EF0 tornado, Aurora to Watkins, Colorado, May 21, 2014

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 21, 2014

Touchdown

2:30 PM MDT (20:30 UTC)

Path length

0.1 miles (0.2 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Adams County

Touchdown point

39.761, -104.810

Lift-off point

39.761, -104.810

Record number

1405211430-01

Severe thunderstorms occurred in and around the Denver area. The storms produced large hail, from quarter to golfball size. Frontier Airlines canceled 16 flights, when several planes sustained hail damage. Forty flights at Denver International Airport were either delayed or canceled. Some homes in Green Valley Ranch east of Denver were damaged by hail. Several vehicles were also damaged. Five short lived tornadoes touched down but no damage was reported. ||The storms also produced heavy rain and strong damaging winds. The wind downed trees and power lines east of Denver. The heavy rain and hail, up to 6 inches deep in spots, caused street flooding around the metro area. The hailstorm at Dick���s Sporting Goods Park knocked out power to the stadium where the 4A and 5A girls soccer championship games were about to be played. The inclement weather snarled traffic on Interstate 70, Pe��a Boulevard, U.S. 85 and elsewhere due to the flooded roads. In some areas, snow plows were called out to clear the hail. Parts of Tower Road and Peoria Street, and other roads in Commerce City, were closed through the late evening hours, because of standing water. Several vehicles stalled in standing water where water pooled in the underpasses.

A tornado touched down briefly. No damage was observed.

A tornado touched down briefly. No damage was observed.

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

34 minutes of warning. NWS BOU issued a tornado warning for this county at 19:56 UTC, 34 minutes before the tornado touched down, in force until 20:30 UTC.

The county was under a tornado watch, issued at 18:34 UTC and running to 00:42 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 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:56 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 Denver radar (KFTG), 23 km away, was scanning. The volume nearest the touchdown began at 20:27 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 2014 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

9 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.