Tornadoes · United States · Kansas · 2018

EF0 tornado, Horace, Kansas, August 18, 2018

This EF0 tornado ran 0.3 miles across Greeley County on August 18, 2018, touching down at 4:40 PM MDT and reaching 25 yards wide. It killed nobody.

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 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.

The record

Rating
EF0
Date
August 18, 2018
Touchdown
4:40 PM MDT (22:40 UTC)
Lifted
4:41 PM MDT (22:41 UTC)
On the ground
1 minutes
Path length
0.3 miles (0.5 km)
Path width
25 yards (23 m)
Deaths
0
Injuries
0
County
Greeley County
Touchdown point
38.587, -101.857
Lift-off point
38.583, -101.857
Record number
1808181640-01

What the Weather Service recorded

Scattered thunderstorms developed along a surface boundary near the Colorado/Kansas border during the latter half of the afternoon. One of the thunderstorms produced a brief tornado in northern Greeley County, blew a tree over in Tribune with estimated wind speeds of 100 MPH, and produced golf ball size hail south of Tribune.

No damage was reported with this tornado. According to reports, the tornado occurred near the CR I/CR 11 intersection.

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

The warnings

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.

Issued (UTC)ExpiredProductOffice
22:01 UTC22:45 UTCSevere Thunderstorm WarningGLD
22:43 UTC23:30 UTCSevere Thunderstorm WarningGLD
23:12 UTC23:45 UTCTornado WarningGLD
23:24 UTC00:15 UTCSevere Thunderstorm WarningGLD
23:42 UTC00:15 UTCTornado WarningGLD
00:00 UTC03:00 UTCFlash Flood WarningGLD

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 Slight Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 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.

Denver, CO (KDEN), 12:00Z

10.7 hours before the tornado, 185 km from the path. August 18, 2018.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2018-08-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 412 joules per kilogram, CIN -229, lifted condensation level 1881 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, Denver, CO at 12:00Z on 2018-08-18The 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 -8 square meters per square second, 0 to 6 km bulk shear 7 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
412 J/kg
Mixed-layer CIN
-229 J/kg
Surface CAPE
210 J/kg
Mixed-layer LCL
1881 m above ground
0-6 km bulk shear
7 kt
0-1 km bulk shear
3 kt
0-1 km storm-relative helicity
-8 m²/s²
0-3 km storm-relative helicity
13 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.8 K/km

Open this sounding in Storm Lab

Denver, CO (KDEN), 00:00Z

1.3 hours after it, 185 km from the path. August 19, 2018.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2018-08-19Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 183 joules per kilogram, CIN -88, lifted condensation level 1957 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, Denver, CO at 00:00Z on 2018-08-19The 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 -13 square meters per square second, 0 to 6 km bulk shear 36 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
183 J/kg
Mixed-layer CIN
-88 J/kg
Surface CAPE
824 J/kg
Mixed-layer LCL
1957 m above ground
0-6 km bulk shear
36 kt
0-1 km bulk shear
12 kt
0-1 km storm-relative helicity
-13 m²/s²
0-3 km storm-relative helicity
70 m²/s²
Significant tornado parameter
-0.0
Supercell composite
-0.2
0-3 km lapse rate
8.7 K/km

Open this sounding in Storm Lab

The surface observations

Syracuse (3K3), 67 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:55 UTC87.864.4150° 14 kt191015.9
21:15 UTC87.864.4130° 13 kt221015.2
21:35 UTC87.864.4170° 12 kt161014.9
21:55 UTC84.262.6150° 15 kt201014.2
22:15 UTC82.464.4140° 12 kt1014.2
22:35 UTC82.464.4130° 13 kt201013.9
22:55 UTC80.664.4120° 13 kt1013.9
23:15 UTC78.862.680° 19 kt241013.9
23:35 UTC73.462.680° 19 kt231013.5
23:55 UTC6864.450° 12 kt211014.2-RA
00:15 UTC66.264.4330° 6 kt211015.9RA
00:35 UTC64.464.420° 23 kt301015.9

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

The radar

The Goodland radar (KGLD), 88 km away, was scanning. The volume nearest the touchdown began at 22:40 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
22:17 UTCHAIL 113 Ssw Sharon SpringsWallace, KSNICKEL TO QUARTER SIZE HAIL FELL.
22:40 UTCTORNADO9 Nnw HoraceGreeley, KSREPORT OF A TORNADO TOUCHING DOWN BRIEFLY.
23:20 UTCTSTM WND GST 681 Wnw HoraceGreeley, KS
23:30 UTCTSTM WND GST 50TribuneGreeley, KSREPORT OF TREE LIMBS ON THE GROUND.
23:30 UTCTSTM WND GST 80TribuneGreeley, KSCORRECTS PREVIOUS TSTM WND GST REPORT FROM TRIBUNE. CORRECTS PREVIOUS TSTM WND GST REPORT FROM TRIBUNE. REPORT OF TREE BLOWN DOWN.
23:30 UTCTSTM WND GST 80TribuneGreeley, KSCORRECTS PREVIOUS TSTM WND GST REPORT FROM TRIBUNE. REPORT OF TREE BLOWN DOWN.
23:30 UTCTSTM WND GST 580TribuneGreeley, KSCORRECTS PREVIOUS TSTM WND GST REPORT FROM TRIBUNE. REPORT OF TREE BLOWN DOWN.
23:30 UTCHAIL 1TribuneGreeley, KS
23:50 UTCTSTM WND GST 585 S TribuneGreeley, KS
23:50 UTCHAIL 1.755 S TribuneGreeley, KSHOUSE WINDOWS DAMAGED.

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

This ground now

The live radar over the trackEvery 2018 tornado in KansasEvery tornado in Kansas since 1950Warnings in force in Kansas nowThe forecast where you are

The other tornadoes of August 18, 2018

1 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 182:22 PM MSTEF0Coconino, AZ3.110

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.