Tornadoes · United States · Utah · 2009

EF0 tornado, Leota, Utah, August 6, 2009

This EF0 tornado ran 2.2 miles across Uintah County on August 6, 2009, touching down at 4:10 PM MDT and reaching 25 yards wide. It killed nobody, and did $40,000 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 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 6, 2009
Touchdown
4:10 PM MDT (22:10 UTC)
Lifted
4:20 PM MDT (22:20 UTC)
On the ground
10 minutes
Path length
2.2 miles (3.5 km)
Path width
25 yards (23 m)
Deaths
0
Injuries
0
Property damage
$40,000
County
Uintah County
Touchdown point
40.187, -109.701
Lift-off point
40.199, -109.663
Record number
0908061610-01

What the Weather Service recorded

Strong thunderstorms produced severe weather events across northwest Utah.

A tornado was observed by a number of people in the Pelican Lake area. The tornado was first seen as it came up over a hill just west of Pelican Lake. The tornado then traveled across Pelican Lake and turned white as it pick up water off the lake. On the east shore of the lake, the tornado tore up some trees and flipped over a trailer used for living quarters at a man camp. Nobody was in the trailer at the time of the event.

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)ExpiredProductOffice
22:03 UTC22:30 UTCSevere Thunderstorm WarningGJT
22:28 UTC23:15 UTCSevere Thunderstorm WarningGJT
02:18 UTC11:52 UTCFlood AdvisoryGJT

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

10.2 hours before the tornado, 156 km from the path. August 6, 2009.

Skew-T log-pSkew-T log-p diagram, Grand Junction, CO at 12:00Z on 2009-08-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -51302, lifted condensation level 2876 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Grand Junction, CO at 12:00Z on 2009-08-06The 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 77 square meters per square second, 0 to 6 km bulk shear 33 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
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

Open this sounding in Storm Lab

Grand Junction, CO (KGJT), 00:00Z

1.8 hours after it, 156 km from the path. August 7, 2009.

Skew-T log-pSkew-T log-p diagram, Grand Junction, CO at 00:00Z on 2009-08-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -70695, lifted condensation level 3790 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 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, Grand Junction, CO at 00:00Z on 2009-08-07The 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 116 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
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

Open this sounding in Storm Lab

The surface observations

Vernal (VEL), 31 km from the path, in the two hours either side.

Time (UTC)Temp (°F)Dew point (°F)WindGust (kt)Pressure (mb)Weather
20:53 UTC80490° 0 kt1014.9
21:53 UTC8049280° 4 kt1012.9VCTS
22:14 UTC80.648.2340° 6 kt1012.5VCTS
22:34 UTC62.651.8210° 16 kt401016.3+TSRA
22:46 UTC60.853.620° 9 kt1012.5-TSRA
22:53 UTC6355330° 8 kt1012.9VCTS
23:02 UTC64.455.4310° 6 kt1012.5
23:53 UTC705660° 9 kt1011.9

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

The radar

The Grand Junction radar (KGJX), 178 km away, was scanning. The volume nearest the touchdown began at 22:09 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
22:20 UTCTSTM WND GST 60RandlettUintah, UTHEAVY RAIN AND DIME SIZE HAIL ALSO REPORTED WITH THIS STORM.
22:22 UTCHAIL 13 Sse VernalUintah, UTTRAINED SPOTTER REPORTED QUARTER-SIZED HAIL.
22:25 UTCHAIL 1NaplesUintah, UTSOME WINDOWS BROKEN BY STRONG WIND-DRIVEN HAIL.
22:25 UTCHAIL 1NaplesUintah, UTTRAINED SPOTTER REPORTED QUARTER-INCH HAIL.
22:25 UTCHAIL 1.751 Ssw NaplesUintah, UTMOSTLY 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.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
August 65:39 PM MDTEF0Uintah, UT0.520$1,000

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.