Tornadoes · United States · Pennsylvania · 2004
F1 tornado, Harrisburg to Hummelstown, Pennsylvania, August 4, 2004
From Harrisburg to Hummelstown, this F1 tornado ran 2.0 miles across Dauphin County on August 4, 2004, touching down at 6:12 PM EDT and reaching 400 yards wide. It killed nobody, and did $200,000 of property damage.
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 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
F173 to 112 mphthis tornado
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
- F1
- Date
- August 4, 2004
- Touchdown
- 6:12 PM EDT (22:12 UTC)
- Path length
- 2.0 miles (3.2 km)
- Path width
- 400 yards (366 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $200,000
- County
- Dauphin County
- Touchdown point
- 40.270, -76.780
- Lift-off point
- 40.270, -76.780
- Record number
- 419
What the Weather Service recorded
Thunderstorms spawned an F1 tornado during the late afternoon of Wednesday August 4th in western Dauphin County. The tornado first touched down near the intersection of Walnut and Brisban streets, in Paxtang. The tornado traveled east approximately 2 miles, and lifted near the intersection of Paxton Street and US Highway 322. Peak winds were estimated at 80 to 90 mph. There were no injuries or deaths.The tornado knocked down hundreds of trees, several falling on homes and cars.
Thunderstorms spawned a weak F1 tornado during the late afternoon of Wednesday August 4th in south central Dauphin County. The tornado first touched down in a field west of Swatara Creek about 2 miles south of Hummelstown. The tornado traveled east approximately 2 miles, and lifted near Raleigh road. Peak winds were estimated at 85 mph. There were no injuries or deaths.The tornado knocked down dozens of trees, several falling on houses. Several homes were uninhabitable due to the damage.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
10 minutes of warning. NWS CTP issued a tornado warning for this county at 22:02 UTC, 10 minutes before the tornado touched down, in force until 22:45 UTC.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 21:25 UTC | 22:30 UTC | Severe Thunderstorm Warning | CTP |
| 22:02 UTC | 22:45 UTC | Tornado Warning | CTP |
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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 20:02 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 surface observations
Harrisburg/Capital (CXY), 8 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 21:56 UTC | 85 | 70 | 140° 11 kt | 1004.7 | ||
| 22:13 UTC | 77 | 71.6 | 330° 20 kt | 32 | 1006.8 | -RA SQ |
| 22:16 UTC | 73.4 | 71.6 | 350° 14 kt | 32 | 1006.8 | +RA BR SQ |
| 22:26 UTC | 69.8 | 69.8 | 320° 14 kt | 25 | 1008.1 | +RA BR |
| 22:29 UTC | 71.6 | 71.6 | 350° 13 kt | 22 | 1007.8 | +RA BR |
| 22:34 UTC | 71.6 | 71.6 | 310° 10 kt | 22 | 1008.1 | +RA BR |
| 22:36 UTC | 71.6 | 71.6 | 320° 10 kt | 22 | 1008.1 | +RA BR |
| 22:39 UTC | 71.6 | 71.6 | 310° 6 kt | 1007.8 | +RA BR | |
| 22:48 UTC | 71.6 | 71.6 | 3 kt | 1007.5 | RA BR | |
| 22:56 UTC | 72 | 72 | 40° 5 kt | 1006.4 | -RA BR | |
| 23:09 UTC | 71.6 | 71.6 | 0° 0 kt | 1006.8 | -RA | |
| 23:25 UTC | 73.4 | 71.6 | 0° 0 kt | 1006.8 | ||
| 23:56 UTC | 73 | 72 | 0° 0 kt | 1006.4 |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The State College radar (KCCX), 126 km away, was scanning. The volume nearest the touchdown began at 22:12 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.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 22:15 UTC | TSTM WND DMG | Carlisle | Cumberland, PA | SEVERAL TREES DOWN ALONG BELVEDERE AVENUE |
| 22:20 UTC | TSTM WND DMG | Harrisburg | Dauphin, PA | SEVERAL TREES DOWN ON 14TH AND MARKET STREET...ALSO ON FRONT STREET. |
| 22:20 UTC | TSTM WND DMG | Newville | Cumberland, PA | STRUCTORAL DAMAGE |
| 22:20 UTC | FLASH FLOOD | York | York, PA | SEVERAL ROADS FLOODED COUNTY WIDE |
| 22:28 UTC | TSTM WND DMG | 1 N Colonial Park | Dauphin, PA | SEVERAL TREES DOWN AT INTERSECTION OF HIGHWAY 322 AND HIGHWAY 83 |
| 22:30 UTC | TSTM WND DMG | 7 Se New Cumberland | York, PA | STRUCTORAL DAMAGE SHEEPBRIDGE ROAD...POTENTIAL TORNADO |
| 22:55 UTC | TSTM WND DMG | Lititz | Lancaster, PA | SEVERAL TREES DOWN AND WIRES DOWN. |
| 23:00 UTC | TSTM WND DMG | York | York, PA | SEVERAL TREES DOWN THROUGHOUT COUNTY. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2004 tornado in PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are
The other tornadoes of August 4, 2004
8 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| August 4 | 10:16 AM EST | F0 | Monroe, IN | 0.1 | 10 | $1,000 | ||
| August 4 | 1:50 PM EDT | F0 | Brevard, FL | 2.0 | 30 | |||
| August 4 | 3:35 PM EDT | F0 | Westmoreland, PA | 0.1 | 30 | $1,000 | ||
| August 4 | 6:07 PM EDT | F0 | Cumberland, PA | 1.0 | 75 | $20,000 | ||
| August 4 | 6:12 PM EDT | F1 | Cumberland, PA | 2.5 | 125 | $50,000 | ||
| August 4 | 6:20 PM EDT | F1 | Dauphin, PA | 2.0 | 200 | $100,000 | ||
| August 4 | 6:45 PM EDT | F0 | Lancaster, PA | 2.0 | 100 | $10,000 | ||
| August 4 | 7:04 PM EDT | F0 | York, PA | 0.8 | 25 |
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.