Episode narrative: A strong storm system moved through the eastern half of the United States from December 9th-11th, 2023. The storm system was supported by a broad upper level trough which deepened and amplified over the central and eastern CONUS on December 9th. At the surface, a cold front over the Mississippi Valley on the morning of the 9th gradually moved eastward across Kentucky and Tennessee through the afternoon and evening hours. Ahead of the cold front, low level warm and humid air from the Gulf of Mexico was lifted northward into Middle Tennessee and South Central Kentucky, which when combined with approaching cold air in the mid-levels of the atmosphere, provided enough instability to develop showers and thunderstorms in the pre-frontal environment during the afternoon and evening hours on December 9th.

Although instability was an important ingredient for the development of thunderstorms, the amount of vertical wind shear in the atmosphere was the key factor that gave storms the potential to become strong and severe. While winds near the ground ranged from 10 to 15 mph out of the south and southeast, winds 4000-5000 feet off the ground were 45 to 55 mph out of the southwest. This combination of changing wind direction and increasing wind speed allowed for the development of supercell thunderstorms, which began to form across west and northwest Tennessee just after noon. Storms continued to increase in intensity during the early afternoon hours, with one particular supercell west of Clarksville, Tennessee becoming the primary storm of concern for our area. A tornado formed near the perimeter of Fort Campbell before moving northeast, producing up to EF-3 damage in northern Montgomery County, TN. The cell then crossed into Kentucky in southern Todd County, where it was on the ground for over 13 miles, producing up to EF-2 damage.

The tornado continued into the NWS Louisville County Warning Area near the community of Allensville on the Todd/Logan County line. In Logan County, the tornado remained on the ground for over 22 miles, producing up to EF-2 damage with maximum estimated winds of 115 mph. The tornado barely crossed into far northwestern Simpson County before lifting about 2 miles southeast of Auburn. However, rotation just off the ground within the mesocyclone remained strong, with funnel clouds being observed as the storm passed through extreme northwestern Simpson County and into southwestern Warren County. Ultimately, a second tornado from the same storm touched down on the south side of Bowling Green, producing up to EF-1 damage with maximum estimated winds of 90 mph over a path of around two and a quarter miles.

Later in the evening, a third tornado also touched down in far northern Clay county Tennessee and then moved across the state line into Monroe county Kentucky. This brief EF-1 tornado did most of its damage near the Harlan Crossroads community before lifting.

Tornado event in MONROE County, KENTUCKY
Start: 09-DEC-23 18:07:00
End: 09-DEC-23 18:11:00
Direct deaths: 0
Event narrative: A brief  EF-1 tornado touched down just south of the Kentucky border in Clay County where it blew down a few trees on Barber Shop Road (EF-0). The tornado intensified to EF-1 as it moved northeast into Kentucky and caused significant roof and siding damage to several chicken barns in Harlan Crossroads. A home also lost its porch and part of its roof on Red Hill-Beech Grove Road. A few more trees were blown down west of of Beech Grove-Boles Road before the tornado lifted.