Tornadoes · United States · Oklahoma · 2021

EF0 tornado, Hollister, Oklahoma, April 27, 2021

This EF0 tornado ran 0.1 miles across Tillman County on April 27, 2021, touching down at 7:15 PM CDT and reaching 20 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 27, 2021
Touchdown
7:15 PM CDT (00:15 UTC)
Path length
0.1 miles (0.2 km)
Path width
20 yards (18 m)
Deaths
0
Injuries
0
County
Tillman County
Touchdown point
34.210, -98.890
Lift-off point
34.210, -98.890
Record number
2104271815-01

What the Weather Service recorded

A slow moving trough and a dryline helped initiate convection during the afternoon of the 27th. Numerous hail and wind reports were received, along with a few reports of tornadoes.

A storm chaser observed a brief tornado estimated to be about 9 miles south of Hollister. No damage was reported.

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

The warnings

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 severe thunderstorm watch, issued at 18:57 UTC and running to 01:25 UTC.

Issued (UTC)ExpiredProductOffice
18:57 UTC01:25 UTCSevere Thunderstorm WatchOUN
22:30 UTC23:15 UTCSevere Thunderstorm WarningOUN
23:01 UTC23:45 UTCSevere Thunderstorm WarningOUN
23:12 UTC23:37 UTCSevere Thunderstorm WarningOUN
23:41 UTC00:30 UTCSevere Thunderstorm WarningOUN
00:15 UTC01:00 UTCSevere Thunderstorm WarningOUN
00:19 UTC01:00 UTCTornado WarningOUN
00:53 UTC01:45 UTCSevere Thunderstorm WarningOUN
01:10 UTC02:00 UTCSevere Thunderstorm WarningOUN
01:25 UTC08:00 UTCSevere Thunderstorm WatchOUN
03:24 UTC03:52 UTCFlood WatchOUN

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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:49 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.

Norman, OK (KOUN), 00:00Z

0.3 hours before the tornado, 177 km from the path. April 28, 2021.

Skew-T log-pSkew-T log-p diagram, Norman, OK at 00:00Z on 2021-04-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 661 joules per kilogram, CIN -196, lifted condensation level 1104 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, Norman, OK at 00:00Z on 2021-04-28The 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 228 square meters per square second, 0 to 6 km bulk shear 50 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
661 J/kg
Mixed-layer CIN
-196 J/kg
Surface CAPE
1562 J/kg
Mixed-layer LCL
1104 m above ground
0-6 km bulk shear
50 kt
0-1 km bulk shear
29 kt
0-1 km storm-relative helicity
228 m²/s²
0-3 km storm-relative helicity
198 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.0
0-3 km lapse rate
6.4 K/km

Open this sounding in Storm Lab

The radar

The Altus AFB radar (KFDR), 19 km away, was scanning. The volume nearest the touchdown began at 00:12 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
00:17 UTCFUNNEL CLOUD6 Sw LovelandTillman, OK
00:35 UTCTSTM WND GST 633 W GrandfieldTillman, OK

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

This ground now

The live radar over the trackEvery 2021 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are

The other tornadoes of April 27, 2021

13 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 272:32 PM MDTEF0Lincoln, CO0.050
April 273:49 PM CDTEF3Knox, TX8.4400$70,000
April 273:57 PM MDTEF0Lincoln, CO0.050
April 274:08 PM MDTUnratedCheyenne, CO0.850
April 274:08 PM MDTUnratedCheyenne, CO2.0100
April 274:15 PM MDTUnratedCheyenne, CO2.075
April 274:16 PM MDTUnratedCheyenne, CO4.0300
April 274:28 PM MDTUnratedCheyenne, CO1.3100
April 274:54 PM MDTUnratedCheyenne, CO4.550
April 275:27 PM MDTUnratedCheyenne, CO1.975
April 277:19 PM CDTUnratedWilbarger, TX0.230
April 277:47 PM CDTEF0Scurry, TX2.650
April 2712:00 AM CDTEF1Garvin, OK4.5150$30,000

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.