F1 tornado, Greencastle to St Thomas, 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

7:28 PM EDT (23:28 UTC)

Path length

2.5 miles (4.0 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

County

Franklin County

Touchdown point

39.880, -77.830

Lift-off point

39.880, -77.830

Record number

552

A survey team from the National Weather Service confirmed a tornado in Franklin County. The tornado occurred near the town of Greencastle and was rated an F1 on the Fujita scale. Wind speeds were estimated to be near 80 mph. The tornado first hit the ground about 2 miles to the southwest of Greencastle and moved to the north-northwest for about 2 miles. The width of the storm was approximately 30 yards. The tornado touched down at approximately 714 pm EDT and lifted at approximately 717 pm EDT. The tornado caused many trees to fall and damaged several structures. There were no injuries or deaths.

A survey team from the National Weather Service confirmed a tornado in Franklin County.The tornado occurred near the town of Saint Thomas and was rated an F1 on the Fujita scale. Top wind speeds were estimated at about 85 mph. The path was 2.5 miles long and began 3 miles south-southwest of Saint Thomas. The width of this tornado was 30 yards. The tornado touched down approximately at 728 pm EDT and lifted at 732 pm EDT. This tornado caused many trees to fall and damaged several structures.

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

8 minutes of warning. NWS CTP issued a tornado warning for this county at 23:20 UTC, 8 minutes before the tornado touched down, in force until 00:00 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, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 19:53 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.

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.

Hagerstown Regional (HGR), 21 km from the path, in the two hours either side.

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

The Sterling radar (KLWX), 105 km away, was scanning. The volume nearest the touchdown began at 23:29 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.