Observational and Modeling Study of Hurricane Rainbands and Intensity Changes aka

1. Observational and Modeling Study of Hurricane Rainbands and Intensity Changes aka Rainband and Intensity Change Experiment “RAINEX” Shuyi S. Chen and Robert A. Houze, Jr.

2. Four characteristic tropical cyclone rainband/eyewall structures

3. Working hypothesis, based on recent research: In the convective rainband region outside of the hurricane inner core, convectively induced potential vorticity may be “axisymmetrized” by high wave number Rossby waves.

4. Specific questions • How do PV maxima associated with rainbands organize (axisymmetrize) into the primary eyewall? • How do PV maxima associated with rainbands outside the primary eyewall interact with the eyewall? • How do PV maxima associated with rainbands outside the primary eyewall axisymmetrize into a secondary eyewall • How do the secondary and primary eyewall interact with each other

5. Objectives • Use a/c to examine the dynamic and thermodynamic structuresof hurricane outer rainband regions where the positive potential vorticity associated with deep convective cores are located • Use model to investigate the interactionsof the rainbands and primary hurricane vortex circulation and their role in hurricane intensity change.

6. Approach: Use a/c to observe both eyewall and rainband vorticity structures simultaneously Seek match between model and a/c observed structures at an instant of time, in both eyewall and rainband Use model to determine how the vorticity features evolve and storm intensity changes

7. Hurricane Floyd (1999) 12 Sep 2230-2300 UTC 13 Sep 2300-2330 UTC

10. RAINEX A/C Plan

11. Isabel 2003

13. End

15. Courtesy, Hugh Willoughby

17. Approach • For structures: • Use airborne dual-Doppler radar • For interactions: • Use University of Miami coupled model (MM5-WW3-HYCOM)