F0 tornado, Gillette, Wyoming, June 21, 2003

1. F040 to 72 mphthis tornado

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. 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.

4. 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.

5. F4207 to 260 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. 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.

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.

Rating

F0

Date

June 21, 2003

Touchdown

2:25 PM MDT (20:25 UTC)

Path length

1.0 miles (1.6 km)

Path width

10 yards (9 m)

Deaths

0

Injuries

0

County

Campbell County

Touchdown point

44.280, -105.380

Lift-off point

44.280, -105.380

Record number

1219

A strong upper-level shortwave moving over northeastern Wyoming produced a long lived supercell thunderstorm. The thunderstorm developed over western Campbell County and moved east across Gillette and continued to Rozet. The storm continued into southern Crook County, moving just north of Moorcroft and Sundance. West of Gillette, the storm became tornadic and produced brief tornadoes. One tornado briefly touched down 12 miles west of Gillette in the vicinity of Force Road, north of Interstate 90, with no damage. Another tornado briefly touched down near the Wyodak Power Plant, about 5 miles east of Gillette, also with no damage. Golf ball to baseball sized hail was common across Campbell and Crook Counties. Extensive hail damage was reported in Gillette, particularly across northern parts of the city. Auto dealerships estimated losses of several million dollars. Insurance companies estimated claims totals from automobile and roof damage to be in the millions of dollars.

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

7 minutes of warning. NWS UNR issued a tornado warning for this county at 20:18 UTC, 7 minutes before the tornado touched down, in force until 21:15 UTC.

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 Storm Prediction Center had this point in a Slight Risk. The outlook in force was issued at 19:33 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.

NWS Rapid City, SD wrote its last area forecast discussion before the tornado touched down at Jun 21, 10:35 AM MDT, 3 hours 50 minutes earlier.

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1035 AM MDT SAT JUN 21 2003

AS OF 16Z...SLOW MOVING COLD FRONT STRETCHED FROM NEAR HEI TO EFC TO
EAST OF GCC. FRONT WILL CONTINUE TO SLOWLY MOVE EASTWARD ACROSS THE
REST OF THE CWA THIS AFT...REACHING FAR EASTERN CWA THIS EVE. MOST
NOTICIBLE WITH THE FRONT WILL BE THE DRIER AIR FILTERING IN BEHIND
WITH UPPER 40S TO LOWER 50S DEWPOINTS. SEVERAL PIECES OF SHRTWV
ENERGY ARE MOVING NORTHEASTWARD ACROSS THE REGION. ONE IS MOVING
ACROSS EASTERN NEB AND SD RIGHT NOW. ANOTHER IS MOVING ACROSS
EASTERN MT...WHILE YET ANOTHER IS MOVING INTO SOUTHWEST WY. HAVE
RAISED POPS A BIT IN NE WY AND THE HILLS FOR THE AFT AS THE WAVE IN
SOUTHWEST WY APPROACHES THIS AFT.

SPC SLIGHT RISK FOR SEVERE WX ACROSS ENTIRE CWA LOOKS APPROPRIATE
...THOUGH THINK SLIGHTLY BETTER CHANCES MAY END UP BEING IN THE
VICINITY OF THE BOUNDARY AS IT MOVES INTO CENTRAL SD LATER THIS AFT
AND THIS EVE. DEWPOINTS IN THE LOW TO MID 60S AND TEMPS NEAR 90 BY
LATE AFT WILL RESULT IN A VERY UNSTABLE ATMOS ACROSS SOUTH CENTRAL
SD WITH CAPES NEAR 2000 J/KG AND VERY STEEP LAPSE RATES. LATEST RUC
AND ETA SHOW STRONG LIFT DEVELOPING ALONG THE BOUNDARY BY 00Z. SHEAR
IS STRONG ENUF FOR ISOLATED SUPERCELLS. LARGE HAIL AND STRONG WINDS
WOULD BE THE MAIN THREATS AGAIN.

NOT MUCH IN THE WAY OF CHANGES MADE TO THE ZONES FOR TODAY. BUMPED
UP POPS IN NE WY AND THE HILLS...TWEEKED TEMPS UP A BIT IN A FEW
AREAS...AND ADJUSTED WINDS WHERE APPROPRIATE AS THE FRONT MOVES
THRU.

.UNR...NONE.

ST

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-221230-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RAPID CITY SD
659 AM MDT SAT JUN 21 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN SOUTH DAKOTA AND
NORTHEASTERN WYOMING.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER NORTHEASTERN
WYOMING AND WESTERN SOUTH DAKOTA THIS AFTERNOON AND EVENING.
THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND CONTINUE INTO THE
EVENING. SOME STRONGER STORMS MAY BECOME ORGANIZED AND PRODUCE
SEVERE WEATHER. THE PRIMARY THREAT WILL BE HAIL LARGER THAN 3/4 INCH
DIAMETER.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A DAILY CHANCE FOR SHOWERS AND THUNDERSTORMS ARE EXPECTED SATURDAY
THROUGH THURSDAY AS A SERIES OF DISTURBANCES MOVES ACROSS THE
NORTHERN PLAINS. THERE IS A SLIGHT CHANCE FOR SEVERE STORMS SATURDAY
AS A COLD FRONT WILL BE MOVING THROUGH NORTHEAST WYOMING AND WESTERN
SOUTH DAKOTA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY.

99

In the hours before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
214 PM MDT SAT JUN 21 2003

TIME(MDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0143 PM    15 WNW GILLETTE           WY   TORNADO
06/21/03   CAMPBELL                       REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.

0155 PM    8 W GILLETTE              WY   TORNADO
06/21/03   CAMPBELL                       REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.
                                          TORNADO WAS ON THE
                                          GROUND EARLIER, AND
                                          BROKE UP AROUND 155 PM
                                          MDT.

0204 PM    8 W GILLETTE              WY   1.75 INCH HAIL
06/21/03   CAMPBELL                       REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.

0209 PM    GILLETTE                  WY   1.75 INCH HAIL
06/21/03   CAMPBELL                       REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL ON
                                          NORTHWEST SIDE OF TOWN.

Bunkers

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.

Gillette (GCC), 15 km from the path, in the two hours either side.

From the Iowa Environmental Mesonet's archive of airport observations.

The live radar over the trackEvery 2003 tornado in WyomingEvery tornado in Wyoming since 1950Warnings in force in Wyoming nowThe forecast where you are

4 more were confirmed in the United States that day.

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.