Tornadoes · United States · Maryland · 2011
EF0 tornado, Garfield, Maryland, May 17, 2011
This EF0 tornado ran 1.1 miles across Frederick County on May 17, 2011, touching down at 5:35 PM EDT and reaching 50 yards wide. It killed nobody, and did $20,000 of property damage.
The rating scale
Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.
EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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.
The record
- Rating
- EF0
- Date
- May 17, 2011
- Touchdown
- 5:35 PM EDT (21:35 UTC)
- Lifted
- 5:39 PM EDT (21:39 UTC)
- On the ground
- 4 minutes
- Path length
- 1.1 miles (1.8 km)
- Path width
- 50 yards (46 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $20,000
- County
- Frederick County
- Touchdown point
- 39.590, -77.539
- Lift-off point
- 39.603, -77.551
- Record number
- 1105171535-01
What the Weather Service recorded
Low pressure both at the surface and aloft developed remained over the Mid-Atlantic during on the 17th. A southeast flow around this system ushered in plenty of moisture off the Atlantic Ocean. The moisture caused moderate amounts of instability to develop. An upper-level disturbance combined with the moderate instability to trigger showers and thunderstorms. Winds changing in speed and direction with height caused an isolated thunderstorm to produce a tornado across north-central Maryland.
Trees were snapped and uprooted along a track that began from south-southeast of the intersection of Forest School Road and Brandenburg Hollow Road to southwest of the intersection of Garfield Road and John Cline Road. Minor shingle damage was noted to two structures. ||Siding was partially removed from a single-family home, where a backyard play center that had been bolted to the ground was snapped from its moorings and rolled.
From NOAA NCEI's Storm Events Database, the narrative the local forecast office wrote for Storm Data.
The warnings
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 forecast that day
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 19:47 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 air that afternoon
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.
Washington/Dulle, VA (KIAD), 12:00Z
9.6 hours before the tornado, 73 km from the path. May 17, 2011.
- Mixed-layer CAPE
- 183 J/kg
- Mixed-layer CIN
- -15 J/kg
- Surface CAPE
- 307 J/kg
- Mixed-layer LCL
- 465 m above ground
- 0-6 km bulk shear
- 18 kt
- 0-1 km bulk shear
- 15 kt
- 0-1 km storm-relative helicity
- 104 m²/s²
- 0-3 km storm-relative helicity
- 139 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
- 0-3 km lapse rate
- 5.9 K/km
Washington/Dulle, VA (KIAD), 00:00Z
2.4 hours after it, 73 km from the path. May 18, 2011.
- Mixed-layer CAPE
- 503 J/kg
- Mixed-layer CIN
- -8 J/kg
- Surface CAPE
- 740 J/kg
- Mixed-layer LCL
- 868 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- 127 m²/s²
- 0-3 km storm-relative helicity
- 159 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.4
- 0-3 km lapse rate
- 7.2 K/km
The surface observations
Camp David (RSP), 9 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 19:54 UTC | 59 | 57 | 140° 7 kt | 15 | 1006.4 | |
| 20:06 UTC | 59 | 55.4 | 140° 8 kt | 18 | 1006.8 | |
| 20:29 UTC | 60.8 | 55.4 | 130° 7 kt | 19 | 1007.1 | |
| 20:54 UTC | 63 | 56 | 140° 10 kt | 18 | 1007.1 | |
| 21:29 UTC | 60.8 | 57.2 | 130° 8 kt | 17 | 1006.8 | -RA |
| 21:56 UTC | 60.8 | 57.2 | 120° 10 kt | 19 | 1007.1 | RA BR |
| 22:05 UTC | 60.8 | 57.2 | 140° 8 kt | 19 | 1007.5 | +RA BR |
| 22:09 UTC | 60.8 | 57.2 | 0° 6 kt | 18 | 1007.1 | -RA BR |
| 22:15 UTC | 60.8 | 59 | 170° 7 kt | 17 | 1007.5 | -RA BR |
| 22:32 UTC | 60.8 | 59 | 120° 9 kt | 18 | 1007.8 | BR |
| 22:43 UTC | 60.8 | 59 | 0° 5 kt | 15 | 1007.8 | BR |
| 22:54 UTC | 60 | 59 | 0° 6 kt | 1007.8 | -RA BR |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Sterling radar (KLWX), 69 km away, was scanning. The volume nearest the touchdown began at 21:34 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.
What was reported nearby
Local storm reports within 60 km of the path, in the three hours either side.
| Time (UTC) | Report | Where | County | Remark |
|---|---|---|---|---|
| 21:34 UTC | TSTM WND DMG | 1 Nne Wolfsville | Frederick, MD | TREES DOWN ALONG BRANDENBURG HOLLOW RD |
| 21:35 UTC | TORNADO | 1 Nne Wolfsville | Frederick, MD | 1.1 MILE EF-0 TORNADO TRACK ASSESSED NEAR WOLFSVILLE. DAMAGE WAS PRIMARILY TO TREES...WITH SIDING DAMAGE NOTED TOWARD THE END OF THE PATH. TORNADO ENDED AT 539 PM. |
| 00:10 UTC | TORNADO | 1 S Maugansville | Washington, MD | 2.1 MILE EF-1 TORNADO TRACK ASSESSED NEAR MAUGANSVILLE. WIDESPREAD TREE DAMAGE WAS OBSERVED ALONG THE PATH. SIDING AND SHINGLE DAMAGE WERE COMMON. ISOLATED STRUCTURAL DAMAGE ALSO NOTED. TORNADO CONTINUED UNTIL JUST AFTER |
| 00:10 UTC | TORNADO | 1 Wsw Maugansville | Washington, MD | LARGE TREES DOWN AND SHINGLES OFF ROOF... TRAINED SPOTTER OBSERVED TORNADO |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2011 tornado in MarylandEvery tornado in Maryland since 1950Warnings in force in Maryland nowThe forecast where you are
The other tornadoes of May 17, 2011
3 more were confirmed in the United States that day.
What this means
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.
Sources
NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.