Tornadoes · United States · Texas · 2015

EF0 tornado, Knox City, Texas, April 22, 2015

This EF0 tornado ran 0.2 miles across Knox County on April 22, 2015, touching down at 9:50 PM CDT and reaching 30 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
April 22, 2015
Touchdown
9:50 PM CDT (02:50 UTC)
Path length
0.2 miles (0.3 km)
Path width
30 yards (27 m)
Deaths
0
Injuries
0
County
Knox County
Touchdown point
33.481, -99.894
Lift-off point
33.481, -99.894
Record number
1504222050-01

What the Weather Service recorded

A complex of storms raced southward across west Texas ahead of a southward moving cold front. To the east of this area of storms, scattered supercells developed during the evening hours, producing very large hail and at least one tornado near Knox City. Storms gradually moved southward through the evening.

A brief tornado was reported by emergency management about 6 miles northwest of Knox City. No damage is known to have occurred with this tornado.

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

The warnings

17 minutes of warning. NWS OUN issued a tornado warning for this county at 02:33 UTC, 17 minutes before the tornado touched down, in force until 03:15 UTC.

The county was under a tornado watch, issued at 19:56 UTC and running to 05:00 UTC.

Issued (UTC)ExpiredProductOffice
19:56 UTC05:00 UTCTornado WatchOUN
02:11 UTC03:30 UTCSevere Thunderstorm WarningOUN
02:33 UTC03:15 UTCTornado WarningOUN
03:12 UTC04:00 UTCTornado WarningOUN
03:45 UTC06:45 UTCFlood AdvisoryOUN

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 Enhanced Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 00:46 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.

Fort Worth, TX (KFWD), 00:00Z

2.8 hours before the tornado, 253 km from the path. April 23, 2015.

Skew-T log-pSkew-T log-p diagram, Fort Worth, TX at 00:00Z on 2015-04-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 800 joules per kilogram, CIN -5, lifted condensation level 1005 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 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, Fort Worth, TX at 00:00Z on 2015-04-23The 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 91 square meters per square second, 0 to 6 km bulk shear 75 knots.1939587897117136Sfc1 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
800 J/kg
Mixed-layer CIN
-5 J/kg
Surface CAPE
1806 J/kg
Mixed-layer LCL
1005 m above ground
0-6 km bulk shear
75 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
91 m²/s²
0-3 km storm-relative helicity
238 m²/s²
Significant tornado parameter
1.2
Supercell composite
8.3
0-3 km lapse rate
6.5 K/km

Open this sounding in Storm Lab

Fort Worth, TX (KFWD), 12:00Z

9.2 hours after it, 253 km from the path. April 23, 2015.

Skew-T log-pSkew-T log-p diagram, Fort Worth, TX at 12:00Z on 2015-04-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 200 joules per kilogram, CIN -118, lifted condensation level 546 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 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, Fort Worth, TX at 12:00Z on 2015-04-23The 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 179 square meters per square second, 0 to 6 km bulk shear 43 knots.1939587897117Sfc1 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
200 J/kg
Mixed-layer CIN
-118 J/kg
Surface CAPE
943 J/kg
Mixed-layer LCL
546 m above ground
0-6 km bulk shear
43 kt
0-1 km bulk shear
19 kt
0-1 km storm-relative helicity
179 m²/s²
0-3 km storm-relative helicity
195 m²/s²
Significant tornado parameter
0.1
Supercell composite
4.0
0-3 km lapse rate
4.9 K/km

Open this sounding in Storm Lab

The radar

The Dyess AFB radar (KDYX), 121 km away, was scanning. The volume nearest the touchdown began at 02:50 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.

What was reported nearby

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

Time (UTC)ReportWhereCountyRemark
02:33 UTCHAIL 1.759 S PaducahCottle, TXHAIL COVERING THE ROAD.
02:50 UTCTORNADO6 Nw Knox CityKnox, TXA BRIEF ROPE TORNADO REPORTED BY KNOX COUNTY EM
03:19 UTCTORNADO5 N Knox CityKnox, TXBRIEF TOUCHDOWN. RELAYED BY NWS EMPLOYEE
03:20 UTCTSTM WND DMG1 Wsw GuthrieKing, TXROOF BLOWN OFF BARN AT FOUR SIXES RANCH. TIME ESTIMATED.
03:30 UTCHAIL 1.511 Ene WeinertHaskell, TXTHE PUBLIC REPORTED
03:38 UTCHAIL 35 N Knox CityKnox, TX
03:43 UTCHAIL 2Knox CityKnox, TX
03:46 UTCFUNNEL CLOUD2 Nw WeinertHaskell, TX
03:52 UTCFUNNEL CLOUD3 Nw WeinertHaskell, TX
04:01 UTCHAIL 2.75WeinertHaskell, TX

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 TexasEvery tornado in Texas since 1950Warnings in force in Texas nowThe forecast where you are

The other tornadoes of April 22, 2015

3 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 226:18 PM CDTEF0Scurry, TX0.050
April 226:20 PM CDTEF0Nolan, TX0.130
April 227:53 PM CDTEF0Floyd, TX0.150

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.