Improving the Validation and Prediction of Tropical Cyclone Rainfall

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Improving the Validation and Prediction of
Tropical Cyclone Rainfall

• Timothy P. Marchok
• NOAA/GFDL Princeton, NJ
• Robert F. Rogers
• NOAA/AOML/HRD Miami, FL
• Robert E. Tuleya
• NOAA/NCEP/EMC/SAIC Camp Springs, MD
• 58th Interdepartmental Hurricane Conference,
  Charleston, SC
• March 1-5, 2004
• This project is being funded by the Joint
  Hurricane Testbed (JHT)

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Goals

• Goal Develop a set of rainfall validation
  schemes more suited specifically for TCs
• Motivation Conventional precip skill scores are
  often difficult to interpret in the context of
  tropical cyclones
• Goal Produce model QPF error statistics for
  historic U.S. landfalling storms.
• Motivation No systematic QPF verification has
  been done on NWS operational models for the
  specific subset of landfalling U.S. tropical
  cyclones
• Goal Develop a modified R-CLIPER that
  incorporates vertical shear storm track
  data.
• Motivation Recent research has shown that
  including vertical shear information can add
  structure to R-CLIPER's currently symmetric
  rainfall distribution

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Outline

• Standard QPF verifications
• GFDL model 1995-2002 storms rain gauge data
• NWS operational suite 1998-2003 storms Stage IV
  gridded rainfall analyses
• Application of a new verification technique to
  Hurricane Isabels landfall
• Future work

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GFDL Model QPF Verification, 1995-2002

• Verification data Hourly daily rain gauges
• Gauge data within 800 km of storm track was
  summed over model forecast interval
• Interpolated model storm total rainfall to gauge
  location
• Average of 211 hourly gauges per storm
• Nearly 1200 daily gauges per storm
• Only used forecasts initialized at 12 UTC, to
  coincide with daily rain gauge network
• All storms within 24h of landfall

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U.S. Landfalling Cases for Model Evaluation
NWS Operational Suite
GFDL, R-CLIPER
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QPF Bias Scores GFDL vs. R-CLIPER
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Equitable Threat Scores
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Model vs. obs correlation A first guess at
pattern matching
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Track error lt-gt QPF error
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Storm Intensity lt-gt QPF Error
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QPF verification for NWS model suite 28 storms
from 1998-2003

• GFDL, NCEP/GFS, NCEP/Eta, R-CLIPER, 2xR-CLIPER
• GFDL 2003 version used for all 28 cases
• Obs data Hourly multi-sensor (radar, gauge)
  gridded data available online from NCAR
• 2002-2003 NCEP/EMC Stage IV data
• 1998-2001 NCEP/EMC Stage II data

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QPF Bias Scores
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QPF Equitable Threat Scores
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GFS 0.65 Eta 0.56 GFDL 0.52 RCLIP
0.47
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GFS 0.65 Eta 0.56 GFDL 0.52 RCLIP
0.47
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GFDL
Stage
IV
GFS
Eta
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GFDL
Stage
IV
GFS
Eta
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Rainfall statistics for observations and
forecasts of 24-h rain from 12 UTC 18 to 12 UTC
19 September for Isabel (2003)
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Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC
19 September for Isabel (2003) for NPVU and
R-CLIPER
Stage IV
R-CLIPER
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Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC
19 September for Isabel (2003) for NPVU and GFDL
Stage IV
GFDL
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Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC
19 September for Isabel (2003) for NPVU and GFS
Stage IV
GFS
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Plot of 24-h rain (in) from 12 UTC 18 to 12 UTC
19 September for Isabel (2003) for NPVU and Eta
Stage IV
Eta
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Probability-matched 24-h rain estimates from
Stage IV data vs. R-CLIPER, GFDL, GFS, and Eta
models for Hurricane Isabel
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90
90
10
10
10
10
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Summary Future Plans

• QPF error stats for landfalling TCs
• GFDL only 1995-2002 vs. rain gauge data
• NWS suite 1998-2003 vs. gridded Stage IV data
• Compare operational GFDL vs. 2003 GFDL for all
  storms, 1995-2003
• Development of a set of QPF verification schemes
  more suited to TCs
• Apply a PDF/CDF method to TC rain flux
• Use PDF/CDF method on NWS suite, 1998-2003
• Investigate other spatial-based methods?
• Develop a modified R-CLIPER that incorporates
  vertical shear storm track data (Year 2)