Tornadoes · United States · Oklahoma · 2017
Unrated tornado, Frederick Arpt to Grandfield, Oklahoma, May 10, 2017
From Frederick Arpt to Grandfield, this Unrated tornado ran 0.3 miles across Tillman County on May 10, 2017, touching down at 8:31 PM CDT 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.
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 mph
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.
Unratedthis tornado
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
- Unrated
- Date
- May 10, 2017
- Touchdown
- 8:31 PM CDT (01:31 UTC)
- Path length
- 0.3 miles (0.5 km)
- Path width
- 50 yards (46 m)
- Deaths
- 0
- Injuries
- 0
- County
- Tillman County
- Touchdown point
- 34.302, -98.679
- Lift-off point
- 34.302, -98.679
- Record number
- 1705101931-01
What the Weather Service recorded
With outflow boundaries floating around the state and a large upper low moving into the region, scattered storms formed across Oklahoma and western north Texas on the evening of the 10th.
Storm chasers observed a brief tornado about 7 miles east-northeast of Davidson. No damage was reported and the location was estimated.
A tornado was observed by numerous storm chasers crossing State Highway 36 east of Loveland and north of Grandfield. No damage was reported.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
0 minutes of warning. NWS OUN issued a tornado warning for this county at 01:31 UTC, 0 minutes before the tornado touched down, in force until 01:46 UTC.
The county was under a tornado watch, issued at 19:43 UTC and running to 03:00 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 19:43 UTC | 03:00 UTC | Tornado Watch | OUN |
| 22:14 UTC | 22:30 UTC | Severe Thunderstorm Warning | OUN |
| 23:54 UTC | 00:45 UTC | Severe Thunderstorm Warning | OUN |
| 00:20 UTC | 01:00 UTC | Severe Thunderstorm Warning | OUN |
| 00:36 UTC | 01:30 UTC | Severe Thunderstorm Warning | OUN |
| 00:45 UTC | 01:45 UTC | Flood Advisory | OUN |
| 00:55 UTC | 01:30 UTC | Tornado Warning | OUN |
| 01:28 UTC | 02:00 UTC | Severe Thunderstorm Warning | OUN |
| 01:31 UTC | 01:46 UTC | Tornado 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 01:00 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 May 10, 6:56 PM CDT, 1 hour 35 minutes earlier.
Area forecast discussion, May 10, 6:56 PM CDT, 1 hour 35 minutes before
Area Forecast Discussion National Weather Service Norman OK 656 PM CDT Wed May 10 2017 .DISCUSSION... Severe thunderstorm and heavy rainfall potential continues this evening mainly across southwestern Oklahoma. Latest radars as of 650 pm depicted numerous showers and thunderstorms near an old outflow boundary from Quanah Texas to Altus to Fort Cobb. Think storms will continue near this boundary. Some storms will likely be severe with large hail and damaging winds as the main hazard. Training of storms may lead to heavy rainfall of 1 to 3 inches and localized flooding as well as the air is moist (precipitable water values 1.2-1.7", well above average for this time of year). These storms will move into the Oklahoma City metro area between 730 pm and midnight, but overall, are expected to weaken as the air is cooler and more stable across central Oklahoma (MLCAPE 500-1500 J/kg) compared to southwestern Oklahoma and western north Texas (MLCAPE 1500-2500 J/kg). Still cannot rule out some severe hail and wind reports as well as heavy rainfall and localized flooding. Northwest of the outflow boundary appears to have a lower severe potential tonight due to cooler and more stable air in place. Southeast of the outflow boundary may remain too capped for storm development this evening. It appears the threat for tornadoes may be decreasing in many areas this evening. Latest storms appear mainly be northwest and located on the cooler side of the outflow boundary. Low level shear will be increasing over the next few hours however, so will continue to monitor, especially near the Lawton, Wichita Falls, and Vernon areas where the latest STP values were 2 to 3. Products will be updated shortly. Aviation discussion for the 00 UTC TAFs is below as well. MBS && .AVIATION... Have very low confidence in the TAFs. ISO-NUM TSRA will affect locations near KLTS-KOKC before 06 UTC and bring brief MVFR conditions as well as variable strong winds. Additional SHRA/TSRA may affect other sites as well and continue anytime now through Thursday night, but pinpointing when and where activity occurs remains very challenging. Widespread MVFR and lower conditions may form anywhere north of KLTS-KOUN before 18 UTC. Most places are expected to be MVFR or VFR after 18 UTC. A surface wind shift to the north will occur at many sites 09-22 UTC as a cold front moves south. MBS && .PREV DISCUSSION... /issued 155 PM CDT Wed May 10 2017/ DISCUSSION... Main focus is this afternoon and evening with potential for severe thunderstorms. Latest observations show an outflow from morning convection oriented east-northeast to west-southwest across the area, roughly from just south of Ponca City to near Kingfisher to just north of Hobart and Altus. North of the boundary, convection has been persistent. Latest water vapor band imagery shows deep closed low over central New Mexico early this afternoon, drifting slowly east. 7.3 micrometer band clearly shows deep EML plume moving north- northeast atop moist boundary layer. Moderate instability is expected from mid-late afternoon south of aforementioned outflow boundary, across extreme southwest Oklahoma and western north Texas. Deep moist boundary layer and meridional flow may not be favorable for significant eastward mixing of the dryline and latest short term model guidance support this. Backed low level flow that veers quickly above the surface as well relatively low LCLs will support low-level mesocyclones and a tornado threat. Significant CAPE in the hail growth zone and a tendency for supercell storm mode will support a threat of large to very large hail as well. Damaging winds are another convective threat. Thunderstorms should move northeast potentially reaching the I-35 corridor this evening. This will be the main area of convection today. Further north convection and a few marginally severe storms will be possible, but the air mass north of the boundary is comparatively more stable. We have shifted precipitation chances tomorrow further west based on trends. There is some uncertainty on how convection will evolve this evening and overnight, and this will have implications on tomorrow's forecast. Admittedly the majority of our attention has been on today and tonight's potential. But, there seems to be enough signal in model trends to bring thunderstorm chances further west, with afternoon convection (including the possibility of severe thunderstorms) certainly possible near I-35 and the metro. No significant chances were needed to latter portions of the forecast. Mean ridging should preclude convection through at least Sunday afternoon, but some isolated storms that develop in the panhandles (if they develop) may approach far western Oklahoma by evening. An ejecting shortwave trough across the central Rockies into the central and northern Plains early next week will lead to daily convective chances, and severe thunderstorms may be possible. We will refine timing, coverage and threats as smaller scale details become more clear during the next few days. BRB && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 65 80 57 73 / 90 60 40 10 Hobart OK 60 80 55 75 / 70 20 20 0 Wichita Falls TX 64 87 59 77 / 30 20 10 0 Gage OK 55 71 48 73 / 50 50 10 0 Ponca City OK 62 77 55 73 / 50 70 50 10 Durant OK 67 80 59 75 / 20 80 50 10 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && 17
Hazardous weather outlook, May 10, 8:26 PM CDT, 5 minutes before
Hazardous Weather Outlook...UPDATED National Weather Service Norman OK 826 PM CDT Wed May 10 2017 OKZ004>048-050>052-TXZ083>090-120130- 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- 826 PM CDT Wed May 10 2017 This hazardous weather outlook is for portions of northern... western...central...and southern Oklahoma...and western north Texas. .DAY ONE...Tonight... .Thunderstorms... There is a Slight Risk of severe thunderstorms across portions of Oklahoma and western north Texas tonight. .Location... The Slight Risk area is west of a line from Stillwater and Shawnee, to Pauls Valley and Ardmore, Oklahoma. .Timing... Severe storms will be possible through midnight tonight. .Impacts... Large hail up to the size of golf balls and damaging wind gusts up to 70 mph will be possible. A few tornadoes will also be possible, especially across portions of southwestern Oklahoma and western north Texas. .Discussion... Ongoing thunderstorms over central and southwestern Oklahoma and western north Texas will continue to pose a threat of severe weather through the remainder of the evening as they slowly move east and northeast. Large hail and strong winds will be the main concerns across the risk area. A few tornadoes will also be possible, especially near the outflow boundary in southwest Oklahoma and western north Texas where the air is most unstable. The potential for severe weather is expected to decrease after midnight tonight. .SPOTTER AND EMERGENCY MANAGEMENT STATEMENT.... Storm spotter groups and emergency management personnel across the risk area should remain alert for severe weather operations. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday... .Thunderstorms... There is a slight risk of severe thunderstorms Thursday afternoon and evening across portions of southeastern Oklahoma. Large hail, damaging winds, and perhaps a tornado or two will be possible. Thunderstorm chances will end late Thursday night across eastern and southeastern Oklahoma, then return Monday into early next week. Get graphics and more details at weather.gov/norman...and follow our weather forecast office on Twitter and Facebook. MBS
In the hours before
Local storm report, May 10, 7:11 PM CDT, 1 hour 20 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
711 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0708 PM HAIL 2 S ODELL 34.32N 99.42W
05/10/2017 E1.00 INCH WILBARGER TX TRAINED SPOTTER
&&
DWLocal storm report, May 10, 7:26 PM CDT, 1 hour 5 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
726 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0720 PM HAIL HEADRICK 34.63N 99.14W
05/10/2017 E1.00 INCH JACKSON OK TRAINED SPOTTER
&&
DWLocal storm report, May 10, 8:00 PM CDT, 31 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
800 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0758 PM HAIL FREDERICK 34.39N 99.01W
05/10/2017 E1.00 INCH TILLMAN OK TRAINED SPOTTER
&&
DWLocal storm report, May 10, 8:14 PM CDT, 17 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
814 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0805 PM TORNADO 6 E DAVIDSON 34.24N 98.97W
05/10/2017 TILLMAN OK STORM CHASER
&&
DWLocal storm report, May 10, 8:20 PM CDT, 11 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
820 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0804 PM TSTM WND GST 3 SE FREDERICK 34.36N 98.97W
05/10/2017 M72 MPH TILLMAN OK ASOS
&&
DWLocal storm report, May 10, 8:27 PM CDT, 4 minutes before
PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE NORMAN OK
827 PM CDT WED MAY 10 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0759 PM TSTM WND GST 3 SE FREDERICK 34.36N 98.97W
05/10/2017 M72.00 MPH TILLMAN OK ASOS
&&
DWThe 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
1.5 hours before the tornado, 155 km from the path. May 11, 2017.
- Mixed-layer CAPE
- 1639 J/kg
- Mixed-layer CIN
- -10 J/kg
- Surface CAPE
- 1961 J/kg
- Mixed-layer LCL
- 514 m above ground
- 0-6 km bulk shear
- 61 kt
- 0-1 km bulk shear
- 20 kt
- 0-1 km storm-relative helicity
- 175 m²/s²
- 0-3 km storm-relative helicity
- 136 m²/s²
- Significant tornado parameter
- 1.5
- Supercell composite
- 5.6
- 0-3 km lapse rate
- 5.5 K/km
Norman, OK (KOUN), 12:00Z
10.5 hours after it, 155 km from the path. May 11, 2017.
- Mixed-layer CAPE
- 592 J/kg
- Mixed-layer CIN
- -121 J/kg
- Surface CAPE
- 1785 J/kg
- Mixed-layer LCL
- 1262 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 106 m²/s²
- 0-3 km storm-relative helicity
- 91 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.8
- 0-3 km lapse rate
- 5.6 K/km
The radar
The Altus AFB radar (KFDR), 28 km away, was scanning. The volume nearest the touchdown began at 01:31 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 |
|---|---|---|---|---|
| 00:20 UTC | HAIL 1 | Headrick | Jackson, OK | |
| 00:58 UTC | HAIL 1 | Frederick | Tillman, OK | |
| 00:59 UTC | TSTM WND GST 72 | 3 Se Frederick | Tillman, OK | |
| 01:04 UTC | TSTM WND GST 72 | 3 Se Frederick | Tillman, OK | |
| 01:05 UTC | TORNADO | 6 E Davidson | Tillman, OK | |
| 01:29 UTC | TORNADO | 6 E Loveland | Tillman, OK | MEDIA CHASERS AND SPOTTERS REPORTED A TORNADO THAT CROSSED HIGHWAY 36. |
| 01:41 UTC | TORNADO | 7 Sse Chattanooga | Cotton, OK | FROM PENN STATE STORM CHASE TEAM. RADAR INDICATED THE TORNADO LIKELY MOVED NEAR THE TILLMAN-COTTON COUNTY LINE. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2017 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are
The other tornadoes of May 10, 2017
13 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| May 10 | 3:27 AM CDT | EF1 | Armstrong, TX | 2.8 | 180 | |||
| May 10 | 4:01 AM CDT | EF1 | Gray, TX | 2.6 | 50 | |||
| May 10 | 12:37 PM MDT | EF0 | Colfax, NM | 1.7 | 50 | |||
| May 10 | 2:46 PM CDT | EF0 | Van Buren, IA | 2.8 | 50 | |||
| May 10 | 2:54 PM CDT | Unrated | Motley, TX | 0.0 | 10 | |||
| May 10 | 3:37 PM CDT | Unrated | Cottle, TX | 0.0 | 10 | |||
| May 10 | 3:58 PM CDT | Unrated | Cottle, TX | 1.1 | 25 | |||
| May 10 | 4:44 PM CDT | Unrated | Hall, TX | 0.4 | 50 | |||
| May 10 | 7:49 PM CDT | EF0 | Macon, IL | 0.1 | 20 | $8,000 | ||
| May 10 | 8:05 PM CDT | EF0 | Tillman, OK | 0.3 | 30 | |||
| May 10 | 8:36 PM CDT | Unrated | Cotton, OK | 2.0 | 100 | |||
| May 10 | 10:58 PM CDT | Unrated | Val Verde, TX | 0.1 | 10 | |||
| May 10 | 12:34 AM CDT | EF0 | Newton, MO | 1.0 | 100 | $100,000 |
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.