Evolution of Hurricane Isabel’s (2003) Vortex Structure and Intensity

http://www.nhc.noaa.gov

Peter J. KozichMPO/RSMAS/UMFebruary 23, 2005

MOTIVATIONMOTIVATION

Tropical cyclone (TC) dynamic and thermodynamic fields have been well documented by airborne measurements and numerical simulation (e.g., Shea and Gray 1973, Liu et al. 1997, Marks 2003). However, understanding and predicting evolution of TC structure and intensity remains a challenge.

Investigation focuses on time frame between dotted lines

Selected model times in green, best track in black

9/14 1822-1852 UTC 9/14 2157-2222 UTC9/13 1915-1945 UTC

9/13 1625-1650 UTC9/12 2000-2030 UTC9/12 1644-1709 UTC

NOAA-42 Reflectivity

http://www.aoml.noaa.gov/hrd/Storm_pages/isabel2003/radar.html

Analysis Time #1

Analysis Time #2

Objectives:By use of airborne radar and model data, we will aim to understand the physical processes in the inner core their effect on intensity change of Isabel (2003). Specifically:

1) Document the strom structures using airborne. Doppler radar and flight-level data from NOAA P3s.

2) Compare with high-resolution model simulation to validate/evaluate model results.

3) Diagnose model results to understand the dynamic processes (e.g., PV, angular momentum, etc.) controlling the evolution of Hurricane Isabel.

ModelModel

5th generation high resolution, non- hydrostatic PSU/NCAR mesoscale model (MM5)

Multi-nested, vortex-following domains with grid resolutions of 45, 15, 5, 1.67 km

28 vertical sigma-levels, 9 in boundary layer

Initial, lateral BC: NCEP-FNL Analysis, 1° x 1°

Lower boundary: SSM/I SST 0.25 ° x 0.25°

D02

D03

D04

MM5 Domains:

Data

Doppler radar data from horizontally scanning and vertically scanning tail radar on NOAA-HRD WP-3D 42 aircraft

Data covers period from 1644 UTC September 12th – 1903 UTC September 14th

Following the data analysis procedure described in Marks et al. (1992).

9/14 1822-1852 UTC 9/14 2157-2222 UTC9/13 1915-1945 UTC

9/13 1625-1650 UTC9/12 2000-2030 UTC9/12 1644-1709 UTC

NOAA-42 Reflectivity

http://www.aoml.noaa.gov/hrd/Storm_pages/isabel2003/radar.html

Analysis Time #1

Analysis Time #2

Winds at 2 km levelradar

MM5

Radius-height mean profiles of radar reflectivity (dBZ):

radar

MM5

Total Wind Speed (ms-1):

radar

MM5

Radial Wind Speed (ms-1):

radar

MM5

Hovmoller Diagrams:

http://orca.rsmas.miami.edu/~joe/isabel/hov/

Relative Vorticity, (x 10-3 s-1) at 2 km :

radar

MM5

x 10-3 s-1

ConclusionsConclusionsIsabel went through a distinct structural change from the 12th to the 14th as the storm weakened slightly.

The primary convective ring (eyewall) dominates on the 12th, whereas both primary and secondary rings present on the 14th that are weaker, shallower, and larger than that on the 12th.

The radial flow in the low-levels outside of RMW is better defined on 14th.

The horizontal distribution of vorticity appears to be more annular on the 14th.

Model simulated a similar structure of the storm, expect the inner core is larger than the observations.Model results indicate that Isabel went through an eyewall replacement.

Future WorkFuture Work• Continue the airborne Doppler radar and flight-level data analysis and add orthogonal flight legs on 12th and 14th, pair on the 13th.

• To work with Dr. Chen and John Cangialosi on improving the MM5 initial condition for Hurricane Isabel.

• Analyzing model simulated storm evolution and develop a concept model to understand the dynamic processes in the evolution of Hurricane Isabel (e.g., PV, heat and momentum profiles, and gradient wind profiles, etc.)

Acknowledgments:

Many thanks to Shuyi Chen, Dave Nolan, Frank Marks, Peter Dodge, Melicie Desflots, and John Cangialosi for their guidance, suggestions, and dedication.

HRD radar tapes

solo

Procedure:

wind_interpolate

wind3_fill

XLTRS

XLTRS

swp.*

ufd.*

SUMFILEs

radar_slicerFilename.w

plots

1717-1731 UTC (pink) 1625-1642 UTC (blue)

1644-1700 UTC (pink)1720-1735 UTC (blue)

9/14/03:

Flight-Level Wind Profile 9/12

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Flight Level Wind Profiles for Plotted Times:9/12/03:

Flight Level Wind Profiles 9/12 (black), 9/14 (brown)

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101520253035404550556065707580

0 20 40 60 80 100 120 140

radius (km)

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