11 March 2000 Snowstorm Overview

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Case Study Overview of the 11 March 2000 Snow
Event Over Central and Southeastern
Missouri Marc J. Singer and James T.
Moore Cooperative Institute for Precipitation
Systems Saint Louis University Department of
Earth Atmospheric Sciences COMET-RFC/HPC
Hydrometeorology Course 01-1 14-21 November 2000
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METAR Reports 11 UTC to 01 UTC for STL
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Snowfall amounts ending 18 UTC 11 March 2000
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Figure from Nicosia and Grumm (1999). Zone of
EPV reduction occurs where the mid-level dry
tongue jet overlays the low-level easterly jet
(or cold conveyor belt), north of the surface
low. In this area dry air at mid-levels overruns
moisture-laden low-level easterly flow, thereby
steepening the slope of the ?e surfaces.
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Infrared Satellite Imagery Valid 0115 UTC to 2315
UTC 11 March 2000
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Water Vapor Satellite Imagery Valid 0115 UTC to
2315 UTC 11 March 2000
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500 mb heights 00 UTC 11 March 2000
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294 K Streamlines and Pressure 00 UTC 11 March
2000
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294 K Omega 00 UTC 11 March 2000
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294 K System Relative Streamlines and Pressure
00 UTC 11 March 2000
C 331.3 at 7.6 m/s
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294 K System Relative Omega 00 UTC 11 March 2000
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294 K Moisture Transport Vectors 00 UTC 11
March 2000
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294 K System Relative Moisture Transport Vectors
00 UTC 11 March 2000
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500 mb heights 12 UTC 11 March 2000
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294 K Streamlines and Pressure 12 UTC 11 March
2000
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294 K Omega 12 UTC 11 March 2000
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294 K System Relative Streamlines and Pressure
12 UTC 11 March 2000
C 276.3 at 14.0 m/s
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294 K System Relative Omega 12 UTC 11 March 2000
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294 K Moisture Transport Vectors 12 UTC 11 March
2000
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294 K System Relative Moisture Transport Vectors
12 UTC 11 March 2000
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Model QPF for 0-6 hours
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Model QPF for 6-12 hours
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Model QPF for 12-18 hours
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800 - 700 Frontogenesis Valid 6 hours
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800 - 700 Frontogenesis Valid 12 hours
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800 - 700 Frontogenesis Valid 18 hours
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Cross Section Taken to Evaluate Ageostrophic
Circulations and CSI
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Cross Section of Tangential Ageostrophic Winds /
Vertical Motion
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Cross Section of Mg Surfaces and ?e Surfaces to
Evaluate Conditional Symmetric Instability
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Cross Section of Relative Humidity
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850 mb Temperature / MSLP Valid 6 hrs
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850 mb Temperature / MSLP Valid 12 hrs
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1000 / 500 Layer Mean Relative Humidity Valid 6
hrs
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1000 / 500 Layer Mean Relative Humidity Valid 12
hrs
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294 K Surface System Relative Winds Valid 6 hrs
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294 K Surface System Relative Isentropic Lift
Valid 6 hrs
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294 K Surface System Relative Winds Valid 12 hrs
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294 K Surface System Relative Isentropic Lift
Valid 12 hrs
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324 K Surface Valid 6 hrs
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324 K Surface Valid 12 hrs
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Cloud-Ground Lightning Flashes 9-10 UTC 11 March
2000 Courtesy of Phil Bothwell
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Cloud-Ground Lightning Flashes 10-11 UTC 11 March
2000 Courtesy of Phil Bothwell
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Cloud-Ground Lightning Flashes 11-12 UTC 11 March
2000 Courtesy of Phil Bothwell
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Cloud-Ground Lightning Flashes 12-13 UTC 11 March
2000 Courtesy of Phil Bothwell
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Cloud-Ground Lightning Flashes 13-14 UTC 11 March
2000 Courtesy of Phil Bothwell
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Conclusions

• Snow developed in a region characterized by
• High mean RH
• Moderate isentropic system-relative uplift
• Marginal amounts of CAPE (lt100 J kg-1)
• mid-level frontogenesis and DTC
• Coupled upper-level jet streak structure
• Decrease in half-wavelength between trough and
  downstream ridge
• Dry slot seen on water vapor imagery moves into
  east-central MO appears to have destabilized
  region enough to create elevated thunderstorms
  which dramatically enhanced snow totals