Tornadoes · United States · Oklahoma · 2001
F0 tornado, Grady County, Oklahoma, May 4, 2001
This F0 tornado ran 0.2 miles across Grady County on May 4, 2001, touching down at 7:05 PM CDT and reaching 25 yards wide. It killed nobody.
The rating scale
Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
F040 to 72 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
F2113 to 157 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.
F3158 to 206 mph
Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.
F4207 to 260 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
F5261 to 318 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
- F0
- Date
- May 4, 2001
- Touchdown
- 7:05 PM CDT (00:05 UTC)
- Path length
- 0.2 miles (0.3 km)
- Path width
- 25 yards (23 m)
- Deaths
- 0
- Injuries
- 0
- County
- Grady County
- Touchdown point
- 35.050, -97.930
- Lift-off point
- 35.050, -97.930
- Record number
- 813
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.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 23:07 UTC | 23:45 UTC | Severe Thunderstorm Warning | OUN |
| 23:43 UTC | 00:30 UTC | Severe Thunderstorm Warning | OUN |
| 00:24 UTC | 01:00 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. The outlook in force was issued at 20:05 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 4, 2:02 PM CDT, 5 hours 3 minutes earlier.
Area forecast discussion, May 4, 2:02 PM CDT, 5 hours 3 minutes before
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 202 PM CDT FRI MAY 4 2001 VERY ACTIVE WX PATTERN TO PERSIST ACROSS MUCH OF THE FORECAST AREA THRU THE WEEKEND. UPPER LOW TO OUR WEST HAS MOVED ONLY SLOWLY SEWD THRU THE PAST 24 HRS AND IS NOW LOCATED OVR NERN AZ. MEANWHILE.. UPPER LOW OVR BAJA HAS BEGUN TO SHEAR OUT AND IS ACCOMPANIED BY AN 80+ KT SPEED MAX NOSING INTO SW TEX ATTM. HAVE BEEN WATCHING THE SITUATION FOR THIS AFTERNOON/EVENING WITH INCREASING INTEREST ALL MORNING. PARAMETERS FOR A SVR WX EPISODE THIS EVENING APPEAR TO BE COMING TOGETHER ACROSS THE SRN SECTIONS OF THE FA ATTM. SUBTROPICAL SPEED MAX IS ENHANCING DEEP LAYER SHEAR..AND AS LOW LEVEL FLOW BACKS THRU THE AFTERNOON SHEAR WILL ONLY GET BETTER..ESP 0-1KM. DESPITE WEAKER LAPSE RATES..CAPES ARE APPROACHING 2000 J/KG WITH LOW BOUNDARY LAYER T/TD SPREADS. THIS ENVIRONMENT IS NOT THAT DISSIMILAR TO A FEW DAYS LAST OCTOBER THAT PRODUCED SEVERAL SMALL TORNADIC SUPERCELLS..AND WUDNT BE SURPRISED TO SEE SOMETHING SIMILAR TODAY. SEVERAL CELLS IN NC TEX ARE ALREADY EXHIBITING LOW LEVEL ROTATION IN EXCESS OF 40 KTS - AND LATEST KFDR VAD WIND PROFILE LOOKS TO BE VERY SUPPORTIVE OF SUPERCELLS. EXPECT CONVECTION TO EVOLVE INTO AN MCS THAT WILL SWEEP MUCH OF THE ERN 2/3 OF THE FA OVERNITE. SOME LOCALLY HEAVY RAINFALL IS LIKELY..BUT EXPECT HEAVIEST AMOUNTS TO THE EAST OF LAST NITE. MUCH OF CENTRAL OK HAS NOT SEEN MUCH RAIN FOR NEARLY 2 WEEKS AND SHUD BE ABLE TO HANDLE FARILY DECENT RAINS WITHOUT MUCH TROUBLE..SO DO NOT PLAN ON A FLASH FLOOD WATCH ATTM. WILL LIKELY LET WATCH FOR WRN CWA EXPIRE WITH AFTERNOON PACKAGE ISSUANCE. MORNING CONVECTION EXPECTED TO MOVE EAST OF THE AREA IN TIME TO ALLOW RECOVERY ON SAT AFTERNOON..AND AS UPPER SYSTEM BRUSHES ACROSS INSTABILITY AXIS SAT AFT/EVE..ANOTHER ROUND OF SVR IS LIKELY. /SEE LATEST SWODY2 FOR DETAILS/ 12Z ETA IS EVEN MORE DEFINITIVE THAN YDAY IN SWINGING A TRAILING SHORTWAVE TROF INTO THE SRN PLAINS SUN AFT/EVE..AND THIS LOOKS INCREASINGLY LIKE ROUND 3 FOR SVR AS FRONT/DRYLINE WILL STILL BE IN THE AREA WITH HEALTHY INSTABILITY YET AGAIN IN PLACE BY 00Z MON. FRONT FINALLY LOOKS TO CLEAR THE AREA ON MONDAY WITH LOW LEVEL RIDGING BUILDING INTO THE AREA. WE ARE STILL SOMEWHAT SKEPTICAL ON HOW FAR FRONT WILL BE ABLE TO PUSH SWD SINCE MEDIUM RANGE MODELS ALL HINT AT SOME SORT OF MID LEVEL TROFFING HANGING IN THE AREA FOR MUCH OF THE WEEK. SEEMS AS THOUGH TSTORM CHANCES WILL RETURN TO WRN SECTIONS THURS/FRI IN WEAK DRYLINE REGIME..AND MAY NEED TO MONITOR TUES/WED FOR POPS AS WELL IF MOISTURE DOES NOT GET SCOURED OUT CLEANLY BY FRONT ON MONDAY. MILLER FIRST CUT AT NUMBERS.. OKC 62 77 61 80 / + 60 70 40 HBR 60 80 58 83 / 60 40 60 40 SPS 61 80 62 84 / + 60 60 40 GAG 56 80 53 83 / 40 40 60 40 PNC 62 77 61 80 / + 60 60 40 DUA 64 77 64 79 / 60 80 60 60 .OUN... OK...NONE. TX...NONE.
In the hours before
Local storm report, May 4, 4:15 PM CDT, 2 hours 50 minutes before
LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
415 PM CDT FRI MAY 04 2001
TIME (CDT) .....CITY LOCATION.....STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0405 PM GRANDFIELD OK TORNADO
05/04/01 TILLMAN PD RPTD BRIEF TOUCHDOWN ON
WEST SIDE OF TOWN. TREE AND
POWER LINE DAMAGE.
TLLocal storm report, May 4, 5:19 PM CDT, 1 hour 46 minutes before
LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
519 PM CDT FRI MAY 4 2001
TIME (CDT) .....CITY LOCATION.....STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0512 PM 5 N COOKIETOWN OK .88 INCH HAIL
05/04/01 COTTON HAM RADIO REPORT
LANELocal storm report, May 4, 5:31 PM CDT, 1 hour 34 minutes before
LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
531 PM CDT FRI MAY 4 2001
TIME (CDT) .....CITY LOCATION.....STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0300 PM 3 NE OKLAUNION TX TORNADO
05/04/01 WILBARGER BRIEF TOUCHDOWN
SEVERAL TREES UPROOTED
SHED DESTROYED
b REPORTED BY VERNON FIRE
LANELocal storm report, May 4, 6:07 PM CDT, 58 minutes before
LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
607 PM CDT FRI MAY 4 2001
TIME (CDT) .....CITY LOCATION.....STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0536 PM 3 SE GERONIMO OK TORNADO
05/04/01 COMANCHE BRIEF TOUCHDOWN
HAM RADIO REPORT
0548 PM 4 SW PUMPKIN CENTER OK TORNADO
05/04/01 COMANCHE MULTI-VORTEX TORNADO
REPORTED BY BROADCAST
MEDIA
0600 PM HULEN OK 80 MPH WIND GUST
05/04/01 COTTON (ESTIMATED)
HAM RADIO REPORT
LANEThe 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
0.1 hours before the tornado, 52 km from the path. May 5, 2001.
- Mixed-layer CAPE
- 320 J/kg
- Mixed-layer CIN
- -24 J/kg
- Surface CAPE
- 568 J/kg
- Mixed-layer LCL
- 683 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 335 m²/s²
- 0-3 km storm-relative helicity
- 405 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 3.2
- 0-3 km lapse rate
- 5.9 K/km
Norman, OK (KOUN), 12:00Z
11.9 hours after it, 52 km from the path. May 5, 2001.
- Mixed-layer CAPE
- 101 J/kg
- Mixed-layer CIN
- 0 J/kg
- Surface CAPE
- 115 J/kg
- Mixed-layer LCL
- 456 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km bulk shear
- 17 kt
- 0-1 km storm-relative helicity
- 78 m²/s²
- 0-3 km storm-relative helicity
- 72 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 5.0 K/km
The surface observations
Chickasha Municipal Airport (CHK), 6 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 22:10 UTC | 66.2 | 66.2 | 130° 15 kt | 20 | 1009.8 | |
| 22:30 UTC | 69.8 | 68 | 130° 15 kt | 19 | 1009.8 | |
| 22:50 UTC | 69.8 | 68 | 130° 14 kt | 19 | 1009.8 | -RA |
| 23:10 UTC | 69.8 | 68 | 120° 14 kt | 20 | 1009.8 | -TSRA |
| 23:30 UTC | 69.8 | 69.8 | 130° 9 kt | 17 | 1009.8 | RA |
| 23:50 UTC | 68 | 68 | 120° 8 kt | 15 | 1009.5 | TSRA |
| 00:10 UTC | 66.2 | 66.2 | 190° 18 kt | 23 | 1009.8 | +TSRA |
| 00:30 UTC | 62.6 | 62.6 | 170° 15 kt | 23 | 1009.8 | -TSRA |
| 00:50 UTC | 62.6 | 62.6 | 170° 9 kt | 20 | 1009.8 | VCTSRA |
| 01:10 UTC | 62.6 | 62.6 | 130° 10 kt | 1009.5 | -TSRA | |
| 01:30 UTC | 60.8 | 60.8 | 120° 8 kt | 1009.8 | VCTSRA | |
| 01:50 UTC | 60.8 | 60.8 | 120° 7 kt | 1009.1 | -VCTSRA |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Norman radar (KTLX), 67 km away, was scanning. The volume nearest the touchdown began at 00:05 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.
This ground now
The live radar over the trackEvery 2001 tornado in OklahomaEvery tornado in Oklahoma since 1950Warnings in force in Oklahoma nowThe forecast where you are
The other tornadoes of May 4, 2001
12 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| May 4 | 4:05 PM CDT | F1 | Tillman, OK | 0.5 | 200 | 1 | $250,000 | |
| May 4 | 5:45 PM CDT | F0 | Richardson, NE | 0.1 | 40 | |||
| May 4 | 6:15 PM CDT | F0 | Johnson, NE | 0.1 | 40 | |||
| May 4 | 6:16 PM CDT | F0 | Andrew, MO | 20.0 | 30 | |||
| May 4 | 6:48 PM CDT | F0 | Nemaha, NE | 0.1 | 40 | |||
| May 4 | 6:48 PM CDT | F0 | Andrew, MO | 25.0 | 0 | |||
| May 4 | 7:20 PM CDT | F0 | Grady, OK | 0.7 | 50 | |||
| May 4 | 7:25 PM CDT | F0 | Nodaway, MO | 25.0 | 0 | |||
| May 4 | 7:43 PM CDT | F0 | Johnson, NE | 0.1 | 40 | |||
| May 4 | 8:42 PM CDT | F1 | Johnson, TX | 0.3 | 50 | $30,000 | ||
| May 4 | 9:43 PM CDT | F1 | Tarrant, TX | 8.0 | 150 | 2 | $5.0 million | |
| May 4 | 9:45 PM CDT | F1 | Johnson, TX | 2.8 | 50 | 1 | $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.