EF1 tornado, Milford Arpt to Slaughter Beach, Delaware, July 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 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 1, 2021

Touchdown

5:00 PM EDT (21:00 UTC)

Lifted

5:07 PM EDT (21:07 UTC)

On the ground

7 minutes

Path length

4.7 miles (7.6 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Sussex County

Touchdown point

38.921, -75.390

Lift-off point

38.912, -75.303

Record number

2107011500-01

After a significant heatwave, a cold front approached the mid-Atlantic on July 1, 2021. A potent mid-level trough was also digging southward through southern Ontario and into the Great Lakes region, and a strong upper level jet streak was present downstream the trough axis, over the interior mid-Atlantic and northern New England. This strong upper level forcing combined with the approaching front and a lingering warm, moist air mass ahead of it caused widespread thunderstorm development on July 1. Storms occurred almost exclusively south of Interstate 78, in the environment of best instability. A number of storms became severe, taking the form of mainly linear and multi-cellular clusters but with some embedded supercellular characteristics. Straight line wind damage was the primary hazard, with a number of reports of downed trees and power outages due to winds. In addition, two confirmed EF-1 tornadoes occurred over southern Delaware. A remnant outflow boundary from earlier storms to the north, combined with sea/bay breezes in the area, likely caused a localized enhancement of low level wind shear and created a corridor of enhanced tornado potential. With the cold front remaining to the west, some storm activity continued into the overnight, but storm coverage and intensity gradually waned with the loss of daytime heating and the overturning of the atmosphere from earlier storms.

Damage was first observed near residences at the Cedar Beach Road|and McColley Road intersection. Here, several large branches and |trees were snapped. Further east along Cedar Beach Road, more tree|damage occurred across several residences with a couple of trees |having been uprooted. The tornado then uplifted part of a porch |roof to a residence on Shockley Road. Insulation that was |underneath the roof was blown across Shockley Road and adhered to |nearby homes. Insulation was also noted on all sides of the |affected residence. At the intersection of Shockley and Cedar Neck|Roads, a residence also had a large television antenna that was |bent 180 degrees down towards the ground. Further east on Mills |road, another residence observed multiple trees that were snapped.|One large branch fell on an outdoor shed causing it to collapse, |with other large branches falling on vehicles causing window |damage. Towards Fannies Way, additional EF-1 damage was noted with|a majority of roofing material lost to a pole barn along with two|enclosed trailers being overturned. Roofing material from the |pole barn along with tree branches were observed in the adjacent |corn field. The tornado then moved eastward into marshland and |proceeded towards the intersection of Bay Avenue and Slaughter |Beach Road. Another pole barn lost a majority of roofing at the |intersection with a small trailer having been overturned. Smaller |tree branches were then snapped as the tornado lifted near the |Delaware coastline. Interestingly, a nearby DEOS mesonet site |measured a peak wind gust of 62 mph near this endpoint.

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

3 minutes of warning. NWS PHI issued a tornado warning for this county at 20:57 UTC, 3 minutes before the tornado touched down, in force until 21:19 UTC.

The county was under a severe thunderstorm watch, issued at 16:48 UTC and running to 22:52 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. The outlook in force was issued at 19:49 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), 13 km away, was scanning. The volume nearest the touchdown began at 21:02 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 DelawareEvery tornado in Delaware since 1950Warnings in force in Delaware nowThe forecast where you are

3 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.