Tuesday, 24 January 2012: 3:30 PM
Strucutre of Mesovortices in Hurricane Ike (2008) Derived From Dual-Doppler Analyses From Ground-Based Radars
Room 338 (New Orleans Convention Center )
Past modeling work has shown that vorticity mixing in the tropical cyclone (TC) inner core can lead to mesovortices (MVs) and impact storm intensity. Observations of MVs are necessary to improve understanding of these features and their role in TC dynamics, but few have been made. This study presents nearly 10 hr of observation of MVs in the inner eyewall of Hurricane Ike (2008) prior to and during landfall. Dual-Doppler derived vertical vorticity, divergence, perturbation pressure, horizontal and vertical wind fields are analyzed over the landfall time period. Results indicate persistent arrangements in kinematic fields that degrade as the hurricane progresses inland. Perturbation pressure retrievals suggest a local pressure minimum associated with mature MVs. As the entities progress around the eye, the preferential updraft location transitions around the vorticity center in a manner consistent with the conceptual model proposed by Braun et al. 2006 based on their high-resolution simulation of Hurricane Bonnie (1998). Ike's MV updraft magnitudes are within the top 5-10 % of TC vertical velocities found in previous observational studies. Characteristics shown for the MVs in Ike compare well with the limited body of previous MV observational work, including the cases of Hurricanes Hugo (1989) and Isabel (2003).