Tornadoes · United States · Illinois · 2015

EF1 tornado, Andres to Monee, Illinois, September 18, 2015

From Andres to Monee, this EF1 tornado ran 2.6 miles across Will County on September 18, 2015, touching down at 4:44 PM CDT and reaching 50 yards wide. It killed nobody, and did $70,000 of property damage.

The rating scale

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

  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.

The record

Rating
EF1
Date
September 18, 2015
Touchdown
4:44 PM CDT (21:44 UTC)
Lifted
4:53 PM CDT (21:53 UTC)
On the ground
9 minutes
Path length
2.6 miles (4.2 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
Property damage
$70,000
County
Will County
Touchdown point
41.416, -87.860
Lift-off point
41.427, -87.812
Record number
1509181544-01

The damage survey

9 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 90 mph.

  • Approximately 20 trees downed, several uprooted a couple snapped. Trees included Elder, Maple, and Pine

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

What the Weather Service recorded

A low pressure system moved towards northern Illinois during the evening hours, causing thunderstorms to develop in the afternoon and evening hours across northern Illinois and northwest Indiana. A moist environment helped to produce heavy rainfall across portions of northern Illinois. A brief tornado occurred across the Frankfort-Monee area. As the storm moved over northwest Indiana hail and wind damage occurred.

A spotter was located near Green Garden Rd and Harlem and spotted the tornado looking southwest. Damage to a roof and wood swing set was reported at one home. Four to five homes suffered minor roof damage. Six tall trees were snapped and other trees were blown down, including 20 trees at a country club.

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

The warnings

0 minutes of warning. NWS LOT issued a tornado warning for this county at 21:44 UTC, 0 minutes before the tornado touched down, in force until 22:15 UTC.

Issued (UTC)ExpiredProductOffice
21:44 UTC22:15 UTCTornado WarningLOT
22:32 UTC04:30 UTCFlash Flood WarningLOT
00:00 UTC07:21 UTCFlash Flood WatchLOT
04:54 UTC06:00 UTCSevere Thunderstorm WarningLOT

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 Marginal Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 19:59 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.

Lincoln, IL (KILX), 12:00Z

9.7 hours before the tornado, 155 km from the path. September 18, 2015.

Skew-T log-pSkew-T log-p diagram, Lincoln, IL at 12:00Z on 2015-09-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 351 joules per kilogram, CIN -173, lifted condensation level 933 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, Lincoln, IL at 12:00Z on 2015-09-18The 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 218 square meters per square second, 0 to 6 km bulk shear 41 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
351 J/kg
Mixed-layer CIN
-173 J/kg
Surface CAPE
409 J/kg
Mixed-layer LCL
933 m above ground
0-6 km bulk shear
41 kt
0-1 km bulk shear
32 kt
0-1 km storm-relative helicity
218 m²/s²
0-3 km storm-relative helicity
219 m²/s²
Significant tornado parameter
0.1
Supercell composite
4.5
0-3 km lapse rate
4.7 K/km

Open this sounding in Storm Lab

Lincoln, IL (KILX), 00:00Z

2.3 hours after it, 155 km from the path. September 19, 2015.

Skew-T log-pSkew-T log-p diagram, Lincoln, IL at 00:00Z on 2015-09-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 905 joules per kilogram, CIN -82, lifted condensation level 910 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, Lincoln, IL at 00:00Z on 2015-09-19The 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 285 square meters per square second, 0 to 6 km bulk shear 48 knots.193958Sfc1 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
905 J/kg
Mixed-layer CIN
-82 J/kg
Surface CAPE
333 J/kg
Mixed-layer LCL
910 m above ground
0-6 km bulk shear
48 kt
0-1 km bulk shear
36 kt
0-1 km storm-relative helicity
285 m²/s²
0-3 km storm-relative helicity
497 m²/s²
Significant tornado parameter
0.1
Supercell composite
1.2
0-3 km lapse rate
4.5 K/km

Open this sounding in Storm Lab

The radar

The Chicago radar (KLOT), 29 km away, was scanning. The volume nearest the touchdown began at 21:42 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
21:10 UTCHEAVY RAIN 0.884 Nnw Coal CityGrundy, ILRAIN FELL IN 20 MINUTES.
21:50 UTCTORNADO5 S FrankfortWill, IL4-5 HOMES WITH SLIGHT ROOF DAMAGE. SIX TALL TREES SNAPPED AND OTHER TREES DOWN. DAMAGE OVER ABOUT A ONE AND A HALF MILE PATH. VIA WILL COUNTY EMA AND SKYWARN.
21:50 UTCTORNADO5 S FrankfortWill, ILROOF DAMAGE TO HOME AND TO SUBSTANTIAL WOOD SWING SET. NEAR INTERSECTION OF SOUTH 88TH AND WEST MONEE-MANHATTAN ROAD. FROM ZAU AIR TRAFFIC CONTROLLER.
21:50 UTCTORNADO5 S FrankfortWill, ILSPOTTER WAS LOCATED NEAR GREEN GARDEN ROAD AND HARLEM AND SPOTTED THE TORNADO LOOKING SOUTHWEST
21:50 UTCTORNADO5 S FrankfortWill, ILTORNADO SPOTTED FROM INTERSECTION OF GREEN GARDEN ROAD AND HARLEM
22:25 UTCHEAVY RAIN 0.853 Sw Midway AirportCook, IL0.85 INCHES OF RAIN IN 24 MINUTES.
22:56 UTCFLASH FLOOD11 S ChicagoCook, ILELDERLY WOMAN RESCUED FROM STALLED VEHICLE NEAR 92ND AND HOYNE AVENUE BY CHICAGO FIRE DEPARTMENT.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2015 tornado in IllinoisEvery tornado in Illinois since 1950Warnings in force in Illinois nowThe forecast where you are

The other tornadoes of September 18, 2015

3 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
September 187:09 PM CDTEF1Miami, KS9.31001
September 187:57 PM CDTEF1Cass, MO5.2100
September 188:32 PM CDTEF0Cass, MO2.325

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.