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. Guyer NOAA/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 UTC 19 July mb analysis500 mb analysis

Upper Air Analysis UTC 19 July mb analysis RUC mb lapse rate (°C km -1 )

1200 UTC DVN Observed Raob MLCAPEMUCAPE LR0-6 km Shear0-3 km Shear 1333 J kg J kg °C km m s -1 6 m s -1

Radar Imagery Composites and 06z SPC Outlook Composite base reflectivity 1210 UTC SPC radar animation UTC

Radar Imagery Composites and 13z SPC Outlook Composite base reflectivity 1610 UTC SPC radar animation UTC

Hourly MCS Track and Storm Reports

1800 UTC Surface Analysis 19 July 2006

RUC 00-hr Sounding for SPI at 2100 UTC MLCAPEMUCAPE LR0-6 km Shear0-3 km Shear 5392 J kg J kg °C km m s -1 8 m s -1

Winchester, IL (WNC) Profiler UTC

SPC Mesoscale analysis for MLCAPE and 0-6 km bulk shear at 2300 UTC MLCAPE ranged from 2000 – 6000 J kg -1 across eastern 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 MLCAPEMUCAPE LR0-6 km Shear0-3 km Shear 2882 J kg J kg °C km m s -1 6 m s -1

Parker’s Study on Linear MCS archetypes The 19 July 2006 Damaging Wind Convective system followed the Parallel Stratiform (PS) archetype

WSR-88D Radar Imagery from 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!

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

ASOS / AWOS Surface Observation sites around the Greater St. Louis metro area. Bunker Hill

When was the last time we documented a case similar to the July 19, 2006 Derecho? Aug 10, The convective complex formed just southwest of KLSX and moved south-southward through west-central Arkansas. Widespread wind damage occurred with this derecho.

The July 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 caused severe 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 wind storm. The oppressive HEAT AND HUMIDTY after this event brought suffering to a large part of the population. - The environment over the Mid-Mississippi Valley region was 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 eastward into Illinois allowing the MCS to move in a south-southwest direction 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 the most consistent storm complex of the three groups. -

- Surface winds along the leading edge of the gust front 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.