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.

Four characteristic tropical cyclone rainband/eyewall structures

In the convective rainband region outside of the hurricane inner core, convectively induced potential vorticity may be “axisymmetrized” by high wave number Rossby waves.

Working hypothesis, based on recent research:

1) How do PV maxima associated with rainbands organize (axisymmetrize) into the primary eyewall?

2) How do PV maxima associated with rainbands outside the primary eyewall interact with the eyewall?

3) How do PV maxima associated with rainbands outside the primary eyewall axisymmetrize into a secondary eyewall

4) How do the secondary and primary eyewall interact with each other

Specific questions

Objectives

Use a/c to examine the dynamic and thermodynamic structures of hurricane outer rainband regions where the positive potential vorticity associated with deep convective cores are located

Use model to investigate the interactions of the rainbands and primary hurricane vortex circulation and their role in hurricane intensity change.

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

Approach:

Hurricane Floyd (1999)

12 Sep 2230-2300 UTC 13 Sep 2300-2330 UTC

RAINEX A/C Plan

Isabel 2003

End

Courtesy, Hugh Willoughby

For structures:

Use airborne dual-Doppler radar

For interactions:

Use University of Miami coupled model (MM5-WW3-HYCOM)

Approach