EF1 tornado, Round Lake to Gages Lake, Illinois, August 2, 2015

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 mphthis tornado

   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

EF1

Date

August 2, 2015

Touchdown

8:38 PM CDT (01:38 UTC)

Lifted

8:53 PM CDT (01:53 UTC)

On the ground

15 minutes

Path length

7.5 miles (12.1 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

Property damage

$1.0 million

County

Lake County

Touchdown point

42.350, -88.097

Lift-off point

42.343, -87.951

Record number

1508021938-01

4 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 100 mph.

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

An isolated supercell thunderstorm developed over north central Illinois and moved across portions of the Chicago metropolitan area during the afternoon of August 2nd, producing large hail and severe winds. A 35 year old man was killed at an outdoor event in Wood Dale when a large tent collapsed causing a beam to strike the man. Another 20 people were injured, including three seriously injured. One of the seriously injured, an 81 year old woman died from her injuries in January 2016. Additional thunderstorms formed later in the evening producing severe weather, including a tornado near Grayslake.

The tornado touched down near Cedar Lake Road in Round Lake where tree damage occurred. The tornado moved east and damaged hundreds of trees along the 7.5 mile long path, including dozens that were snapped at the base or uprooted. The most significant tree damage was noted in the subdivisions of Grayslake and Wildwood. A roof was blown off of a restaurant along Illinois Route 134 with a sign from the restaurant ending up over two miles away in Grayslake. Several homes and businesses suffered roof damage from either falling trees or loss of shingles. A large part of the roof of the Grayslake Central High School was blown across the street. A nearby skatepark was heavily damaged. The last points of damage were noted along Illinois Route 120 just west of I-94 in unincorporated Wildwood.

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. One was issued for the county at another hour that day.

The county was under a severe thunderstorm watch, issued at 01:31 UTC and running to 03:51 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 Enhanced Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 01:07 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.

Waukegan (UGN), 16 km from the path, in the two hours either side.

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

The Milwaukee radar (KMKX), 81 km away, was scanning. The volume nearest the touchdown began at 01:38 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 2015 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

4 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.