Thunderstorm Wind — Simpson, Kentucky

2025-05-16 · near Franklin, Simpson, Kentucky

Event narrative

A large tree limb was blown down behind a home in Franklin.

Wider weather episode

A strong storm system moved across the central and eastern United States from May 16th into May 17th, producing a significant severe weather event across the Mississippi and Ohio Valley. An unusually deep closed upper low slowly moved across the upper Midwest on the 16th, with strong mid- and upper-level southwest flow overspreading the Mississippi and Ohio Valley. The upper low pressure system brought a surface cold front into the Mississippi Valley by the morning of May 16th, with the front stalling out over the region until clearing to the east by the morning hours of May 17th. Ahead of the cold front, a typically unstable late spring air mass was present, with temperatures in the 80s and dewpoint temperatures in the upper 60s and lower 70s. The combination of strong wind shear for mid-May and a moist, unstable environment set the stage for severe weather across central Kentucky and southern Indiana.

During the early morning hours on May 16th, discrete cells, some supercellular, began to develop along the Ohio River and across central Kentucky. These cells were assisted by a 35 knot southwesterly low-level jet, which provided enough instability via low-level moisture transport for convection to initiate. Most of the morning convection was elevated, with between 2000-3000 J/kg of most unstable parcel CAPE present above a relatively stable boundary layer. Given the strong flow aloft, effective bulk shear was strong, around 55-60 kt, supporting organized multicell and supercell clusters. For the first wave of storms which moved across central Kentucky during the morning hours, large hail was the primary severe threat, with several reports of quarter to ping pong ball sized hail reported in severe storms. By later in the morning, isolated wind damage was also observed with severe storms across south central Kentucky. The first wave of storms continued until around midday, with a lull in activity occurring through the late afternoon hours.

During the early and mid-afternoon hours, breaks in cloud cover allowed for additional destabilization to occur, with temperatures warming into the low 80s and dewpoint temperatures in the low 70s ahead of the second wave of severe storms. This would support between 3500-4500 J/kg of surface-based CAPE across central Kentucky and extending into southern Indiana, setting up quite an unstable environment. Wind shear values were also extremely high ahead of the second wave of storms, with 60-70 knots of effective bulk shear noted in mesoanalysis data. Strong low-level wind shear and helicity were also present, with the parameter space supporting significant threats from damaging winds, hail, and tornadoes. The second wave of storms began as a broken line of supercells across Missouri, which moved into western and central Kentucky during the early evening hours. A dominant lead supercell moved across south central Kentucky, producing significant wind damage and up to baseball sized hail as it tracked from Logan and Butler County across to Russell County. As the supercell moved across Russell County, rotation aloft within the cell translated to the ground, with the storm producing a strong tornado which produced up to EF3 damage in eastern Russell County before tracking for nearly 60 miles across southeastern Kentucky, with maximum damage of EF4 strength near London. Additional supercells farther to the north also produced isolated wind damage and hail. By the late evening hours, supercells across western Kentucky and southern Illinois merged into a squall line as it moved over central Kentucky, producing larger swaths of wind damage with several reports of over 60 mph winds. A spin-up tornado was also observed with this line over Logan County, producing EF1 damage. The line of severe storms finally pushed into eastern Kentucky during the early morning hours on May 17th, bringing an end to the severe weather threat.

View location on OpenStreetMap → (36.7200, -86.5800)

Source: NOAA Storm Events Database, event_id 1267378. Narrative written by the NWS forecast office that issued the report.