EF1 tornado, Ong, Nebraska, May 17, 2017

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mph

   Considerable damage. Roofs torn off well-built houses, frame homes shifted on their foundations, mobile homes destroyed, large trees snapped or uprooted, cars lifted off the ground.

4. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. EF5over 200 mph

   Incredible damage. Strong frame houses swept off their foundations, car-sized missiles thrown more than 100 meters, steel-reinforced concrete badly damaged, high-rise buildings deformed.

7. Unrated

   The survey recorded a tornado but could not put a number on it, most often because it crossed open country and damaged nothing a rating can be read from.

Rating

EF1

Date

May 17, 2017

Touchdown

1:24 AM CDT (06:24 UTC)

Lifted

1:29 AM CDT (06:29 UTC)

On the ground

5 minutes

Path length

2.2 miles (3.5 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Clay County

Touchdown point

40.452, -97.939

Lift-off point

40.459, -97.898

Record number

1705170024-01

2 damage points were recorded along this path by NWS GID, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 90 mph.

• 4-5 large trees uprooted. Trunk snapped on one dead tree. Several outbuildings w/minor damage. Tin lofted 20 feet into tree. Small branches lofted into power lines.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Thunderstorms produced damaging winds and some low-end severe hail over several counties in south central Nebraska on this Tuesday evening and night. Scattered single cell thunderstorms began developing around 3 PM CST from central Kansas northeast into southern Nebraska. The formation of numerous cells quickly resulted in a transition to a multicell convective mode by 4 PM CST. This nearly continuous line of storms lifted north, crossing much of south central Nebraska between 5 and 8 PM CST. As this occurred, another cluster of multicells over north central Kansas merged and moved northeast, eventually taking on the shape of a bow echo. This line of storms affected areas from Nelson and Hebron up to York between 630 and 730 PM CST. More storms over southwest Nebraska and northwest Kansas eventually consolidated and crossed south central Nebraska as a small scale bow echo between 10 PM and 130 AM CST. The initial line lifting north produced a fairly large area of severe winds from the state line north to Holdrege and Grand Island. A grain bin was removed from its foundation and deposited on Highway 74 near the town of Roseland, in Adams County. A tractor-trailer was blown over on Interstate 80 as well, just south of Grand Island. The highest gust measured was 67 mph at the Holdrege airport. A brief EF-0 landspout tornado was photographed near the town of Exeter. The eastern portion of this line produced the most hail, with a few reports of 1 inch hail over Fillmore, Nuckolls, and Thayer Counties. The bow echo taking shape from Nelson to York snapped a few power poles in eastern Thayer County. The last line of storms to cross the area produced mostly sub-severe winds of 50 to 55 mph. However, severe winds did occur in a couple locations. The highest measured gust was 64 mph in the town of Norman, in eastern Kearney County. A brief EF-1 tornado also occurred in Clay County, just north of the town of Edgar. It was on the ground for approximately 2 miles, damaging outbuildings, trees, and overturning irrigation pivots. This tornado occurred just after midnight CST. Repeated thunderstorm activity resulted in 1 to 2 inches of rain over much of south central Nebraska. There were even a couple reports in excess of 3 inches. Ditches were full of water, and even some minor flooding of low-lying areas occurred near Highway 136 just west of the town of Inavale, and also near the intersections of Highways 81 and 92 west of Osceola.||Low pressure was over South Dakota, and its trailing weak cold front moved into south central Nebraska during the day. It became stationary as low pressure formed over southeast Colorado and deepened to near 990 mb. In the upper-levels, a longwave trough was over the Western U.S. with a ridge over the East. A strong shortwave trough lifted out of the Desert Southwest into the Southern Plains, while a closed low dropped into the Pacific Northwest. In the preconvective environment, an elevated mixed layer had overspread a moist boundary layer. Mid-level lapse rates were between 8 and 9 C/km. MUCAPE was between 3000 and 4500 J/kg. With strong dynamic forcing, deep layer shear was very strong, between 40 and 60 kt.

A brief EF-1 tornado touched down northeast of Edgar. The tornado remained on the ground for approximately 2 miles, resulting in damage to 2 farmsteads. The damage was confined mainly to outbuildings and trees. A few center irrigation pivots were also damaged along its path. The maximum wind speed was estimated to be 90 MPH.

From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

Every warning and watch covering the touchdown point that day, from the Iowa Environmental Mesonet's archive of National Weather Service products. Lead time is measured from the issue of the warning in force to the touchdown time in the database, both of which were recorded to the minute by different people.

The Storm Prediction Center had this point in a Marginal Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 05:40 UTC.

SPC's Day 1 convective outlook as it stood when the tornado began, read at the touchdown point. The same archive is on the radar archive.

The radiosonde launches on either side of the tornado, from the nearest station that was launching then, drawn and analyzed the way Storm Lab does: the same diagram, the same parcel and shear definitions SPC's mesoanalysis uses.

Hebron (HJH), 44 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The Grand Island radar (KUEX), 47 km away, was scanning. The volume nearest the touchdown began at 06:25 UTC.

Open the radar archive at this moment, over the track

Reflectivity and velocity, decoded from the Level II archive in the browser. Volumes take a few seconds to open the first time.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2017 tornado in NebraskaEvery tornado in Nebraska since 1950Warnings in force in Nebraska nowThe forecast where you are

15 more were confirmed in the United States that day.

Ratings are the survey's, read off the damage rather than measured; the rating scale is above. Tornado counts rise through the record as reporting improved, so a year in the 1950s is not comparable with one today except for the strongest tornadoes, which were always noticed.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.