Tornadoes · United States · Virginia · 1993

F1 tornado, Loudoun County, Virginia, April 16, 1993

This F1 tornado ran 1.7 miles across Loudoun County on April 16, 1993, touching down at 8:35 PM EDT and reaching 60 yards wide. It killed nobody, and did $50,000 to $500,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  1. F040 to 72 mph

    Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

  2. F173 to 112 mphthis tornado

    Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

  3. F2113 to 157 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. F3158 to 206 mph

    Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

  5. F4207 to 260 mph

    Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

  6. F5261 to 318 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.

The record

Rating
F1
Date
April 16, 1993
Touchdown
8:35 PM EDT (00:35 UTC)
Path length
1.7 miles (2.7 km)
Path width
60 yards (55 m)
Deaths
0
Injuries
0
Property damage
$50,000 to $500,000
County
Loudoun County
Touchdown point
39.100, -77.650
Record number
139

What the Weather Service recorded

A tornado touched down approximately 0.5 mile southwest of Saint Louis in the southern part of Loudoun County, and moved east northeast for about 1.7 miles. The storm knocked down and damaged hundreds of trees. On the Innerhouse Farm, roofs of two barns were blown off, windows were blown out and fences were ripped up.

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

The warnings

5 minutes of warning. NWS LWX issued a tornado warning for this county at 00:30 UTC, 5 minutes before the tornado touched down, in force until 01:00 UTC.

Issued (UTC)ExpiredProductOffice
15:28 UTC17:30 UTCFlash Flood WarningLWX
00:13 UTC01:00 UTCSevere Thunderstorm WarningLWX
00:30 UTC01:00 UTCTornado WarningLWX
01:30 UTC03:30 UTCFlash Flood WarningLWX
01:33 UTC02:15 UTCTornado WarningLWX
03:17 UTC05:15 UTCFlash Flood WarningLWX

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. The outlook in force was issued at 06:10 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), 00:00Z

0.6 hours before the tornado, 27 km from the path. April 17, 1993.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 00:00Z on 1993-04-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 372 joules per kilogram, CIN -3, lifted condensation level 626 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Washington/Dulle, VA at 00:00Z on 1993-04-17The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 97 square meters per square second, 0 to 6 km bulk shear 64 knots.1939587897117Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
372 J/kg
Mixed-layer CIN
-3 J/kg
Surface CAPE
869 J/kg
Mixed-layer LCL
626 m above ground
0-6 km bulk shear
64 kt
0-1 km bulk shear
16 kt
0-1 km storm-relative helicity
97 m²/s²
0-3 km storm-relative helicity
-6 m²/s²
Significant tornado parameter
0.2
Supercell composite
1.9
0-3 km lapse rate
6.8 K/km

Open this sounding in Storm Lab

Washington/Dulle, VA (KIAD), 12:00Z

11.4 hours after it, 27 km from the path. April 17, 1993.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 12:00Z on 1993-04-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -17680, lifted condensation level 1070 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 1993-04-17The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity -116 square meters per square second, 0 to 6 km bulk shear 52 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-17680 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1070 m above ground
0-6 km bulk shear
52 kt
0-1 km bulk shear
19 kt
0-1 km storm-relative helicity
-116 m²/s²
0-3 km storm-relative helicity
90 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.6 K/km

Open this sounding in Storm Lab

The surface observations

Washington/Dulles (IAD), 25 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
22:37 UTC150° 10 kt1002
23:00 UTC6661160° 8 kt1001.7
00:00 UTC6461150° 8 kt1001.7
00:06 UTC160° 10 kt1001.7
00:24 UTC150° 10 kt1001.7TS
01:00 UTC6361140° 7 kt1002TSRA
02:00 UTC6361160° 10 kt1002TSRA
02:24 UTC170° 12 kt1002.7TS

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

The radar

The Sterling radar (KLWX), 20 km away, was scanning. The volume nearest the touchdown began at 00:37 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.

This ground now

The live radar over the trackEvery 1993 tornado in VirginiaEvery tornado in Virginia since 1950Warnings in force in Virginia nowThe forecast where you are

The other tornadoes of April 16, 1993

8 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
April 168:30 AM EDTF1Fauquier, VA1.280$50,000 to $500,000
April 169:00 AM EDTF0Vance, NC0.210$50,000 to $500,000
April 163:00 PM EDTF1Queen Anne's, MD0.533$5,000 to $50,000
April 163:20 PM EDTF1Luzerne, PA2.1400$50,000 to $500,000
April 168:25 PM EDTF0Loudoun, VA0.730$500 to $5,000
April 168:45 PM EDTF0Snyder, PA0.230$5,000 to $50,000
April 169:00 PM EDTF0Fauquier, VA0.850$500 to $5,000
April 169:40 PM EDTF1Northumberland, PA0.230$5,000 to $50,000

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.