The lightning flash density displays a consistent relationship with the TRMM Precipitation Ice Concentration (PIC) product. Large lightning flash rates are reliably associated with large PIC. Both storms exhibit secondary eyewall lightning outbreaks surrounding the time of maximum intensity. The period of elevated flash density for each storm lasted for 8 to 9 h centered on the time of minimum sea- level pressure. These prolonged outbreaks occurred at a time when each hurricane eye had contracted to a relatively small size and the eyewall was steep sided.
Maxima in eyewall flash density were collocated with maxima in flight-level radar reflectivity. However, flash density maxima and radar reflectivity maxima are not always collocated with minimums in brightness temperatures and high PIC. Observed spatial displacement between the location of lightning and PIC maxima can be attributed to vertical shear of the horizontal winds over the area of convection. It was observed that PIC maxima are located up-flow of convective cores that rotate cyclonically around the storm center, and down flow of convective cores that are stationary relative to the storm center. The greatest hourly flash density was not produced by the deepest convection during each storm.
The relationship of the eyewall lightning outbreaks to the evolution of the eyewall convection and the morphology of the electro-magnetic dipole will be discussed. Implications of the results for better understanding hurricane evolution through the application of long- range lightning data will be presented.