EF1 tornado, Stines Corner to Slatington, Pennsylvania, July 29, 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 mphthis tornado

   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

EF1

Date

July 29, 2021

Touchdown

4:25 PM EDT (20:25 UTC)

Lifted

4:29 PM EDT (20:29 UTC)

On the ground

4 minutes

Path length

1.1 miles (1.9 km)

Path width

75 yards (69 m)

Deaths

0

Injuries

0

County

Lehigh County

Touchdown point

40.758, -75.624

Lift-off point

40.765, -75.604

Record number

2107291425-01

6 damage points were recorded along this path by NWS PHI, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 100 mph.

• Bleachers tossed, roofing removed from a dugout.
• Weakened hardwood tree was also snapped. One softwood snapped but it was only one.
• Airplane hangar with doors blown out.
• Considerable tree damage...including some trees uprooted along a path near Welshtown Rd and Skeet Club Ln

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

A strong shortwave trough moved east-southeastward out of the Great Lakes region on July 29. An associated, strengthening surface low also tracked out of the Great Lakes and into upstate New York. A warm front associated with this low moved through most of New Jersey and eastern Pennsylvania during the late morning and early afternoon hours. This front, combined with the remains of widespread convection to the west from the previous overnight and morning hours, brought significant cloud cover to the eastern mid-Atlantic for much of the day on the 29th. This was mainly in the form of mid and high level cloud cover, however, and temperatures still warmed to near seasonal levels behind the warm front, allowing moderate to strong instability to build. Meanwhile, the robust surface and upper level disturbances approaching the region brought both strong forcing and unseasonably strong wind shear. By mid-afternoon, an unusually favorable convective environment existed over eastern Pennsylvania and New Jersey.||The result of this environment was a rare tornado outbreak across the area. Initially, during the mid-afternoon hours, mixed convective modes over east-central Pennsylvania produced a couple instances of damaging wind and brief tornadoes as storms attempted to overcome cloud cover and some light stratiform rain in the area. With time, as storms moved into better instability and a less contaminated environment over far eastern Pennsylvania and New Jersey, they took on more supercellular structures. Multiple cyclic supercells would go on to produce several tornadoes, three of them strong (EF2+) over eastern Pennsylvania and New Jersey. Convection persisted past the sunset hour with little to no loss in intensity due to the strong forcing. The only thing that put an end to the outbreak was the coastline, as storms moved offshore towards 9 to 10PM local time. Even offshore, one supercell continued to exhibit strong rotation and likely produced a strong waterspout for tens of miles over the Atlantic.||Fortunately, and miraculously, no serious injuries or loss of life occurred as a result of this outbreak. With the passage of a cold front late on the evening of the 29th, cooler, drier, and much less active weather would grace the region for several days as clean-up efforts began.

The tornado which began in western Albany Twp, Berks County, continued into Lehigh County. It tracked between between Kunkels Mill Rd and Red Rd near the far |southern tip of Lynn Twp. Mostly minor crop and |tree damage was observed in this area, but with a continued clear |convergent pattern. A resident on Red Rd filmed the tornado as it |passed to his south. The tornado passed through an open field before |crossing Rhoads Rd, where tree and minor roofing damage were |sustained. East of Rhoads Rd, a number of trees were snapped and |uprooted as the tornado approached New Smithville Rd. The tornado |crossed Golden Key Rd, uprooting a few more trees, before |dissipating in a field prior to reaching Loch Valley Rd in |Weisenberg Twp. The extent of tree damage both near the start of the |path in Berks County and in the New Smithville Rd area merited an EF1 |rating.

This tornado initially caused considerable tree damage on |Welshtown Road and Skeet Club Lane including mutliple uprooted |hardwood trees. It continued on the grounds of Northern Lehigh |High School in Slatington. Several trees were snapped or uprooted |at the atletic fields of the high school, with most of the |snapping occurring high up in the trees. A wooden dugout on the |school's baseball field lost its roof, and some unanchored metal |bleachers were tossed. Damage was mostly blown in a similar west |to east direction, but there was some evidence of convergence |especially in tree damage in the area. In a neighborhood east of |the high school, a tree was snapped about one third of the way up |the trunk. At the Slatington Airport, an airplane hangar door was |blown out and there was tree damage on the airport property. |Damage became more unidirectional near the airport as the |circulation likely gusted out. Little if any damage occurred east |of the airport property, and that is where the tornado path is |estimated to have ended.

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

22 minutes of warning. NWS PHI issued a tornado warning for this county at 20:03 UTC, 22 minutes before the tornado touched down, in force until 20:30 UTC.

The county was under a tornado watch, issued at 18:25 UTC and running to 00:52 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 0.02 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.

Lehighton (22N), 14 km from the path, in the two hours either side.

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

The Philadelphia radar (KDIX), 136 km away, was scanning. The volume nearest the touchdown began at 20:26 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.