October 24, 2001 Squall Line Event

During the evening of October 24, 2001, an extensive severe squall line raced across the Ohio Valley, producing widespread straight-line winds of 50-60 mph with some gusts from 60-80 mph across central Kentucky and south-central Indiana. This resulted in many downed trees and power lines, and minor structural damage. Damage was most significant along bowing line segments (bow echoes) embedded within the line. There also were a few supercell thunderstorms that developed just ahead of the line that produced large hail. These storms merged quickly with the rapidly moving squall line. Supercells were more common across central and northern Indiana, some of which produced damaging tornadoes in northern Indiana. The images below show reflectivity data from parts of the squall line as viewed from our KLVX WSR-88D. In addition, a reflectivity loop of the 8 labeled images below also is available. At bottom are two pictures showing some of the damage that occurred in Jefferson County, Kentucky near Louisville.

The above WSR-88D 0.5 degree reflectivity images show the progression of the squall line across north-central Kentucky and south-central Indiana. The line moved east at 50-60 mph. Severe storms were present along the leading edge of the line, where a tight reflectivity gradient suggested strong convergence, intense updrafts, and a potent gust front that produced wind damage. Behind the leading line was lighter rainfall (green and yellow colors). The images indicate that very strong storms moved across Harrison County, Indiana, which then bowed out as they plowed across Jefferson and Shelby Counties in Kentucky. South of this bow, another bowing line segment moved across southern Breckinridge, Hardin, and into Nelson Counties. Large hail also was reported in Hardin County. A loop of the images in shown at left.
The reflectivity image above shows a portion of the squall line in south-central Kentucky. At this time, a supercell thunderstorm was embedded in the line across west-central Barren County east of Bowling Green. Note the dark red and pink colors in the southwest part of the storm along the Allen/Warren/Barren County border. This represents large hail and very heavy rain within the storm. The image above shows the squall line as it raced across Perry County, Indiana. Note the intense storms within the bowing line segment in western Perry County. The highest reflectivity values (red colors) showed a line echo wave pattern (LEWP) within the bow, indicative of enhanced surface wind damage. Such signatures also can be associated with transient tornadoes.
The image above taken in western Jefferson County, Kentucky shows some of the aftermath of the squall line. A large tree was uprooted which fell on a house due to the force of straight-line winds associated with a bow echo within the squall line.
As the bow echo raced across southern Jefferson County, Kentucky, severe straight-line winds caused a power pole to snap (far background). The weight of the fallen snapped pole caused additional poles (foreground) to become bent as well.

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