Tropical Cyclone Intensity Changes Associated with Outer Rainband Lightning

Recent studies have found that increased lightning activity in the outer rainbands is associated with tropical cyclone (TC) intensification; however, a scientific understanding of why this association occurs is unknown. One study hypothesized that more lightning activity in the outer rainbands was a signal that the TC was moving into a more favorable environment, while another suggested that positive potential vorticity anomalies, diabatically-generated by outer rainband convection, could be advected toward the TC core. However, previous modeling and theoretical work has argued that stronger convection in the outer rainbands inhibits intensification by: 1) reducing the mass convergence in the eyewall, 2) inducing compensating subsidence in the eyewall convection, 3) fluxing cool, dry air into the boundary layer inflow from convective-scale downdrafts, and 4) hydrostatically reducing the radial pressure gradient.

This study will utilize data in eastern North Pacific and North Atlantic TCs from the World Wide Lightning Location Network (WWLLN) between 2005 and 2014 to better understand the impacts of electrically-active outer rainbands. A climatology of electrically-active deep convection in the outer rainbands (150–300 km) is created. The kinematic and thermodynamic impacts of these rainbands identified in the climatology are investigated using observations from recent NASA field campaigns (GRIP: Genesis and Rapid Intensification Processes, and HS3: Hurricane and Severe Storm Sentinel).