EF0 tornado, Thornburgh, Pennsylvania, July 29, 2021

1. EF065 to 85 mphthis tornado

   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 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. 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

EF0

Date

July 29, 2021

Touchdown

12:55 PM EDT (16:55 UTC)

Lifted

12:56 PM EDT (16:56 UTC)

On the ground

1 minutes

Path length

0.3 miles (0.4 km)

Path width

15 yards (14 m)

Deaths

0

Injuries

0

Property damage

$15,000

County

Venango County

Touchdown point

41.499, -79.795

Lift-off point

41.500, -79.790

Record number

2107291055-01

9 damage points were recorded along this path by NWS CLE and NWS PBZ, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 85 mph.

• Start point of tornado in field, confirmed by drone footage of flattered cornfield
• Detached garage blown down
• Tree branches broke. 10 yards wide.
• Shallow rooted tree uprooted.

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

A shortwave passage during the morning of July 29th spread mainly non-severe showers and thunderstorms across the region during the morning and midday hours. However, a discrete cell along the back edge of the morning activity was able to develop an EF1 tornado along the Fayette-Westmoreland County border. This was a preview of what was to follow. ||In the wake of this morning activity, instability was able to build as partial clearing occurred. Additional thunderstorms were able to develop in association with a prefrontal trough. These storms were able to take advantage of deep shear, especially in the lower levels. A cross-boundary component to this shear allowed discrete supercells to form during the mid and late afternoon hours. Storm motions were favorable for the ingestion of streamwise vorticity, allowing for rotating storms, and the development of additional tornadoes in southwest Pennsylvania and eastern Ohio. Three additional tornadoes occurred in southwest Pennsylvania, causing generally tree and light structural damage. Thankfully, no injuries were reported. A few other damaging wind reports were received as well.

An EF-0 tornado, that was partially observed by a personal home |surveillance camera and confirmed via damage survey, formed near |Billingsley Road and advanced into an open field before crossing |State Route 417 (near Speer's Public Golf Course) and quickly |dissipating. The tornado passed near a home, snapped about a |dozen pine trees, and then uprooted a shallow rooted hardwood |tree before dissipating. Maximum wind speed was estimated at 85 MPH.

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 Slight Risk. The outlook in force was issued at 16:19 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.

Franklin(Awos) (FKL), 15 km from the path, in the two hours either side.

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

The Pittsburgh radar (KPBZ), 113 km away, was scanning. The volume nearest the touchdown began at 16:53 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

36 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.