Tornadoes · United States · Utah · 2009
EF0 tornado, Vernal, Utah, August 6, 2009
This EF0 tornado ran 0.5 miles across Uintah County on August 6, 2009, touching down at 5:39 PM MDT and reaching 20 yards wide. It killed nobody, and did $1,000 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.
EF065 to 85 mphthis tornado
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.
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 6, 2009
- Touchdown
- 5:39 PM MDT (23:39 UTC)
- Lifted
- 5:42 PM MDT (23:42 UTC)
- On the ground
- 3 minutes
- Path length
- 0.5 miles (0.8 km)
- Path width
- 20 yards (18 m)
- Deaths
- 0
- Injuries
- 0
- Property damage
- $1,000
- County
- Uintah County
- Touchdown point
- 40.449, -109.538
- Lift-off point
- 40.453, -109.530
- Record number
- 0908061739-01
What the Weather Service recorded
Strong thunderstorms produced severe weather events across northwest Utah.
A tornado tracked through a small section of Vernal, mostly staying between houses. A number of trees had large limbs broken off and some minor damage occurred to sheds. The tornado was seen by many area residents and photographed by at least three persons.
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 |
|---|---|---|---|
| 22:03 UTC | 22:30 UTC | Severe Thunderstorm Warning | GJT |
| 22:28 UTC | 23:15 UTC | Severe Thunderstorm Warning | GJT |
| 02:18 UTC | 11:52 UTC | Flood Advisory | GJT |
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 20:03 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.
Grand Junction, CO (KGJT), 12:00Z
11.7 hours before the tornado, 171 km from the path. August 6, 2009.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -51302 J/kg
- Surface CAPE
- 0 J/kg
- Mixed-layer LCL
- 2876 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km bulk shear
- 11 kt
- 0-1 km storm-relative helicity
- 77 m²/s²
- 0-3 km storm-relative helicity
- 175 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
- 0-3 km lapse rate
- 7.1 K/km
Grand Junction, CO (KGJT), 00:00Z
0.3 hours after it, 171 km from the path. August 7, 2009.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- -70695 J/kg
- Surface CAPE
- 323 J/kg
- Mixed-layer LCL
- 3790 m above ground
- 0-6 km bulk shear
- 41 kt
- 0-1 km bulk shear
- 18 kt
- 0-1 km storm-relative helicity
- 116 m²/s²
- 0-3 km storm-relative helicity
- 118 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
- 0-3 km lapse rate
- 9.2 K/km
The surface observations
Vernal (VEL), 2 km from the path, in the two hours either side.
| Time (UTC) | Temp (°F) | Dew point (°F) | Wind | Gust (kt) | Pressure (mb) | Weather |
|---|---|---|---|---|---|---|
| 21:53 UTC | 80 | 49 | 280° 4 kt | 1012.9 | VCTS | |
| 22:14 UTC | 80.6 | 48.2 | 340° 6 kt | 1012.5 | VCTS | |
| 22:34 UTC | 62.6 | 51.8 | 210° 16 kt | 40 | 1016.3 | +TSRA |
| 22:46 UTC | 60.8 | 53.6 | 20° 9 kt | 1012.5 | -TSRA | |
| 22:53 UTC | 63 | 55 | 330° 8 kt | 1012.9 | VCTS | |
| 23:02 UTC | 64.4 | 55.4 | 310° 6 kt | 1012.5 | ||
| 23:53 UTC | 70 | 56 | 60° 9 kt | 1011.9 | ||
| 00:53 UTC | 72 | 54 | 40° 8 kt | 1011.2 |
From the Iowa Environmental Mesonet's archive of airport observations.
The radar
The Grand Junction radar (KGJX), 191 km away, was scanning. The volume nearest the touchdown began at 23:39 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 |
|---|---|---|---|---|
| 22:20 UTC | TSTM WND GST 60 | Randlett | Uintah, UT | HEAVY RAIN AND DIME SIZE HAIL ALSO REPORTED WITH THIS STORM. |
| 22:22 UTC | HAIL 1 | 3 Sse Vernal | Uintah, UT | TRAINED SPOTTER REPORTED QUARTER-SIZED HAIL. |
| 22:25 UTC | HAIL 1 | Naples | Uintah, UT | SOME WINDOWS BROKEN BY STRONG WIND-DRIVEN HAIL. |
| 22:25 UTC | HAIL 1 | Naples | Uintah, UT | TRAINED SPOTTER REPORTED QUARTER-INCH HAIL. |
| 22:25 UTC | HAIL 1.75 | 1 Ssw Naples | Uintah, UT | MOSTLY ONE INCH DIAMETER. LARGEST HAIL STONES WERE GOLF BALL SIZED. |
From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.
This ground now
The live radar over the trackEvery 2009 tornado in UtahEvery tornado in Utah since 1950Warnings in force in Utah nowThe forecast where you are
The other tornadoes of August 6, 2009
1 more were confirmed in the United States that day.
| Date | Time | Rating | Where | Path (mi) | Width (yd) | Deaths | Injuries | Damage |
|---|---|---|---|---|---|---|---|---|
| August 6 | 4:10 PM MDT | EF0 | Uintah, UT | 2.2 | 25 | $40,000 |
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.