F1 tornado, Mifflintown, Pennsylvania, September 17, 2004

1. F040 to 72 mph

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

2. F173 to 112 mphthis tornado

   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

F1

Date

September 17, 2004

Touchdown

9:10 PM EDT (01:10 UTC)

Path length

4.5 miles (7.2 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Juniata County

Touchdown point

40.620, -77.380

Lift-off point

40.620, -77.380

Record number

558

A survey team from the National Weather Service confirmed a tornado in Juniata County. A tornado touched down near the town of Denholm and was likely influenced by the steep terrain of the area. The damage, in the form of downed trees, could be easily seen from Route 333. About 100 trees were knocked down with this tornado. The path was approximately 1 mile long and about 75 yards wide. The tornado occurred around 905 pm EDT and lifted at 907 pm EDT. This tornado was rated F1 on the Fujita scale with winds approaching 85 mph.There were no known injuries or deaths.

A survey team from the National Weather Service confirmed a tornado in Juniata County. A tornado touched down near the town of Arch Rock. It downed trees which were visible along Township Road 527. The length of the tornado was approximately 4.5 miles and the width was about 100 yards. In addition to the tornado, downburst winds were also observed in a much wider swath. Damage was mainly confined to trees being knocked down, however several structures had minor damage and several corn fields were flattened. The tornado touched down at approximately 910 pm EDT and lasted until approximately 913 pm EDT. The tornado was rated F1 on the Fujita scale with winds estimated at 85 mph.There were no known injuries or deaths.

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

27 minutes of warning. NWS CTP issued a tornado warning for this county at 00:43 UTC, 27 minutes before the tornado touched down, in force until 01:30 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 General Thunderstorms Risk. The outlook in force was issued at 00:51 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.

State College (UNV), 47 km from the path, in the two hours either side.

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

The State College radar (KCCX), 62 km away, was scanning. The volume nearest the touchdown began at 01:10 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 2004 tornado in PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are

57 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.