study of the 6–7 September Eyewall Replacement Cycle in Hurricane Irma (2017)

Hurricane Irma was one of the most impressive storms of the 2017 Atlantic hurricane season, not only in terms of its maximum wind speed, but also for the large radial extent of its wind field. In order to attain such a large wind field, Irma underwent multiple eyewall replacement cycles (ERCs) during its lifetime. Understanding the physical, dynamical, and structural changes that occur in tropical cyclone (TCs) that undergo ERCs is vital to correctly forecasting the overall intensity and area potentially affected by the TC. Irma’s ERC of 6–7 September was chosen to study because there were multiple aircraft flights during the ERC, the event was captured on the Puerto Rico WSR-88D radar, and because the hurricane was at a large enough distance from a major continent that land and aerosols would not distort the TC’s lightning signatures.

This research attempts to show how well Irma’s ERC compares to what theory predicts should occur in a TC undergoing an ERC. Additionally this research uses the World Wide Lightning Location Network (WWLLN) to create plots of storm centered cloud-ground lightning strikes. These plots are used to determine the evolution of lightning occurrences in a TC undergoing an ERC.