Shuyi S. ChenJoseph Tenerelli

Rosenstiel School of Marine and Atmospheric ScienceUniversity of Miami

Effects of Environmental Flow and Initial Vortex on Eyewall Replacements in Tropical Cyclones

2004 Western Pacific Geophysics Meeting, Honolulu, 16-20 August

NOAA/HRD&AOC Radar Composites in Hurricane Isabel (2003)

9/12/03 1700 UTC 9/12/03 2000 UTC 9/13/03 1600 UTC

9/13/03 1800 UTC 9/14/03 1600 UTC 9/14/03 2000 UTC

NOAA/HRD&AOC Radar Composites in Hurricane Lili (2002)

10/02 0600

10/02 0900

10/02 1800

10/02 1900

10/02 1700

10/03 1500

Hurricane Floyd (1999)

MM5

Hurricane Floyd (1999)

Isabel (2003) Floyd (1999)

Isabel (2003) Floyd (1999)

What are the impacts of initial vortex size on intensity, inner core structure and eyewall cycles of simulated tropical cyclones?

Model Configuration

• Eliminate land; set terrain height to zero.

• Set SST to constant 303 K.

• Turn off shortwave radiation.

• Retain longwave radiation.

• Fix Coriolis force at 5x10-5 s-1.

• Eliminate curvature terms.

• Set the map scale factor to unity.

Surface Rain Rate

Moist Potential Vorticity

What is the influence of environmental flow on the inner core structure and eyewall cycles of simulated tropical cyclones?

• Moisture• Vertical wind shear

Mean RH Profiles

Derek and Chen (2004):NOAA/G-IV GPS dropsondes (49 flights and 1002 dropsondes, mostly taken in the TC environment outside of 300 km radius from TC centers)

Intensity

(a) pressure (b) wind speed

Chen&Desflots (UM/RSMAS)

Chen&Desflots (UM/RSMAS)

Chen&Desflots (UM/RSMAS)

Eyewall Evolution in Lili (2002)pressure

Shear Analysis in Lili (2002)

SLP : 943.9mbSHEAR:0.55m/s

SLP : 943.9mbSHEAR:2.8m/s

SLP : 944.4mbSHEAR:4.4m/s

SLP : 948.9mbSHEAR:7m/s

SLP : 953.1mbSHEAR:9m/s

SLP : 955.1mbSHEAR:9.2m/s

RainfallMoist simulationControl runDry simulation

Conclusions• Initial vortex structure seems to have a significant

influence on the evolution of TC inner core and eyewall replacements .

• Minimum SLP is only weakly dependent upon initial vortex size, whereas maximum wind speed exhibits some variability between runs, with higher speeds for smaller vortices.

• Influence of environmental moisture distribution and vertical wind shear on eyewall cycles is complex and storm-dependent.

Questions: Are we any better in predicting TCintensity changes than a decade ago?Yes, ……but, …….