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19 July 2006 Derecho:A Meteorological Perspective and
Lessons Learned from this Event
Ron W. Przybylinski, James E. Sieveking, Benjamin D. Sipprell
NOAA / National Weather Service St. Louis
Jared L. GuyerNOAA/NWS/NCEP Storm Prediction Center
2009 Spring Media Workshop
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Outline of this Presentation
• Synoptic scale conditions the morning of 19 July 2006
• Storm overview (large scale perspective) • Mesoscale Environment during the afternoon of
19 July 2006 over southern Iowa, Missouri and Illinois.
• WSR-88D Doppler radar analysis of the storm complex from WFO Lincoln Illinois and WFO St. Louis perspectives.
• Some final comments
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Upper Air Analysis - 1200 UTC 19 July 2006
250 mb analysis 500 mb analysis
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Upper Air Analysis - 1200 UTC 19 July 2006
850 mb analysis RUC 700-500 mb lapse rate (°C km-1)
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1200 UTC DVN Observed Raob
MLCAPE MUCAPE 700-500 LR 0-6 km Shear 0-3 km Shear
1333 J kg-1 2855 J kg-1 7.4 °C km-1 14 m s-1 6 m s-1
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Radar Imagery Composites and 06z SPC Outlook
Composite base reflectivity 1210 UTC
SPC radar animation1200-1315 UTC
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Radar Imagery Composites and 13z SPC Outlook
Composite base reflectivity 1610 UTC
SPC radar animation1454-1615 UTC
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Hourly MCS Track and Storm Reports
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1800 UTC Surface Analysis 19 July 2006
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RUC 00-hr Sounding for SPI at 2100 UTC
MLCAPE MUCAPE 700-500 LR 0-6 km Shear 0-3 km Shear
5392 J kg-1 6065 J kg-1 7.3 °C km-1 11 m s-1 8 m s-1
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Winchester, IL (WNC) Profiler 1700 - 2200 UTC
17 18 19 20 21 22
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SPC Mesoscale analysis for MLCAPE and 0-6 km bulk shear at 2300 UTC
MLCAPE ranged from 2000 – 6000 J kg-1 acrosseastern Missouri through
west-central Illinois
Deep layer shear weak with magnitudes of
10 – 22 m s-1
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RUC 00-hr Sounding for STL at 2300 UTC
MLCAPE MUCAPE 700-500 LR 0-6 km Shear 0-3 km Shear
2882 J kg-1 2954 J kg-1 7.4 °C km-1 12 m s-1 6 m s-1
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Parker’s Study on Linear MCS archetypes
The 19 July 2006 Damaging Wind Convective system followed theParallel Stratiform (PS) archetype
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WSR-88D Radar Imageryfrom Lincoln Illinois (KILX)at 2138 UTC
Parallel Stratiform Parker and Johnson 2000
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Conceptual model of a multicell cluster storm complex.(NSSL)
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2332 UTC Radar imagery from St. Louis (KLSX). The strongest winds were associated with convective segment #3 (larger echo mass).
Several witnesses over southern Macoupin County experience hail up to nickel size with the stronger downbursts behind the leading gust front.
KLSX radar imagery for 2332 UTC
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7:01 PM CDT Reflectivity (left), Base velocity (right). The strongest winds were detected with the higher reflectivity cores over northwest Madison County Illinois.
I Was Here!I Was Here!
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Loop of the evolution of a single severe cell over the western part of the storm complex.
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ASOS / AWOS Surface Observation sites around the GreaterSt. Louis metro area.
Bunker Hill
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When was the last time we documented a case similarto the July 19, 2006 Derecho?
Aug 10, 1992. The convective complex formed just southwest of KLSXand moved south-southward through west-central Arkansas. Widespread wind damage occurred with this derecho.
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The July 19 2006 damage map reveals that much of the downbursts was oriented from north-northeast to south-southwest – an unusual direction.This direction of damaging winds future intensified the degree of damage over the greater St. Louis metro area.
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Tower Grove Park
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Summary - On 19 July 2006 formed over northeast Iowa and causedsevere wind damage from parts of northeast Iowa through central Illinois and then south-southwest across the Greater St. Louis metro area and then into southwest Missouri.(A typical movement).
- Over 500,000 people were without power from this windstorm. The oppressive HEAT AND HUMIDTY after this event brought suffering to a large part of the population.
- The environment over the Mid-Mississippi Valley regionwas extremely unstable with ML CAPEs of 2600 to 6000 J/Kg while a deep layer shear was weak (< 22 m s-1 )
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- RUC sounding at 2300 UTC from STL showed a very weak cap.
- The upper-level ridge over the central plains built eastwardinto Illinois allowing the MCS to move in a south-southwestdirection during the late afternoon and evening.
- The overall storm morphology took on the characteristics of “parallel stratiform” type system where three convective segments showed “pulse – multicellular” characteristics.
- Convective segment #3 (eastern most storm) was themost consistent storm complex of the three groups.
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- Surface winds along the leading edge of the gustfront varied between 20 to 31 m s-1.
- The strongest surface winds were associated with the isolated convective towers through the area of mature convection. Wind speed estimates – 40 m s-1
- This wind storm was one of the more challenging cases, from both a national and local WFO perspective.