EF0 tornado, Elburn to Lily Lake, Illinois, August 19, 2009

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 19, 2009

Touchdown

6:15 PM CDT (23:15 UTC)

Lifted

6:16 PM CDT (23:16 UTC)

On the ground

1 minutes

Path length

0.8 miles (1.2 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

County

Kane County

Touchdown point

41.932, -88.470

Lift-off point

41.943, -88.468

Record number

0908191715-01

1 damage points were recorded along this path by NWS LOT, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 105 mph.

• Multiple tree snapped off. Path width of 40 yards.

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

Severe thunderstorms developed during the afternoon hours and moved northeast across parts northern and central Illinois. Three tornadoes were confirmed during this event.

A tornado touched down just north of Route 38. At this location, a field of corn was flattened in a covergent manner towards the northwest. Damage was rated EF0 with winds near 65 mph and a path width of 20 yards. The tornado moved northwest and intensified as it moved along Route 47 where it snapped off and uprooted multiple large hardwood and softwood trees. The damage at this location was blown in a convergent pattern to the northwest. EF1 damage was observed with winds estimated near 105 mph and a path width of 40 yards. The tornado continued to the northwest maintaining its strength causing more tree damage along Route 47. Several trees were snapped off and consistently blown in the same direction to the northwest. Several cars were damaged by falling tree limbs. Damage was rated EF1 at this location with winds near 105 mph and a path width of 40 yards. Several residences along Route 47 continued to receive damage to many trees on their property even as the tornado was weakening. The last of the damage observed was in a corn field just to the west of Route 47. Here corn was flattened and twisted before the the tornado lifted with the damage rated EF0 with winds near 65 mph.

A tornado touched down in a subdivision about a half mile north of Route 64. At this location, several large hardwood tree limbs were snapped and twisted off. Damage here was rated EF0 with winds near 75 mph and a path width of 30 yards. The tornado quickly moved to the northeast where it continued to cause damage to multiple large trees in this subdivision. The tornado began to weaken and produced the last of its damage about a quarter mile north of Route 64 where several large tree limbs were snapped off. Damage was rated EF0 with winds near 70 mph and a path width of 30 yards.

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

18 minutes of warning. NWS LOT issued a tornado warning for this county at 22:57 UTC, 18 minutes before the tornado touched down, in force until 23:30 UTC.

The county was under a tornado watch, issued at 17:49 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 0.05 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.

Chicago/Dupage (DPA), 19 km from the path, in the two hours either side.

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

The Chicago radar (KLOT), 49 km away, was scanning. The volume nearest the touchdown began at 23:15 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.