August 5th, 2008 Damaging Wind Event

 

From mid afternoon through the evening hours on August 5th, 2008, a Mesoscale Convective System (MCS) formed over parts of northeast Missouri and moved southeast into Lincoln county (Missouri) then crossed the Mississippi river into Illinois.  From there it traveled across parts of southwest Illinois. This convective system was responsible for the production of a large swath of damaging winds with embedded microbursts. The stronger winds were associated with the microbursts.  The damage area began over eastern Lincoln county and then moved nearly eastward across the Mississippi and Illinois rivers into parts of southwest Illinois. 

Numerous medium to large tree limbs along with uprooted trees damaged a number of roofs and gutters on homes and vehicles in Jerseyville, Illinois between 6:00 and 6:10 PM CDT.  Several witnesses from Jerseyville indicated that winds of 60 mph and greater occurred for approximately 3 to 5 minutes with the strongest gusts occurring near the early stages of heavy rainfall. Shingles and insulation from two businesses near the south side of town were ripped off while some sheet metal roofing from a nearby third business was ripped and thrown into a parking lot.  A light pole in the parking lot was also snapped.  Much of the damage occurred along the eastern and southern sides of Jerseyville.  Winds were estimated between 65 to 75 mph over this area with the stronger winds in the vicinity of the microbursts.  Other large trees fell and damaged roofs on homes and smaller outbuildings.

The larger swath of damaging winds moved east-southeastward across the southern part of Macoupin county between 6:30 and 6:50 PM CDT.  Several microburst were identified over this area.  Fallen trees damaged a home south of Bunker Hill and another one 4 miles east of Brighton, Illinois.  Several large trees were snapped at the base or uprooted mainly over the western two thirds of southern Macoupin County.  Some corn was also flattened in the areas of the microbursts.  Only minor tree damage was uncovered in the Staunton, Illinois area.  Winds were again estimated between 65 to 75 mph with the stronger speeds in the vicinity of the microburst.  Witnesses across southern Macoupin county reported high winds lasting for a period of 3 to 5 minutes. 

The greatest damaging wind swath extended from Mount Olive through Panama area.  Large trees damaged a few homes in rural areas near and east of Walshville, while corn was partially to totally flattened northeast of Panama over the southeast part of Montgomery county.  Wind speeds were estimated between 60 and 70 mph with the stronger gusts in the vicinity of the microbursts.  Another downburst wind area extended from west to east across Litchfield, Illinois.  Mainly medium (and a few large) tree limbs and some power lines were down from west of town to the east southeast of Litchfield. 

 

Damage Photos from around Jerseyville, Illinois

 

WSR-88D Radar Imagery from KLSX (St. Louis)

  (Far Left)  Reflectivity imagery at 6:12 PM CDT from KLSX .  Large mesoscale convective system (MCS) is approaching the eastern part of Jersey County Illinois.  The gust front represents the initial surge of the storm's outflow. Secondary surges from the storm was responsible for the tree and power line damage in Jerseyville and surrounding area.  Several witnesses stated that the period of damaging winds last between 3 to 5 minutes.  This was the result of secondary surges of downdraft air associated with the heavy precipitation reaching the surface.  Based on the damage surface winds ranged from 65 to 75 mph over the Jerseyville area. (Click on image for a larger image).

 

  (Far Left)  Reflectivity image at 6:42 PM CDT from KLSX.  The radar image shows that the large MCS has reached parts of southwestern and south-central Macoupin county.  The initial storm's outflow (gust front) has accelerated as much as 5 to 7 miles ahead of the stronger precipitation area and is approaching the Staunton, Illinois area.  Note the medium green area ahead of the higher reflective yellow and red area (heavier precipitation) 6 to 8 miles west-northwest of Staunton represents the secondary surge of stronger downdraft air causing damaging winds.  Several large trees were snapped in this area along Staunton-Bunker Hill Road.

 

  (Far Left)  Reflectivity image at 7:11 PM CDT.  The storm complex is starting to transition to a bow echo.  The strongest swath of wind damage occurred along the southern Montgomery - northern Bond county areas.  One swath of stronger wind damage occurred between Mount Olive and Walshville and to the Panama-Donnelson area.  A lesser degree of wind damage occurred across the Litchfield-Hillsboro area.

 


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