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

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

Upper Air Analysis - 1200 UTC 19 July 2006

250 mb analysis 500 mb analysis

Upper Air Analysis - 1200 UTC 19 July 2006

850 mb analysis RUC 700-500 mb lapse rate (°C km-1)

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

Radar Imagery Composites and 06z SPC Outlook

Composite base reflectivity 1210 UTC

SPC radar animation1200-1315 UTC

Radar Imagery Composites and 13z SPC Outlook

Composite base reflectivity 1610 UTC

SPC radar animation1454-1615 UTC

Hourly MCS Track and Storm Reports

1800 UTC Surface Analysis 19 July 2006

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

Winchester, IL (WNC) Profiler 1700 - 2200 UTC

17 18 19 20 21 22

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

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

Parker’s Study on Linear MCS archetypes

The 19 July 2006 Damaging Wind Convective system followed theParallel Stratiform (PS) archetype

WSR-88D Radar Imageryfrom Lincoln Illinois (KILX)at 2138 UTC

Parallel Stratiform Parker and Johnson 2000

Conceptual model of a multicell cluster storm complex.(NSSL)

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

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!

Loop of the evolution of a single severe cell over the western part of the storm complex.

ASOS / AWOS Surface Observation sites around the GreaterSt. Louis metro area.

Bunker Hill

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.

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.

Tower Grove Park

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 )

- 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.