EF1 tornado, Cortland to Holland, Nebraska, May 6, 2015

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 6, 2015

Touchdown

10:49 PM CDT (03:49 UTC)

Lifted

10:59 PM CDT (03:59 UTC)

On the ground

10 minutes

Path length

7.7 miles (12.3 km)

Path width

500 yards (457 m)

Deaths

0

Injuries

0

Counties

Gage and Lancaster counties

Touchdown point

40.506, -96.709

Lift-off point

40.593, -96.619

Record number

1505062149-01

40 damage points were recorded along this path by NWS OAX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 98 mph.

• trees uprooted 1//4 mile east
• small tower (50ft) collapsed at water treatment plant.
• part of roof off. shed torn apart
• Metal Pole Bent at base. This southern one may have gone over due to stress on lines.

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

A storm system moving through the central plains allowed for low pressure to develop over the high Plains, and a warm front to lift north into the northern Plains. Thunderstorms developed during the early afternoon along a sharping dry line over central Plains and moved northeast. Moisture and thunderstorms moved into eastern Nebraska and southwest Iowa during the late afternoon hours. As shear increased during the evening isolated severe weather was observed over southeast Nebraska, mainly in the form of strong winds and 1 EF1 tornado. Although isolated severe weather occurred, training thunderstorms resulting in extremely heavy rainfall and flash flooding across many areas of southeast Nebraska.

A damage survey indicated a weak tornado developed near Cortland and traveled to the northeast. Damage in Cortland and surrounding areas of Gage County consisted of large tree branches and some minor shed damage. This tornado then continued into Lancaster County.

This tornado continued from Gage County into Lancaster County. The damage along the path of the tornado was generally minor and consisted of outbuildings, large tree branches, and downed power lines. The tornado appeared to reach its maximum intensity along Princeton Road and between 38th and 54th streets. Here several farmsteads were impacted where roof damage to homes was noted, and high-tension power lines were downed.

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

11 minutes of warning. NWS OAX issued a tornado warning for this county at 03:38 UTC, 11 minutes before the tornado touched down, in force until 04:02 UTC.

The county was under a tornado watch, issued at 01:31 UTC and running to 07:00 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 01:01 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.

The Omaha radar (KOAX), 89 km away, was scanning. The volume nearest the touchdown began at 03:49 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 2015 tornado in NebraskaEvery tornado in Nebraska since 1950Warnings in force in Nebraska nowThe forecast where you are

47 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.