Link to NWS Louisville Science and Technology Homepage WSR-88D Images: October 24, 2001 Squall Line Event
Green Line Separater

During the evening of October 24, 2001, an extensive severe squall line raced across the Ohio Valley ahead of a powerful cold front and weather system. The line developed across Missouri and Illinois, then moved rapidly east across Kentucky and Indiana and into the Appalachian Mountains overnight. The squall line produced widespread straight-line winds of 50 to 60 mph with some gusts between 60 and 80 mph across central Kentucky and south-central Indiana. This resulted in many downed trees and power lines, and some structural damage, although major structural damage was not reported. 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 then merged quickly with the rapidly moving squall line. These mergers essentially prevented the supercells from remaining isolated ahead of the line long enough to produce tornadoes. However, supercells were even 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 the Ft. Knox-NWS Louisville (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 series of WSR-88D 0.5 degree (low-level) reflectivity images show the progression of the squall line across north-central Kentucky and south-central Indiana. The images are at 10 minute intervals (a finer temporal interval is available). The line moved east at a speed of 50 to 60 mph. Severe thunderstorms 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 widespread wind damage. Behind the leading line was lighter trailing 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 County, Kentucky into Shelby County. South of this bow, another bowing line segment moved across southern Breckinridge County, then through Hardin and into Nelson County.  Large hail also was reported in Hardin County.  A reflectivity loop of these 8 images is available in order to view the movement of the line.  
The 0.5 degree reflectivity image above from Louisville 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 supercell along the Allen/Warren/Barren County border (center of image).  This represents large hail and very heavy rain within the storm. Before the line reached Louisville, it raced through southwest and south-central Indiana. The image above shows low-level reflectivity data as the line plowed 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 that struck the county on the evening of October 24. 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 of image). The weight of the snapped pole that fell caused additional poles (foreground of image) to become bent as well.   

Green Line Separater

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