Thunderstorm Wind — Kearney, Nebraska

2014-06-14 · near Wilcox, Kearney, Nebraska

Event narrative

Wind gusts estimated to reach near 80 MPH at times moved through the county, resulting in numerous overturned irrigation pivots and downed trees.

Wider weather episode

During a month that had several rounds of severe weather in South Central Nebraska, what transpired on this Saturday evening into the very early morning of Sunday the 15th was likely one of the most significant severe weather events of the entire 2014 convective season, especially in terms of widespread wind damage that raked from west-to-east through most locations near and south of Interstate 80 during the later evening. Earlier in the event, more discrete convection resulted primarily in numerous reports of severe-criteria hail, some as large as tennis ball to grapefruit size, along with four confirmed, brief EF0 tornadoes that yielded no reports of damage. The first of these tornadoes occurred in northwestern Franklin County near Hildreth around 730 pm CDT. The other three tornadoes were associated with a supercell storm that drifted northeast out of Kansas along a path from Webster to Hamilton counties before being absorbed into a larger line of convection. The first of these tornadoes was sighted in far southwestern Webster County around 830 pm CDT while the final two brief touchdowns occurred after nightfall in southwestern Hamilton County between Trumbull and Giltner between 1000-1030 pm CDT. In terms of hail, the largest confirmed stone of 4.25 fell three miles southeast of Hastings around 930 pm CDT. Other notable hail reports included stones up to baseball size along the Nance-Merrick County line, in and near Gibbon, near Ayr and in Arapahoe. However, in terms of widespread damage, the aforementioned severe squall line that rolled across roughly the southern half of the 24-county area later in the evening ended up being the big story of this event. Based on known wind and damage reports (which likely only represented a fraction of the total, individual instances of storm damage across the area), this north-to-south oriented squall line produced a swath of 60-90 MPH gusts through essentially all areas between Interstate 80 and the Kansas border. In addition to several estimated severe wind speeds, a few of the most intense measured gusts included 82 MPH by a storm chaser near the Interstate 80 York exit, 79 MPH at Hastings airport, and 76 MPH at home weather stations near Davenport and Ohiowa. Needless to say, a significant amount of wind damage occurred with this squall line as it uprooted or mangled countless trees and also damaged several structures, including outbuildings, grain bins and power poles. To cite just a few examples of this damage as it progressed from west to east: at Harlan County Lake at least four small boats were rammed into the shore and a camping trailer was overturned onto a vehicle, in Guide Rock a garage was blown off its foundation and partially onto a roadway, and at the Nuckolls County fairgrounds in Nelson a tin roof was removed from a barn, the roof of the arena was damaged and a camper was flipped on its side. Due to the fairly progressive nature of most storms, rainfall totals across much of South Central Nebraska did not exceed 1-2 inches. However, a southwest-to-northeast corridor of 2-3 and locally higher rainfall centered roughly 15 miles either side of a line from Wilcox-Grand Island-Genoa, featuring NeRAIN observer totals of 4.13 three miles west-southwest of Genoa and 4.06 two miles of Doniphan.

Breaking down event timing, the initial round of at least semi-discrete convection, including a few supercells, flared up between 530-730 pm CDT within a fairly narrow southwest-to-northeast oriented corridor along a slow-moving but well-defined cold front. Most of this early convection concentrated several miles either side of a line from near Franklin and Red Cloud in the south, then north-northeast through the Hastings-Grand Island-Central City-Fullerton areas. Generally between 730-930 pm CDT, this initially narrow corridor of storms gradually expanded in coverage to both the west and east. Then, even as ongoing convection remained strong to severe, the leading edges of the incoming, intense squall line raced out of southwest Nebraska, entering southwestern portions of the local area between 930-1030 pm CDT. For the next few hours generally between 1030 pm to 1 am CDT, this fierce, bowing line raced across the remainder of roughly the southern half of South Central Nebraska, while the far northern end of the line gradually merged with the earlier convection that had largely lifted north of Interstate 80 by this time and had weakened somewhat. Finally, between 1-2 am CDT, the line of severe storms cleared the far eastern edges of the local area near the Highway 81 corridor, leaving behind only a trailing zone of stratiform rain that lingered into the pre-dawn hours.

On the synoptic scale, this was a fairly classic June setup for significant severe, as a progressive mid level shortwave trough kicked out of the Rockies and into the Central Plains, rotating around the southeast periphery of a parent closed low anchored over the Montana/Saskatchewan border area. As this occurred, strengthening and increasingly-diffluent mid-upper southwesterly flow overspread the local area. At the surface, a slow-moving cold front edged eastward into South Central Nebraska during the day, embedded within an elongated 992-996 millibar low pressure center stretched from western Kansas into eastern Nebraska by early evening. During the late-afternoon to mid-evening time frame, temperatures gradually decreased from highs in the upper-80s to lower-90s F while dewpoints generally held in the mid-60s F. Mesoscale severe weather parameters during the early-mid evening featured 2000-3000 J/kg mixed layer CAPE in the presence of 40-60 knots of 0-6 kilometer deep layer vertical wind shear. As the evening wore on, low level shear intensified as the nose of a 50-60 knot low level jet focused into the area. This severe weather outbreak was well-anticipated a few days in advance at both the local WFO level as well as by the Storm Prediction Center, which already placed most of South Central Nebraska in a Moderate Risk on the Day 2 outlooks 24-48 hours in advance and maintained/expanded the Moderate Risk area into the Day 1 period.

View location on OpenStreetMap → (40.3788, -99.1757)

Source: NOAA Storm Events Database, event_id 524757. Narrative written by the NWS forecast office that issued the report.