Tornadoes · United States · Oklahoma · 2020
EF1 tornado, Marlow, Oklahoma, April 21, 2020
This EF1 tornado ran 1.6 miles across Stephens County on April 21, 2020, touching down at 11:43 PM CDT and reaching 100 yards wide. It killed nobody, and did $75,000 of property damage.
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.
EF065 to 85 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mphthis tornado
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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
- EF1
- Date
- April 21, 2020
- Touchdown
- 11:43 PM CDT (04:43 UTC)
- Lifted
- 11:46 PM CDT (04:46 UTC)
- On the ground
- 3 minutes
- Path length
- 1.6 miles (2.6 km)
- Path width
- 100 yards (91 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $75,000
- County
- Stephens County
- Touchdown point
- 34.668, -97.974
- Lift-off point
- 34.662, -97.947
- Record number
- 2004212243-01
What the Weather Service recorded
Storms initiated along a warm front amid strong instability and enough shear for multiple storms producing very large hail up to the size of baseballs and a few brief tornadoes on the evening of the 21st.
A tornado developed just northwest of the city limits of Marlow and moved east-southeast into far northern portions of the city of Marlow. Near the beginning of the tornado, numerous buildings on a farm on the north side of Ballpark Road were heavily damaged, including most of the roof off of a home and an outbuilding. The tornado moved east-southeast breaking large trees and utility poles along Ballpark Road. A number of trees were damaged at the Marlow cemetery on the northeast side of Marlow.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
15 minutes of warning. NWS OUN issued a tornado warning for this county at 04:28 UTC, 15 minutes before the tornado touched down, in force until 05:00 UTC.
The county was under a severe thunderstorm watch, issued at 23:50 UTC and running to 06:48 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 23:50 UTC | 06:48 UTC | Severe Thunderstorm Watch | OUN |
| 03:54 UTC | 05:00 UTC | Severe Thunderstorm Warning | OUN |
| 04:28 UTC | 05:00 UTC | Tornado Warning | OUN |
| 04:47 UTC | 05:30 UTC | Severe Thunderstorm Warning | OUN |
| 04:48 UTC | 05:45 UTC | Severe Thunderstorm Warning | OUN |
| 04:53 UTC | 05:45 UTC | Tornado Warning | OUN |
| 05:14 UTC | 05:45 UTC | Severe Thunderstorm Warning | OUN |
| 05:16 UTC | 05:43 UTC | Tornado Warning | OUN |
| 05:26 UTC | 05:57 UTC | Severe Thunderstorm Warning | OUN |
| 05:33 UTC | 06:30 UTC | Severe Thunderstorm Warning | OUN |
| 05:44 UTC | 06:30 UTC | Severe Thunderstorm Warning | OUN |
| 06:26 UTC | 07:15 UTC | Severe Thunderstorm Warning | OUN |
| 06:48 UTC | 07:38 UTC | Severe Thunderstorm Watch | OUN |
| 13:33 UTC | 14:15 UTC | Severe Thunderstorm Warning | OUN |
| 13:53 UTC | 19:34 UTC | Severe Thunderstorm Watch | OUN |
| 19:34 UTC | 22:00 UTC | Tornado Watch | OUN |
| 20:38 UTC | 21:11 UTC | Severe Thunderstorm Warning | OUN |
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 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 00:43 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.
What forecasters said that day
The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Norman, OK wrote its last area forecast discussion before the tornado touched down at Apr 21, 6:34 PM CDT, 5 hours 9 minutes earlier.
Area forecast discussion, Apr 21, 6:34 PM CDT, 5 hours 9 minutes before
Area Forecast Discussion National Weather Service Norman OK 634 PM CDT Tue Apr 21 2020 ...New AVIATION... .SHORT TERM... (This evening through Wednesday) Issued at 213 PM CDT Tue Apr 21 2020 Satellite imagery is beginning to show signs of lift now increasing ahead of an initial mid level shortwave trough that will move out of the TX panhandle late this afternoon through tonight. Convective initiation should occur somewhere within the next hour or two near NW OK and the northern TX panhandle. A few storms may also try to develop on the southern flank of the mid level moisture moisture plume extending from NW OK into ESE OK into this evening. Some cumulus are now evident in vis imagery within this plume. The most likely scenario still appears to be a small cluster of storms coming off the high plains and tracking eastward across northern OK, with 1- 2 discrete elevated supercells south of it moving into portions of central OK late tonight. Steep lapse rates within the hail growth zone could support around a 3-6 hour window of very large hail within the supercells. As the first, smaller cluster of storms moves out of our area and dissipates to the east late tonight/early Wed AM, the main mid level vort max will begin to move in from the west. Therefore, expect more widespread convection to begin around 12-15Z Wed especially along and north of I-40 as mid to upper ascent overspreads the region. These elevated storms will still have the potential to produce large hail up to the size of golf balls or larger near and just after sunrise. At the surface, a surface low will near the I-35 corridor around 18-21Z Wed, with an associated dryline and Pacific front. Instability should have the chance to ramp up ahead of these features early tomorrow afternoon within the warm sector over the SE 1/4 of OK. Surface based supercells will be possible within the aforementioned area Wed afternoon, with all severe weather threats possible into early Wed evening. && .LONG TERM... (Wednesday night through next Monday) Issued at 213 PM CDT Tue Apr 21 2020 Showers and thunderstorms and the potential for severe storms are expected to end Wednesday evening. Another round of showers and thunderstorms will then be possible Thursday night into Friday as a shortwave moves across the central/southern Plains and a cold front moves across the area. Models show NW flow will develop aloft over the region next week. Models also show another front moving across the area early next week, although there are some differences in timing. Some showers and thunderstorms could be possible with this boundary. Temperatures are expected to remain generally below but near the average mark into this weekend, with the coolest day expected to be Friday. Warmer temperatures, above average, will then be possible early next week. && .AVIATION... (00Z TAFS) Issued at 631 PM CDT Tue Apr 21 2020 VFR/MVFR ceilings are expected. A few models show that IFR ceilings could be possible at a few locations Wednesday morning. Thunderstorms will be possible off and on later this evening through Wednesday afternoon. Variable gusty winds and hail could be possible near/with some of the storms. A front will move across portions of the area Wednesday causing winds to shift towards the N and NW. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 61 69 53 78 / 80 80 20 0 Hobart OK 61 73 51 81 / 50 50 10 0 Wichita Falls TX 63 81 54 82 / 40 50 0 0 Gage OK 54 67 47 81 / 90 80 0 0 Ponca City OK 59 65 52 77 / 90 90 30 0 Durant OK 61 75 56 79 / 30 90 20 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && SHORT TERM...03 LONG TERM....25 AVIATION...25
Hazardous weather outlook, Apr 21, 9:17 PM CDT, 2 hours 26 minutes before
Hazardous Weather Outlook...UPDATED National Weather Service Norman OK 917 PM CDT Tue Apr 21 2020 OKZ004>048-050>052-TXZ083>090-230230- Harper-Woods-Alfalfa-Grant-Kay-Ellis-Woodward-Major-Garfield- Noble-Roger Mills-Dewey-Custer-Blaine-Kingfisher-Logan-Payne- Beckham-Washita-Caddo-Canadian-Oklahoma-Lincoln-Grady-McClain- Cleveland-Pottawatomie-Seminole-Hughes-Harmon-Greer-Kiowa-Jackson- Tillman-Comanche-Stephens-Garvin-Murray-Pontotoc-Coal-Cotton- Jefferson-Carter-Johnston-Atoka-Love-Marshall-Bryan-Hardeman- Foard-Wilbarger-Wichita-Knox-Baylor-Archer-Clay- 917 PM CDT Tue Apr 21 2020 This hazardous weather outlook is for portions of northern... western...central...and southern Oklahoma...and western north Texas. .DAY ONE...Through Tonight... .Thunderstorms... Strong to severe thunderstorms are expected to continue this evening and overnight, especially across western into central Oklahoma. Large hail up to the size of baseballs is the primary hazard. Wind gusts of 60 to 70 mph are also possible. .DAYS TWO THROUGH SEVEN...Wednesday through Monday... .Thunderstorms... Thunderstorms will continue to be possible through the day Wednesday. Some strong to severe thunderstorms, primarily with a large hail up to the size of golf balls and damaging wind threat, could occur during the morning hours across any portion of the area. By Wednesday afternoon, the severe storm threat will continue to progress eastward but is not expected to exit the area until evening. Storm intensity could be higher during the afternoon and evening hours, especially near and east of I-35 and south of I-44. The primary threats during the afternoon will continue to be large hail up to the size of baseballs and damaging winds. However, there is also a potential for some tornadoes, especially in areas southeast of a Seminole and Pauls Valley, to Marietta Oklahoma line. There are some uncertainties with the afternoon and evening activity due to effects from the storms later tonight into Wednesday morning so check for the latest information. Thunderstorms will also be possible Thursday night into Friday. The chance of severe weather with this activity looks to be low. Get graphics and more details at weather.gov/norman...and follow our weather forecast office on Twitter and Facebook. Mahale
In the hours before
Local storm report, Apr 21, 11:15 PM CDT, 28 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1115 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1112 PM TSTM WND GST 2 WNW ELGIN 34.79N 98.32W
04/21/2020 E60 MPH COMANCHE OK TRAINED SPOTTER
&&
SCLocal storm report, Apr 21, 11:16 PM CDT, 27 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1116 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1115 PM HAIL 2 E ELGIN 34.78N 98.26W
04/21/2020 E1.75 INCH COMANCHE OK AMATEUR RADIO
&&
SCLocal storm report, Apr 21, 11:21 PM CDT, 22 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1121 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1119 PM HAIL 3 E STERLING 34.75N 98.12W
04/21/2020 E1.75 INCH COMANCHE OK TRAINED SPOTTER
&&
SCLocal storm report, Apr 21, 11:22 PM CDT, 21 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1122 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1122 PM HAIL 2 NNE COOPERTON 34.89N 98.86W
04/21/2020 E2.00 INCH KIOWA OK TRAINED SPOTTER
&&
SCLocal storm report, Apr 21, 11:25 PM CDT, 18 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1125 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1125 PM HAIL STERLING 34.75N 98.17W
04/21/2020 E2.00 INCH COMANCHE OK TRAINED SPOTTER
&&
SCLocal storm report, Apr 21, 11:31 PM CDT, 12 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
1131 PM CDT TUE APR 21 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1129 PM HAIL 2 WNW BURKBURNETT 34.09N 98.60W
04/21/2020 E1.00 INCH WICHITA TX TRAINED SPOTTER
&&
SCThe 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
4.7 hours before the tornado, 80 km from the path. April 22, 2020.
- Mixed-layer CAPE
- 46 J/kg
- Mixed-layer CIN
- -146 J/kg
- Surface CAPE
- 592 J/kg
- Mixed-layer LCL
- 2104 m above ground
- 0-6 km bulk shear
- 71 kt
- 0-1 km bulk shear
- 7 kt
- 0-1 km storm-relative helicity
- 18 m²/s²
- 0-3 km storm-relative helicity
- 279 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.1
- 0-3 km lapse rate
- 8.1 K/km
Norman, OK (KOUN), 12:00Z
7.3 hours after it, 80 km from the path. April 22, 2020.
- Mixed-layer CAPE
- 20 J/kg
- Mixed-layer CIN
- -449 J/kg
- Surface CAPE
- 99 J/kg
- Mixed-layer LCL
- 1138 m above ground
- 0-6 km bulk shear
- 65 kt
- 0-1 km bulk shear
- 28 kt
- 0-1 km storm-relative helicity
- 375 m²/s²
- 0-3 km storm-relative helicity
- 455 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.5
- 0-3 km lapse rate
- 4.1 K/km
The radar
The Norman radar (KTLX), 97 km away, was scanning. The volume nearest the touchdown began at 04:44 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) | Report | Where | County | Remark |
|---|---|---|---|---|
| 03:32 UTC | HAIL 1.75 | Pocasset | Grady, OK | |
| 03:47 UTC | HAIL 2 | 2 N Amber | Grady, OK | REPORT FROM MPING. |
| 03:47 UTC | HAIL 2.5 | 1 S Pocasset | Grady, OK | |
| 04:11 UTC | HAIL 3 | Elgin | Comanche, OK | |
| 04:12 UTC | TSTM WND GST 60 | 2 Wnw Elgin | Comanche, OK | |
| 04:15 UTC | HAIL 1.75 | 2 E Elgin | Comanche, OK | |
| 04:19 UTC | HAIL 1.75 | 3 E Sterling | Comanche, OK | |
| 04:25 UTC | HAIL 2 | Sterling | Comanche, OK | |
| 04:40 UTC | TSTM WND DMG | 1 N Marlow | Stephens, OK | LARGE TREES DOWN AND POWER LINES DOWN. TIME BASED ON RADAR. |
| 04:47 UTC | HAIL 1.5 | Meers | Comanche, OK | |
| 04:57 UTC | HAIL 1 | 3 E Walters | Cotton, OK | |
| 05:04 UTC | HAIL 1 | 6 S Sterling | Comanche, OK | |
| 05:10 UTC | TSTM WND GST 60 | 7 Nw Velma | Stephens, OK | |
| 05:10 UTC | HAIL 1 | Medicine Park | Comanche, OK | |
| 05:15 UTC | HAIL 1.25 | Duncan | Stephens, OK | |
| 05:17 UTC | HAIL 1.75 | Duncan | Stephens, OK | |
| 05:18 UTC | HAIL 1.25 | Duncan | Stephens, OK | |
| 05:33 UTC | HAIL 0.88 | Ratliff City | Carter, OK | |
| 06:20 UTC | HAIL 1.75 | Duncan | Stephens, OK | RELAYED VIA TWITTER |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2020 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are
The other tornadoes of April 21, 2020
2 more were confirmed in the United States that day.
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.