Tornadoes · United States · Colorado · 2024
Unrated tornado, Shamrock, Colorado, August 19, 2024
This Unrated tornado ran 0.6 miles across Adams County on August 19, 2024, touching down at 2:04 PM MDT and reaching 20 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.
EF065 to 85 mph
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
Unratedthis tornado
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
- Unrated
- Date
- August 19, 2024
- Touchdown
- 2:04 PM MDT (20:04 UTC)
- Lifted
- 2:07 PM MDT (20:07 UTC)
- On the ground
- 3 minutes
- Path length
- 0.6 miles (0.9 km)
- Path width
- 20 yards (18 m)
- Deaths
- 0
- Injuries
- 0
- County
- Adams County
- Touchdown point
- 39.890, -103.830
- Lift-off point
- 39.890, -103.819
- Record number
- 2408191404-01
What the Weather Service recorded
Severe thunderstorms developed along a convergence boundary that stretched from Limon to Sterling. The storms produce hail up to an inch and a half in diameter, winds to 60 mph, two landspout tornadoes and flash flooding.
Landspout tornado. Estimated to be 4-5 miles south/southeast of Prospect Rd and CR 152 in eastern Adams County. The tornado occurred over an open field with no damage.
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.
| Issued (UTC) | Expired | Product | Office |
|---|---|---|---|
| 20:15 UTC | 21:00 UTC | Severe Thunderstorm Warning | BOU |
| 20:57 UTC | 21:45 UTC | Severe Thunderstorm Warning | BOU |
| 21:36 UTC | 00:30 UTC | Flood Advisory | BOU |
| 21:41 UTC | 22:30 UTC | Severe Thunderstorm Warning | BOU |
| 21:53 UTC | 01:00 UTC | Flash Flood Warning | BOU |
| 01:01 UTC | 04:00 UTC | Flood Advisory | BOU |
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. The outlook in force was issued at 19:57 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.
N. Platte/Lee Bi, NE (KLBF), 12:00Z
8.1 hours before the tornado, 305 km from the path. August 19, 2024.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -87567 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- 1300 m above ground
- 0-6 km bulk shear
- 32 kt
- 0-1 km bulk shear
- 13 kt
- 0-1 km storm-relative helicity
- 53 m²/s²
- 0-3 km storm-relative helicity
- 94 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.2
- 0-3 km lapse rate
- 3.1 K/km
N. Platte/Lee Bi, NE (KLBF), 00:00Z
3.9 hours after it, 305 km from the path. August 20, 2024.
- Mixed-layer CAPE
- 677 J/kg
- Mixed-layer CIN
- -150 J/kg
- Surface CAPE
- 1199 J/kg
- Mixed-layer LCL
- 1245 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km bulk shear
- 7 kt
- 0-1 km storm-relative helicity
- 56 m²/s²
- 0-3 km storm-relative helicity
- 191 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.4
- 0-3 km lapse rate
- 7.1 K/km
The surface observations
Fort Morgan (FMM), 49 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 18:15 UTC | 84.2 | 69.8 | 90° 7 kt | 1023 | ||
| 18:35 UTC | 84.2 | 68 | 6 kt | 1023 | ||
| 18:55 UTC | 86 | 68 | 110° 9 kt | 15 | 1022.7 | |
| 19:15 UTC | 86 | 68 | 120° 11 kt | 1022.7 | ||
| 19:35 UTC | 87.8 | 68 | 70° 10 kt | 1022.4 | ||
| 19:55 UTC | 86 | 66.2 | 100° 7 kt | 12 | 1022 | |
| 20:15 UTC | 87.8 | 68 | 90° 9 kt | 1021.7 | ||
| 20:35 UTC | 89.6 | 66.2 | 100° 8 kt | 14 | 1021.3 | |
| 20:55 UTC | 87.8 | 66.2 | 100° 12 kt | 1021.3 | ||
| 21:15 UTC | 89.6 | 66.2 | 120° 11 kt | 17 | 1020.7 | |
| 21:35 UTC | 87.8 | 66.2 | 120° 17 kt | 22 | 1021.3 | |
| 21:55 UTC | 87.8 | 66.2 | 130° 17 kt | 22 | 1021.7 | VCTS |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Denver radar (KFTG), 63 km away, was scanning. The volume nearest the touchdown began at 20:04 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) | Report | Where | County | Remark |
|---|---|---|---|---|
| 20:04 UTC | TORNADO | 1 W Shamrock | Adams, CO | Landspout. Estimated to be 4-5 miles south/southeast of Prospect Rd and CR 152 in eastern Adams County. |
| 20:55 UTC | TORNADO | 10 Nne Deer Trail | Adams, CO | Location approximate. |
| 20:55 UTC | TORNADO | 10 Nne Deer Trail | Adams, CO | Updates tornado report from 10 NNE Deer Trail. Multiple spotters have confirmed location. Tornado lasted about 5-6 minutes. It remained nearly stationary for about 2 minutes, then slowly drifted westward. |
| 21:00 UTC | TSTM WND GST 60 | 8 S Shamrock | Adams, CO | |
| 21:03 UTC | TSTM WND DMG | 9 Sse Shamrock | Adams, CO | Large tree limb, 6 inches in diameter, snapped. Marble hail and torrential rain. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2024 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are
The other tornadoes of August 19, 2024
2 more were confirmed in the United States that day.
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.