An Extreme Event in the Eyewall of Hurricane Felix

On September 2, 2007, a NOAA P3 Aircraft penetrated one of the most rapidly intensifying hurricanes on record: Hurricane Felix. The mission had to be terminated due to intense turbulence as a consequence of severe horizontal and vertical winds; however, valuable data were obtained from the flight. The objective of this research is study the kinematic and thermodynamic structure of the eyewall of Hurricane Felix through analyzing the flight-level and dropsonde data in comparison with the data acquired from Hurricane Hugo (1989) in which the P3 aircraft experienced an extreme event as well. In the data analysis, the flight–level thermodynamic data error that is often caused by wetting of sensors is firstly corrected as part of quality-control. Flight-level data was plotted in a storm-relative framework, and vorticity and divergence were calculated to detect the presence of mesovortices in the eyewall of Hurricane Felix. The time evolution of pressure and wind were plotted to recognize trochoidal motion of the circulation centers. Furthermore, perturbations of wind velocities, pressure and vorticity were calculated to investigate coherent features in a similar manner as in the Hugo data analysis. Additional data such as that from dropwindsondes and the Stepped Frequency Microwave Radiometer (SFMR) were also analyzed. The results from Hurricane Felix are compared to those from Hurricane Hugo from recent study by Marks et al. (2006). Preliminary results showed very different eyewall structures between the inbound and outbound legs of Hurricane Felix. Much stronger peak winds perturbations were observed in the inbound leg in contrast with the outbound leg. Similar to Hurricane Hugo, Hurricane Felix showed recognizable trochoidal motion between the wind and pressure centers although not so pronounced as in Hurricane Hugo, maybe since the aircraft spent less time in the eye gathering data in Felix than in Hugo. This research will be continued in order to contribute to NOAA's goal in the reduction of devastating impacts caused by extreme events like hurricanes. It can be use to improve scientific understanding and forecast reliability to assess future model improvements.