EF0 tornado, Giltner, Nebraska, May 12, 2011

1. EF065 to 85 mphthis tornado

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

2. EF186 to 110 mph

   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

EF0

Date

May 12, 2011

Touchdown

4:46 PM CDT (21:46 UTC)

Lifted

4:50 PM CDT (21:50 UTC)

On the ground

4 minutes

Path length

0.8 miles (1.3 km)

Path width

75 yards (69 m)

Deaths

0

Injuries

0

County

Hamilton County

Touchdown point

40.788, -98.061

Lift-off point

40.799, -98.066

Record number

1105121546-01

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 EF0. The highest wind the damage implies is 70 mph.

• Point 2. Estimated lift spot for tornado based upon reports and video.
• Point 1. Estimated location of tornado start.

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

For the second day in a row, severe thunderstorms pounded mainly eastern portions of South Central Nebraska, including many of the same areas affected on the 11th. The majority of severe weather focused near to 30 miles north of the Interstate 80 corridor in Hall, Merrick, Hamilton, Polk and York Counties. Brief, short-track tornadoes also occurred for the second day in a row, with three confirmed EF0 tornadoes. This included one tornado between Aurora and Giltner, and two others a few miles west of Stromsburg. No damage was reported from these brief touchdowns. In addition, the afternoon and early evening featured numerous reports of large hail, along with torrential rainfall and localized flooding. The largest reported hail of 3 inches in diameter occurred just south of Exeter in Fillmore County. Even several hours after severe storms ended across the area, strong northwest winds developed behind the cold front in the evening as the pressure gradient increased, including a measured 58 MPH gust at the York airport. ||This Thursday featured a fairly classic spring setup for severe weather, with a nearly vertically-stacked low pressure system slowly lumbering east near the Nebraska and Kansas border both at the surface and aloft. A nearly stationary surface front arced northeast and east from the low roughly along the Interstate 80 corridor. Meanwhile, a modest dryline swept into the area from the southwest, and a cold front gradually worked southward in the wake of the slow-moving surface low. The combination of these multiple boundaries, along with considerable early afternoon sunshine and the close proximity of the mid-level low pressure system, effectively made this a cold core severe weather situation. While the first strong storm of the day fired up by mid-afternoon in Furnas County nearly directly underneath the mid-level low, the focus quickly turned northeast of the low, with the first severe storms developing in Sherman County around 330 PM. Over the course of the next several hours, severe storms then developed eastward down the Interstate 80 corridor, and southward along the Highway 81 corridor into Fillmore County before gradually slipping eastward out of the area. By late afternoon, the mesoscale environment in the vicinity of the brief tornadoes in Polk County featured 1500 J/kg mixed-layer CAPE, and around 20 knots of low level 0-1km bulk shear. ||Heavy rainfall and flooding were also an issue, especially across a narrow corridor north of Interstate 80. As the severe storms trained over this area, 24-hour rainfall totals of 1.5 to over 4 inches were reported across parts of southern Sherman, southern Howard, far northern Hall, Merrick, northern Hamilton, southwest Polk and northwest York Counties. Some of these areas had just received 1-2 inches of rain in severe storms the day before, thus pushing 48-hour rainfall totals into the 4-6 inch range. The town of Polk reported one of the highest 24-hour and 48-hour rainfall amounts, at 4.34 and 6.12 inches, respectively. This resulted in extensive lowland flooding of fields and small creeks, with water also covering numerous roadways. Even a few days after the rainfall, flooding continued along the Big Blue River in Polk County.

No damage was caused by this brief tornado touchdown.

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. One was issued for the county at another hour that day.

The county was under a tornado watch, issued at 19:38 UTC and running to 03:00 UTC.

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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 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.

Aurora (AUH), 13 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), 62 km away, was scanning. The volume nearest the touchdown began at 21:46 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 2011 tornado in NebraskaEvery tornado in Nebraska since 1950Warnings in force in Nebraska nowThe forecast where you are

2 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.