Tornadoes · United States · Colorado · 2015

EF0 tornado, Leader to Strasburg, Colorado, May 15, 2015

From Leader to Strasburg, this EF0 tornado ran 0.1 miles across Adams County on May 15, 2015, touching down at 2:03 PM MDT and reaching 50 yards wide. It killed nobody.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  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.

The record

Rating
EF0
Date
May 15, 2015
Touchdown
2:03 PM MDT (20:03 UTC)
Path length
0.1 miles (0.2 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Adams County
Touchdown point
40.000, -104.140
Lift-off point
40.000, -104.140
Record number
1505151403-01

What the Weather Service recorded

Severe thunderstorms produced hail, from nickel to half dollar size, across parts of Adams, Arapahoe, Douglas and Weld Counties. Two tornadoes touched down briefly in Adams County; one destroyed a storage shed. Later in the evening, a severe thunderstorm produced large hail, up to ping pong size, in Phillips and Sedgwick Counties.

A tornado briefly touched down in open country. No damage was observed.

A tornado touched down briefly and extensively damaged a storage shed.

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

The warnings

5 minutes of warning. NWS BOU issued a tornado warning for this county at 19:58 UTC, 5 minutes before the tornado touched down, in force until 20:23 UTC.

Issued (UTC)ExpiredProductOffice
18:49 UTC19:30 UTCSevere Thunderstorm WarningBOU
19:21 UTC19:48 UTCSevere Thunderstorm WarningBOU
19:35 UTC20:00 UTCTornado WarningBOU
19:58 UTC20:23 UTCTornado WarningBOU

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 forecast that day

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 19:54 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 air that afternoon

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.

Denver, CO (KDEN), 12:00Z

8.1 hours before the tornado, 79 km from the path. May 15, 2015.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2015-05-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 15 joules per kilogram, CIN -265, lifted condensation level 1417 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Denver, CO at 12:00Z on 2015-05-15The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -28 square meters per square second, 0 to 6 km bulk shear 24 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
15 J/kg
Mixed-layer CIN
-265 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1417 m above ground
0-6 km bulk shear
24 kt
0-1 km bulk shear
10 kt
0-1 km storm-relative helicity
-28 m²/s²
0-3 km storm-relative helicity
-6 m²/s²
Significant tornado parameter
0.0
Supercell composite
-0.0
0-3 km lapse rate
4.8 K/km

Open this sounding in Storm Lab

Denver, CO (KDEN), 00:00Z

3.9 hours after it, 79 km from the path. May 16, 2015.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2015-05-16Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 411 joules per kilogram, CIN -19, lifted condensation level 1427 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Denver, CO at 00:00Z on 2015-05-16The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -10 square meters per square second, 0 to 6 km bulk shear 60 knots.1939587897Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
411 J/kg
Mixed-layer CIN
-19 J/kg
Surface CAPE
1207 J/kg
Mixed-layer LCL
1427 m above ground
0-6 km bulk shear
60 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
-10 m²/s²
0-3 km storm-relative helicity
73 m²/s²
Significant tornado parameter
-0.0
Supercell composite
-0.3
0-3 km lapse rate
8.3 K/km

Open this sounding in Storm Lab

The surface observations

Front Range (FTG), 42 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
18:50 UTC62.650350° 7 kt1005.8VCTS
19:53 UTC60.857.2300° 9 kt1005.4
20:47 UTC64.450330° 9 kt1005.1
21:50 UTC60.853.6270° 11 kt1005.8-RA

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

What was reported nearby

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

Time (UTC)ReportWhereCountyRemark
20:03 UTCTORNADO4 Wsw HoytAdams, CO

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

This ground now

The live radar over the trackEvery 2015 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

The other tornadoes of May 15, 2015

11 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 156:29 AM CDTEF1La Salle, TX2.3501$100,000
May 156:44 AM CDTEF0La Salle, TX0.830$50,000
May 1511:18 AM CDTEF0Duval, TX0.010
May 151:05 PM CDTEF0Nueces, TX0.225$25,000
May 151:20 PM CDTEF0San Patricio, TX1.4503$100,000
May 152:51 PM MDTEF1Adams, CO0.1100$15,000
May 153:34 PM MDTEF1Goshen, WY9.8400
May 156:22 PM CDTEF0Jackson, KS0.120
May 157:41 PM CDTEF0Brown, KS0.120
May 157:34 PM MDTEF0Cherry, NE0.120
May 158:08 PM MDTEF0Sheridan, NE0.010

What this means

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.

Sources

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