Thunderstorm Wind — Nelson, Kentucky

2023-07-02 · near Chaplin, Nelson, Kentucky

Event narrative

There were trees and power lines down.

Wider weather episode

An anomalously strong mid- and upper-level trough for early July was centered over the Plains and gradually moved eastward toward the Ohio Valley on July 1st and 2nd, 2023. A meandering surface frontal boundary gradually became more well defined throughout this period, with a warm front lifting through the Ohio Valley on July 1st before a series of remnant outflow boundaries and a convectively-enhanced cold frontal passage occurred July 2nd into the morning hours of July 3rd. Across central Kentucky and southern Indiana, there was ample fuel for convection, as temperatures in the mid-to-upper 80s and lower 90s and dewpoints in the low-to-mid 60s allowed for the development of over 2500 J/kg of mixed-layer CAPE. Since there was initially no predominant organizing feature for convection, multiple waves of showers and thunderstorms moved across the region on July 1st, producing intermittent instances of damaging straight-line winds and near-severe hail, primarily across southern Indiana. However, as the main trough and the surface cold front moved into the region on July 2nd, convection was better organized thanks to 40-45 knots of effective bulk shear in addition to moderate to high levels of instability. Convective development on July 2nd began during the early afternoon hours across southwestern Indiana and western Kentucky. Initially, convective mode was predominantly cellular, but cells gradually grew upscale through the afternoon into clusters and larger quasi-linear structures. Downdraft CAPE was over 1000 J/kg and significant hail parameter values exceeded 1 through most of the area; accordingly, strong to damaging winds and hail were the primary severe hazards observed during the afternoon and evening hours on July 2nd. However, there was just enough low-level helicity to facilitate the development of two weak tornadoes, one in Anderson County and the other in Casey County. Storms gradually subsided after sunset, with the severe threat ending across the region by midnight on July 3rd.

View location on OpenStreetMap → (37.9000, -85.2200)

Source: NOAA Storm Events Database, event_id 1128017. Narrative written by the NWS forecast office that issued the report.