Thunderstorm Wind — Harrison, Indiana

2023-06-25 · near Breckenridge, Harrison, Indiana

Event narrative

The National Weather Service conducted a storm assessment survey with Harrison County Emergency Management and private meteorologist August Veron for the storms on Sunday evening June 25. There was sporadic wind damage in the Lanesville community, with the most concentrated area along SR 62 near the Floyd county line. Trees were topped and snapped, and there were power lines down and 3 power poles snapped. Winds were estimated to be between 70 and 75 mph. All of the damage was facing from the west northwest to the east southeast. There was no indication of tornadic rotation.

Wider weather episode

An anomalously strong mid- and upper-level trough for late June moved across the Great Lakes and Ohio Valley on June 25th. A 60-70 kt 500 mb jet bisected the mid-Mississippi Valley, placing central Kentucky and southern Indiana in the left exit region, contributing to broad rising motion over the area. Near the surface, a well-defined cold front crossed the Mississippi River during the mid-to-late afternoon hours on June 25th, with temperatures in the upper 80s and lower 90s and dewpoints in the upper 60s and lower 70s in the warm sector ahead of the front. In the warm sector, mixed-layer CAPE of 2500-3500 J/kg provided plenty of fuel for convective development aside from the aforementioned favorable jet forcing. With 25-35 knots of flow at 850 mb, there was also ample vertical wind shear across the region, with effective bulk shear values generally above 45 kt, leading to the development of supercellular structures. The parameter space was favorable for all severe hazards. 0-1 km storm-relative helicity was over 200 m2/s2 and significant tornado parameter values were frequently greater than 1, suggesting the potential for rotating mesocyclones and tornadoes. Downdraft CAPE was over 1200 J/kg along and west of Interstate 65, suggesting the potential for strong winds from any formidable downdrafts. Finally, sufficient mid-level lapse rates and significant hail parameter values warranted concerns for severe hail. As would be expected given the parameter space, all severe hazards were observed, with a couple tornadoes and numerous straight-line wind and hail reports across southern Indiana and central Kentucky. Straight-line winds of up to 100 mph and multiple reports of golf ball or larger size hail serve as evidence of the highly unusual setup across the Ohio and Tennessee valleys June 25th.

View location on OpenStreetMap → (38.2220, -86.0140)

Source: NOAA Storm Events Database, event_id 1119183. Narrative written by the NWS forecast office that issued the report.