EF0 tornado, Coster, Maryland, August 4, 2020

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

August 4, 2020

Touchdown

6:52 AM EDT (10:52 UTC)

Lifted

6:53 AM EDT (10:53 UTC)

On the ground

1 minutes

Path length

0.8 miles (1.3 km)

Path width

175 yards (160 m)

Deaths

0

Injuries

0

Property damage

$250,000

County

Calvert County

Touchdown point

38.334, -76.478

Lift-off point

38.343, -76.470

Record number

2008040452-01

27 damage points were recorded along this path by NWS LWX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 95 mph.

• Several trees snapped and uprooted.
• Several trees snapped and uprooted along Medleys Neck Road.
• Several trees snapped and uprooted along Blake Creek Road.
• Several trees snapped and uprooted along Richey Rd and Dry Creek Lane.

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

Tropical Storm Isaias moved up the east coast, passing through southern Maryland on the morning of Tuesday, August 4th, 2020, spawning several tornadoes as well as flooding rain and tropical storm force winds. ||Storm total rainfall ranged from 2 to 4 inches near Interstate 95 to as much as 9 inches in Calvert County east of Interstate 95. The heavy rain led to numerous incidents of flooding and flash flooding, especially near and east of Interstate 95. ||The highest sustained wind of 46 knots was reported at Bishops Head and the highest peak gust of 63 knots was also reported at Bishops Head. ||There were three tornadoes associated with Isaias over southern Maryland and there were also numerous reports of downed trees from tropical storm force winds, especially near and east of Interstate 95. ||A storm surge of 1 to 2 feet occurred along the western shore of the Chesapeake Bay and the shore of the Tidal Potomac River. This did result in minor tidal Flooding in Washington DC.

One of four confirmed tornadoes spawned by Tropical Storm Isaias|over lower southern Maryland touched down along Point Patience Drive|between the Navy Recreation Center Solomons Fishing Pier and Third|Cove. The tornado tracked northeastward roughly along Patuxent|Drive, uprooting and snapping numerous trees along its path. The|trees fell in a convergent manner over a path of nearly one mile|long and about 175 yards wide, indicating a tornadic circulation was|in contact with the ground. Two recreational vehicles on the Navy|facility were smashed by falling trees. Fortunately there were no|occupants at the time. Trees fell on numerous recreational|facilities on the compound, and damage was noted to outdoor|umbrellas at the pool which were rated for hurricane force winds.|NWS 88D Doppler Radar, as well as the FAA Terminal Doppler Weather Radars|TDCA and TADW all indicated strong rotation over this area.||The tornadic damage ended near the north end of the Naval facility,|and no damage was noted in the adjacent residential community to the|north. Many other scattered trees were knocked down all across|Calvert County and lower southern Maryland due to winds associated|with Tropical Storm Isaias.

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

8 minutes of warning. NWS LWX issued a tornado warning for this county at 10:44 UTC, 8 minutes before the tornado touched down, in force until 11:15 UTC.

The county was under a tornado watch, issued at 06:26 UTC and running to 15:03 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 Marginal Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 05:53 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.

The Dover AFB radar (KDOX), 105 km away, was scanning. The volume nearest the touchdown began at 10:49 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 2020 tornado in MarylandEvery tornado in Maryland since 1950Warnings in force in Maryland nowThe forecast where you are

30 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.