F0 tornado, Park Grove, Montana, July 8, 2002

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

July 8, 2002

Touchdown

7:40 PM MDT (01:40 UTC)

Path length

0.5 miles (0.8 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Property damage

$100,000

County

Valley County

Touchdown point

48.020, -106.400

Lift-off point

48.020, -106.400

Record number

785

A small tornado along the edge of a gust front damaged two modular homes and downed several trees in Park Grove. Many homes had some damage to awnings, and gutters and roofs.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

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 Moderate Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 00:34 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 Glasgow, MT wrote its last area forecast discussion before the tornado touched down at Jul 8, 2:40 PM MDT, 5 hours earlier.

NORTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
240 PM MDT MON JUL 8 2002

.SHORT TERM...SEVERE WATCH BOX INCLUDES WESTERN 4 COUNTIES.  EXPECT
THE COLD FRONT TO GENERATE ENOUGH DYNAMIC MIX TO GENERATE STRONG
THUNDERSTORMS.  FRONT IS MOVING RAPIDLY EAST AND WILL COMPLETELY
CROSS THE CWA BY LATE EVENING.  THETA E RIDGE AND CAPE GRADIENTS ARE
CONCENTRATED OVER THE CWA.  30+ KT LOW LEVEL JET CONTINUING STRONG
SOUTHEAST FLOW INTO THE CWA.  LAKE WIND ADVISORY WILL CONTINUE THIS
EVENING BECAUSE OF PROXIMITY TO CONVECTION OUTFLOW AND LOW LEVEL JET.

19Z SOUNDING SHOWING SOUTHEAST FLOW THROUGH 725MB BETWEEN 25-35
KTS.  ABOVE 725MB FLOW VEERS TO SOUTHWEST FOR REMAINDER OF
SOUNDING.  CAPE APPEARS LARGER THAN 12Z SOUNDING.  AIR COLUMN IS
WETTER THAN THE MORNING SOUNDING AND HINTS AT A LAPSE RATE NEARLY
PARALLEL TO THE MOIST ADIABATS FOR THIS AFTERNOON.  CWA IS STILL
AHEAD OF THE COLD FRONT AND LEADING INSTABILITY.  INDICES ARE: 2800+
J/KG CAPE  -8 LI  1.41 PW  314 SWEAT  63 M/S MAX VERT VELOCITY  82F
CONV TEMP

CIRRUS BLOW OFF FROM THUNDERSTORMS WEST OF CWA IS BEGINNING TO REACH
GGW.  CU FIELDS ARE DEVELOPING OVER THE AREA AND SHOWING SIGNS OF
INCREASED INSTABILITY.

.LONG TERM...MEDIUM RANGE MODELS IN FAIR AGREEMENT SO WILL CONTINUE
WITH THE AVN/MRF SOLUTION.  RIDGE WILL DOMINATE FRIDAY AND
SATURDAY.  A STRONG LOW WILL PUSH THROUGH THE RIDGE SUNDAY WITH A
TRAILING COLD POOL LASTING INTO MONDAY.  LOOKING AT POTENTIAL
THUNDERSTORMS SUNDAY AND MONDAY.  MCNULTY

KGGW BBB 057/082 056/085 052/078 81810011
     BBBW 059/087 059/091 058/090 055/087 8100000466
KGDV BBB 063/084 056/084 051/077 81710011
     BBBW 056/090 060/092 061/089 055/091 8100001337

.GGW...LAKE WIND ADVISORY FOR FORT PECK LAKE TONIGHT.

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.

Glasgow International Airport (GGW), 27 km from the path, in the two hours either side.

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

The Glasgow radar (KGGW), 27 km away, was scanning. The volume nearest the touchdown began at 01:37 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.

The live radar over the trackEvery 2002 tornado in MontanaEvery tornado in Montana since 1950Warnings in force in Montana nowThe forecast where you are

5 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.