F1 tornado, Boonsboro, Maryland, August 26, 1999

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.

Rating

F1

Date

August 26, 1999

Touchdown

3:38 PM EDT (19:38 UTC)

Path length

1.5 miles (2.4 km)

Path width

60 yards (55 m)

Deaths

0

Injuries

0

Property damage

$70,000

County

Washington County

Touchdown point

39.470, -77.650

Lift-off point

39.470, -77.650

Record number

631

A line of intense thunderstorms moved across much of Maryland during the afternoon, producing damaging winds and frequent lightning. Storm winds weakened and the speed of the line slowed as it moved south and east of Frederick and Carroll Counties. The resulting line of showers that moved into Prince Georges, Anne Arundel, and Baltimore Counties produced copious amounts of rainfall and led to flash flooding. South of Hagerstown in Washington County, winds in excess of 55 MPH downed several trees. Eight trees were downed onto Spielman Road, blocking the street for 90 minutes. Power lines were downed onto Sharpsburg Pike and Tilghmanton Road. A one mile wide and two mile long area just south of Boonsboro bore the brunt of concentrated downburst winds between 60 and 70 MPH. Numerous trees were snapped and uprooted, a satellite dish was damaged, a tree fell onto a home causing minor damage, and tin roof sheets were torn from a barn, resulting in $5000 in losses. Up to 100 customers lost power as a direct result of the storm, including residents of Sharpsburg and Keedysville. A gustnado, or squall line tornado, formed just north of the this path of concentrated damage, about 2 miles south of Boonsboro. The gustnado had a damage path which was 1.5 miles long and 60 yards wide, produced $75,000 in damage, and was of F1 strength. Most of the damage from the gustnado was concentrated in the Route 67, Appleton road, and Netz Road area, knocking out power to 500 residents. The twister passed across a dairy farm along Appleton Road and ripped a third of the roof off a milking barn, stripped siding and trim from farm buildings, and carried 8 calf igloos and other debris up to one quarter mile away. Some of the the beams from the milking barn roof were driven up to 2 feet into the ground after coming to rest on the next farm. An estimated $5000 damage was done to the farm. Farther down Appleton Road, the gustnado inflicted minor damage to a barn, a garage, and a home. Two pine trees were uprooted nearby. Along Netz Road, two homes lost shutters and another had damage to a storm door. Trees were snapped or uprooted, and a trampoline standing up sideways was wrapped around a tree. The gustnado also peeled back the metal roof of a Dogstreet Road house, allowing rain water to damage furniture and electronics. Next, the line of thunderstorms moved into southwest Frederick County. Trees were downed in the Wolfsville and Middletown area. Heavy downpours flooded low lying roads and farmland throughout the county. Heavy downpours were a contributing factor in several accidents in Frederick County. Two accidents occurred on Braddock Mountain at Interstate 70, three accidents occurred on Route 340, and one accident was reported on both Highway 17 and 85. The storm moved into Carroll County and downed several trees and power lines, sending 8000 residents into the dark. In the Westminster area, tree debris and telephone lines covered northbound Highway 97, closing it for 2 hours. Cows got loose along the road after a fence was damaged, forcing county police to stage a roundup. Over two inches of rain fell in Westminster in one hour. Trees and power lines were also downed on Highway 97 near Union Mills. The Union Mills Homestead was damaged after two red maple trees dating back to the Civil War fell onto the miller's house. Maple and apple trees surrounding the property were split or uprooted. Downed trees and power lines blocked Saw Mill Road for several hours. Finksburg reported 2.7 inches of rain and 50 MPH winds. Winds gusted to 86 MPH near Millers at 5:10 PM EDT.Winds diminished as the storms moved into Montgomery, Howard, and Baltimore Counties. The storms also slowed down and started to drop copious amounts of rainfall. Major flooding occurred because the area was still recovering from heavy rains that fell over the region the night before. Montgomery County reported street flooding in Poolesville and Gaithersburg. Over 10,000 customers lost power in Howard County. Elkridge received 2.81 inches of rain and Columbia received 1.55 inches. A total of 1.60 inches fell at Hipsley Mill, about 2 inches fell in Bowie, 2.35 inches fell at Laurel, and up to 4.5 inches fell southeast of Highway 301 in Prince Georges County. Over 5 inches accumulated near Upper Marlboro, causing flooding in low lying areas. Southern Baltimore County and the city of Baltimore reported major flash flooding and Anne Arundel County reported significant flooding after 2 to 7 inches of rain fell in less than 4 hours. Rainfall reports included 3.85 inches in Arnold, 2.24 inches in Davidsonville, 1.63 inches in Rivera Beach, 1.75 inches in Upperco, 7 inches in Woodlawn, 5 inches in Annapolis, and 4.77 inches in downtown Baltimore. Between 6:30 PM and 8:30 PM EDT, 4.6 inches of rain fell at Fort McHenry.In Southern Baltimore County, streets and streams flooded in Owings Mills and Randallstown. Several motorists had to be rescued from quickly rising water. The deluge of rain closed the Maryland State Fair at Timonium on its first night of business. In Woodlawn, a storm drain and culvert near Dead Run Creek swelled with water and overflowed into the parking lot of a car dealership on Security Boulevard. In less than 9 minutes, four feet of water poured onto 70 trucks, totalling 30 cars and resulting in $30 million in damages. Dried mud and twigs were found inside the automobiles after the water subsided. Flooding closed sections of Interstate 83 in Baltimore County and in the city of Baltimore. Water poured off Interstate 83 and quickly reached a depth of 6 feet in a health club parking lot off Clipper Mill Road. Forty cars in the parking lot were damaged, and most of the cars were moved several yards by the force of the water. In Arbutus, occupants of 4 cars at the intersection of Leeds Avenue and Maiden Choice Lane had to be rescued after 4 feet of water poured into the street. Eight people were rescued at the intersection of Security Boulevard and Gwynn Oak Avenue around 7:00 PM EDT after cars became stalled in rapidly moving flood waters. Boston and Aliceanna Streets in Canton and Clipper Mill Road in Woodbury were also impassable. Several flights were delayed or cancelled at Baltimore Washington International Airport (BWI). The city of Baltimore reported numerous roads under water and several stalled vehicles and water rescues. So many streets flooded that officials asked drivers to stay put until the water receded. Over 17,000 residents of the city lost power as a direct result of the storm, and hundreds of basements flooded. Hardest hit were areas near Jones Falls along Interstate 83. An apartment complex next to Jones Falls was inundated with water and cars in the parking lot were floating. The Northwest Ice Rink was inundated with water, and motorists near Camden yards waited on the roofs of their cars to be rescued from waist-high water. A building collapsed around 9:00 PM EDT on Wicomico Street, and rushing water blasted a hole in another home. Rain and mud on railroad tracks and water in the Howard Street tunnel two miles south of Baltimore's Penn Station delayed MARC and Amtrack commuter trains between Washington and Baltimore. It rained so hard that medevac helicopters from the Shock Trauma Center at University Hospital had to be grounded. In Anne Arundel County, Brock Bridge, Mill Creek, Race, River, Rideout, and Severn Side Roads were closed by high water. Part of the Baltimore-Washington Parkway was also closed. During the height of the storm, 1600 county residents lost power. Homes on Potomac Road in Edgewater had knee-deep water flowing inside which ruined furniture on the first floor and flooded basements and garages. High water closed a part of Route 450 between South Haven Road and Eagle Boulevard, Mayo and Washington Road, and several roads in the London Towne area. Heavy rains also caused a failure of erosion control measures at an Annapolis construction site on Gibralter Avenue, sending muddy water streaming down city streets toward Weems Creek. Four inches of rain fell in Annapolis in only 90 minutes.

Damage to farm buildings and equipment, three homes, several trees snapped or uprooted

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

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 Storm Prediction Center had this point in a General Thunderstorms Risk. The outlook in force was issued at 16:13 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 live radar over the trackEvery 1999 tornado in MarylandEvery tornado in Maryland since 1950Warnings in force in Maryland nowThe forecast where you are

2 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.