EF3 tornado, Williamsville to Beason, Illinois, August 19, 2009

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 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 mphthis tornado

   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

EF3

Date

August 19, 2009

Touchdown

3:19 PM CDT (20:19 UTC)

Lifted

4:02 PM CDT (21:02 UTC)

On the ground

43 minutes

Path length

24.3 miles (39.1 km)

Path width

880 yards (805 m)

Deaths

0

Injuries

19

Property damage

$18 million

Crop damage

$1,075,000

Counties

Sangamon and Logan counties

Touchdown point

39.956, -89.561

Lift-off point

40.147, -89.166

Record number

0908191419-01

57 damage points were recorded along this path by NWS ILX, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF3. The highest wind the damage implies is 145 mph.

• Wide swath of corn field flatted. See evidence of strong inflow.
• two grain buildings, gone. back into flat corn field... track back up to house where it busted up the tree line. and an outbuilding...
• Center of tornado track crossing road
• Southern edge of path. Corn field flattened.

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

A vigorous upper-level disturbance in conjunction with a warm front lifting northward through central Illinois triggered strong to severe thunderstorms during the afternoon and evening of August 19th. Embedded supercells within a long line of storms produced enhanced wind damage and tornadoes. Seven tornadoes touched down on August 19th, affecting parts of Scott, Morgan, Sangamon, Logan, DeWitt, McLean, and Vermilion counties. The strongest tornado was rated as an EF3 by an NWS Storm Survey as it tracked across southern Logan County. Total damages to crops and property from the 7 tornadoes were estimated to be more than $25 Million.

The tornado touched down on the west side of Williamsville, just west of I-55, at 319 PM CST. It destroyed an antique mall, damaged the Casey's gas station building and collapsed the canopy over the gas pumps. One person was injured at the mall, while 2 motorcyclists were injured when they were thrown from their bikes. The tornado moved northeast through Williamsville and hit a church, throwing a 2-horse trailer onto the roof and collapsing the roof over half of the building. One person inside the church was injured. The tornado continued through the northern portion of town, causing damage to numerous trees and several homes. Two homes lost their roof and several others lost a portion of their roof. The tornado also caved in the southern end of a metal building, part of an agricultural business on the edge of town. A total of 12 additional people were injured by tornado debris in the town of Williamsville. The width of the tornado through town ranged from 100 to 150 yards. The maximum wind speed of 135 mph (EF2) in Williamsville was determined from the damage to the church. A total of 10 houses were destroyed and 35 houses damaged in Williamsville. A total of six businesses and non-residential properties were destroyed.||The tornado continued east-northeast and flattened cornfields, damaged farm outbuildings and machine sheds, and damaged homes, garages, and vehicles on Lester Rd. Two houses were completely destroyed, and four others had extensive damage, as the tornado widened to 600 yards at this point. A 19-month-old baby was injured as the family home was hit by the tornado. ||The maximum wind speed at this point was estimated at 140 mph (EF3). The tornado continued through fields, causing extensive crop damage, until crossing into Logan County around 326 PM CST. Path length through Sangamon County was 4.5 miles.

The tornado moved into Logan county from Sangamon county at 326 PM CST and continued heading northeast. It widened to 1/2 mile at several locations along its path. The tornado destroyed 7 houses and damaged 15 others. Numerous grain bins and outbuildings were also destroyed. Crop losses were extensive along the 20 mile path and were estimated to be around $1 Million. Two people sustained injuries when the shed they were seeking shelter in was destroyed.||Wind speeds were estimated at 140 mph as the tornado crossed from Sangamon County, decreasing to 110 to 120 mph as it moved to areas between Lincoln and Mt. Pulaski. The tornado continued northeast before weakening to speeds of 90 to 100 mph, with a width of 50 to 100 yards. The tornado dissipated just east of Beason at 402 PM CST. The path length in Logan County was nearly 20 miles.

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

29 minutes of warning. NWS ILX issued a tornado warning for this county at 19:50 UTC, 29 minutes before the tornado touched down, in force until 20:30 UTC.

The county was under a tornado watch, issued at 17:51 UTC and running to 00:00 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, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 21:34 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.

Lincoln (AAA), 12 km from the path, in the two hours either side.

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

The Lincoln radar (KILX), 11 km away, was scanning. The volume nearest the touchdown began at 20:18 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 2009 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

29 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.