EF0 tornado, Marston to Andalusia, Illinois, December 23, 2015

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

December 23, 2015

Touchdown

4:33 PM CST (22:33 UTC)

Lifted

4:46 PM CST (22:46 UTC)

On the ground

13 minutes

Path length

10.6 miles (17.1 km)

Path width

50 yards (46 m)

Deaths

0

Injuries

0

Counties

Mercer and Rock Island counties

Touchdown point

41.315, -90.773

Lift-off point

41.444, -90.662

Record number

1512231633-01

5 damage points were recorded along this path by NWS DVN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF0. The highest wind the damage implies is 75 mph.

• 10 inch diameter tree limbs snapped off. No structural damage.
• 6 inch diameter tree limbs snapped. End point of tornado.
• 8 inch diamater tree limbs snapped. No structural damage.
• Tornado crossed IL State Hwy 94 moving north. No visible damage. Eyewitness account.

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

A storm system lifting northeastward during the day on the 23rd brought a warm front into eastern Iowa and northwest Illinois. This allowed unseasonably warm, moist air to flow into northwest Illinois with scattered showers and thunderstorms developing by the late afternoon and early evening. The thunderstorms produced pea sized hail in west central Illinois along with 2 separate tornadoes that traveled from McDonough County into Warren County and another that traveled from Mercer County into Rock Island County. In addition to the thunderstorms, there was also heavy rain and strong gusty gradient winds of 40 to 50 MPH.

An EF-0 tornado with estimated peak winds of 75 mph, began in rural Mercer County Illinois and was on the ground for 1.2 miles before continuing into Rock Island County for another 9.6 miles. The tornado snapped 6 to 10 inch tree branches along its path. There was no structural damage visible along the tornado track.

An EF-0 tornado with estimated peak winds of 75 mph, began in rural Mercer County Illinois and was on the ground for 1.2 miles before continuing into Rock Island County for another 9.4 miles. The tornado snapped 6 to 10 inch tree branches along its path. There was no structural damage visible along the tornado track.

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.

The county was under a tornado watch, issued at 19:58 UTC and running to 23:32 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 19:37 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 Quad Cities radar (KDVN), 28 km away, was scanning. The volume nearest the touchdown began at 22:33 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

30 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.