A Multi-Faceted Examination of the Extratropical Transition of Tropical Cyclones
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Transcript of A Multi-Faceted Examination of the Extratropical Transition of Tropical Cyclones
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 °