A Multi-Faceted Examination of the Extratropical Transition

of Tropical Cyclones

Steve Guimond

ONR Intern

FSU/COAPS

Tuesday, July 19, 2005 2 pm

Overview of Extratropical Transition (ET) symmetric,warm-core,non-frontal,barotropic

GOES-12 1 km VIS

Hurricane Karl 20 Sep 2004 1215Z 17N Typhoon Sonca 25 Apr 2005 0302Z 16N

www.nnvl.noaa.gov

Overview of Extratropical Transition (ET) asymmetric,cold-core,frontal,baroclinic

GOES-12 1 km VIS GOES-9 4 km IR

Hurricane Karl 24 Sep 2004 1215Z 40N Typhoon Sonca 25 Apr 2005 0302Z 21N

www.nnvl.noaa.gov

Tracking TC Structure: Cyclone Phase Space (Dr. Robert Hart FSU)

Who Cares? Why Is This Important?

• ET can produce:

– Continuation of high winds with wind field expansion– Large ocean swell– Extreme rainfall (intensity and accumulation)– Rapid track accelerations

• Forecasting Challenges

– Predicting track,intensity and rainfall – Warning for high winds,heavy seas and flooding

• Threat to Naval operations in various sub-tropical ocean basins

How Can I Help Solve The Problem?

New Approaches to Analyzing ET

Focus: Quantitative Precipitation Forecasting (QPF)

(1) Multi-Satellite Blended Precipitation Products

(2) Mapping Cyclone Structural Phase from Satellite Perspective

(3) Algorithm to Compute CAPE from AMSU/HIRS for Convective Rainfall Predictive Purposes

Master’s Thesis

(1) Computing Moisture Budget

(2) Describing Dynamical Forcings from Phase Space

Model Moisture Evaluation: Hurricane Karl

• ECMWF 1.125° vs. NOGAPS QUASI 1.0°– Mean 400-500 hPa Relative Humidities

• Compared to GOES-12 WV(ch 3) 4 km– Weighting Function Peaks in ~400-500 hPa Layer

• Purpose: To find model that describes evolution of ET signatures more realistically

ECMWF1.125 °

NOGAPS~1.0 °

ECMWF1.125 °

NOGAPS~1.0 °

Isentropic Ertel Potential Vorticity

Hurricane Karl 2004

Explains interaction and response of TC from movement into a baroclinic environment

Isentropic Ertel Potential Vorticity Animation

Typhoon Sonca 2005

Early Season Case: Storm Sheared Apart By Sub-Tropical Jet

Multi-Satellite Blended Precipitation Products

• Buffet of Passive Microwave Sensors (“constellation”)– TRMM TMI/PR– F-13/14/15 DMSP/SSMI– NOAA-15/16/17 AMSU-B– EOS AMSR-E

• Utilize rapid time capability of geo-IR to calibrate the IR obs between gaps in constellation

Result ?• High quality precip on dense space and time scales• NASA vs. NRL: NRL smaller error!!

Blended Satellite Precipitation NRLB:Hurricane Karl

Mean 3 hourly rainrate

Blended Satellite Precipitation NRLB:Typhoon Sonca 2005

Mean 3 hourly rainrate

Precipitation Evolution Analysis Techniques

• Divide storm into annuli

• Examine mean precipitation change (intensity and accumulation) vs. time and distance from TC center

• Serve as risk assessment tool for ET precipitation enhancement and flooding

Mapping Cyclone Structural Phase:Satellite Perspective

• TRMM PR Bright Band Heights proxy for warm/cold core structure– Bright Band = distinct radar

signal created by frozen hydrometeors falling through storm melting layer

– Stratiform precipitation typically associated with convective cells

– Retrieve melting layer heights along ET track produce satellite derived cyclone phase

Test Case: Typhoon Meari 2004

• TRMM PR STATS– 4 km horizontal resolution

– 250 m vertical resolution

– 220 km swath width

– Coverage: 40°N/S

– 100 along track scans/minute

– 49 across track rays/scan

AMSU

AMSU

TRMM PR Vertical Cross Section Animation

Things to look for:

(1) Fluctuations in Convective Cloud Heights

Mirrors intensity change

(2) Development of Outer Core/Asymmetric Precipitation

ET Signature

(3) Changes to darker colors

Heavy precipitation;Higher dBZ values

Zoomed Snapshots: Two Stages of Typhoon Meari

Warm Core Cold Core

A TRMM PR STRUCTURAL TRACK

Features of CAPE algorithm

• Soundings produced from retrievals of T and Q at each pixel of AMSU/HIRS

• Mixed layer parcel – 100 hPa tropics;50 hPa mid-lats yields more accurate cloud base

heights and CAPE (Craven et al. 2002)

• Virtual temperature correction– Accounts for variable amount of moisture allowing use of dry gas

constant when calculating density

• Accounts for irregular soundings– Unrealistic tropopause levels

– Parcel acquiring negative buoyancy

Test Case: Hurricane KarlExamining Convective Precipitation

Trough approaching high

CAPE Response to CAPE

TEST CASE: Hurricane Karl

Potential for convective forecasting over various ocean basins and regions with sparse radiosonde networks

TC Genesis Studies

What to Take Away From this Seminar

• Multi-satellite blended precipitation products useful for QPF studies– Explain ET rainfall enhancement

– Blazing Trails: Never been done before with ET

• Objective satellite cyclone phase– Shown to distinguish ET commencment from warm to cold

core

– Promise for future work

• CAPE algorithm useful for convective precipitation forecasting– AMSU/HIRS derived soundings need work in upper levels

MANY,MANY THANKS TO

• Jeff Hawkins – Support for Internship;Insightful comments;Food and Beverage

(pumpkin bread)

• Joe Turk– Extensive knowledge of satellite precipitation;Making me spend 3+

hours retrieving TRMM data

• Clay Blankenship and Ben Ruston– Retrievals for CAPE;support for coding issues

• Kim Richardson– Computer assistance and book loans

• Rob Wade– NOGAPS and GOES WV data

Everyone who made my stay an enjoyable one!

Thanks to Tom Lee for BIG SUR TRIP

ECMWF1.125 °

NOGAPS~1.0 °

ECMWF1.125 °

NOGAPS~1.0 °

ECMWF1.125 °

NOGAPS~1.0 °