EF2 tornado, Oxford to Cochranville, Pennsylvania, September 1, 2021

1. EF065 to 85 mph

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

2. EF186 to 110 mph

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

3. EF2111 to 135 mphthis tornado

   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. EF3136 to 165 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. EF4166 to 200 mph

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

6. EF5over 200 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

EF2

Date

September 1, 2021

Touchdown

4:15 PM EDT (20:15 UTC)

Lifted

4:22 PM EDT (20:22 UTC)

On the ground

7 minutes

Path length

5.9 miles (9.5 km)

Path width

350 yards (320 m)

Deaths

0

Injuries

0

Property damage

$500,000

County

Chester County

Touchdown point

39.770, -75.970

Lift-off point

39.850, -75.930

Record number

2109011415-01

15 damage points were recorded along this path by NWS PHI, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF2. The highest wind the damage implies is 115 mph.

• Damage to a corn field shows a narrow path of convergent damage. Likely starting point
• Multiple trees uprooted and large limbs snapped.
• Significant loss of siding. Part of the roof blown off.
• Damage to a roof at a outbuilding at a business.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

The remnants of Hurricane Ida impacted the mid-Atlantic on September 1, 2021. As it moved northward, Ida began transitioning to a strong mid-latitude cyclone with pronounced frontal features, but with continued tropical moisture. On a regional level, the remnants of Ida became one of the most severe natural disasters in US history, due to a combination of several tornadoes, some of them strong, as well as catastrophic flooding over a large and densely populated area. The severe weather threat unfolded as the system's developing warm front lifted northward from the Delmarva region into Pennsylvania and New Jersey. South of the warm front, partial clearing and moderate to strong instability developed. Meanwhile, very strong shear and forcing, along with tropical moisture, were present within the warm sector. The result was widespread convection in the form of both supercell and quasi-linear thunderstorms. A number of storms became severe across the region, producing several tornadoes and other instances of wind damage. This continued an exceptionally active stretch of high end severe weather in the region, coming barely a month after the tornado outbreak of July 29.

An embedded supercell in a quasi-linear feature produced a |tornado near Oxford, PA. A path of damage began in crop land near |the intersection of 5th Street and Waterway Road. Tree damage |continued northeast of here. ||Significant damage occurred in the Wiltshire Development. On Slate|Hill Drive, one house lost a southeast facing exterior wall. |Another house lost a significant amount of siding and a portion |of the roof. Tree damage continued in a northeast path. At Hickory|Hill Road, there was damage to the roof of a commercial |outbuilding and a recreational trailer was flipped on its side.||Sporadic tree and crop damage was noted from drone footage (this |portion of the path was inaccessible by vehicle) continuing to the|northeast. A metal storage building at a business along Reedville|Road had wall and roof damage. Further northeast there was damage|to turkey pens near the intersection of Baltimore Pike and West |Branch Road. Just a little further northeast, there was also heavy damage to a couple of barns, outbuildings, and porch structures on Conner Rd.||Additional tree and power pole damage continued in a northeast |path. The last damage noted along this continuous path was |exterior wall damage to a farm outbuilding and crop damage along |Street Road near Route 10. Sporadic tree damage was observed near |Route 10 and Ewing Road, but this does not appear to be in a |continuous path from the other damage, so this may have been |caused by straight line winds.

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

2 minutes of warning. NWS PHI issued a tornado warning for this county at 20:13 UTC, 2 minutes before the tornado touched down, in force until 20:45 UTC.

The county was under a tornado watch, issued at 16:41 UTC and running to 01:54 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 Enhanced Risk, with a 0.10 chance of a tornado within 25 miles. The outlook in force was issued at 19:46 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.

The Dover AFB radar (KDOX), 118 km away, was scanning. The volume nearest the touchdown began at 20:16 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.

Local storm reports within 60 km of the path, in the three hours either side.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

The live radar over the trackEvery 2021 tornado in PennsylvaniaEvery tornado in Pennsylvania since 1950Warnings in force in Pennsylvania nowThe forecast where you are

10 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.