Tornadoes · United States · Colorado · 2009

EF0 tornado, Pierce to Nunn, Colorado, June 22, 2009

From Pierce to Nunn, this EF0 tornado ran 0.1 miles across Weld County on June 22, 2009, touching down at 10:10 PM MDT and reaching 50 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
June 22, 2009
Touchdown
10:10 PM MDT (04:10 UTC)
Path length
0.1 miles (0.2 km)
Path width
50 yards (46 m)
Deaths
0
Injuries
0
County
Weld County
Touchdown point
40.670, -104.810
Lift-off point
40.670, -104.810
Record number
0906222210-01

What the Weather Service recorded

Severe thunderstorms produced large hail across Boulder, Larimer and Weld Counties. Hail up to 2 inches in diameter was observed in Boulder County. Crop damage was observed near Wellington. Very heavy rain produced flash flooding in parts of Fort Collins, Laporte, Livermore and Wellington. Two weak tornadoes also touched down.

A small tornado touched down but did no damage.

A small tornado touched down but did no damage.

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

The warnings

16 minutes of warning. NWS BOU issued a tornado warning for this county at 03:54 UTC, 16 minutes before the tornado touched down, in force until 04:45 UTC.

Issued (UTC)ExpiredProductOffice
02:51 UTC03:45 UTCSevere Thunderstorm WarningBOU
03:34 UTC06:30 UTCFlash Flood WarningBOU
03:44 UTC04:45 UTCSevere Thunderstorm WarningBOU
03:54 UTC04:45 UTCTornado WarningBOU
04:24 UTC05:00 UTCTornado WarningBOU
04:32 UTC05:04 UTCSevere Thunderstorm WarningBOU
04:57 UTC05:45 UTCSevere Thunderstorm WarningBOU
05:57 UTC06:13 UTCSevere Thunderstorm WarningBOU
20:51 UTC03:00 UTCSevere Thunderstorm WatchBOU
22:02 UTC23:00 UTCSevere Thunderstorm WarningBOU

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 General Thunderstorms Risk. The outlook in force was issued at 01:02 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 (KDNR), 00:00Z

4.2 hours before the tornado, 161 km from the path. June 23, 2009.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 00:00Z on 2009-06-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 322 joules per kilogram, CIN -23, lifted condensation level 3111 meters above ground. Wind barbs in knots down the right edge.LCLEL10008507005003002001001 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 2009-06-23The 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 92 square meters per square second, 0 to 6 km bulk shear 45 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
322 J/kg
Mixed-layer CIN
-23 J/kg
Surface CAPE
878 J/kg
Mixed-layer LCL
3111 m above ground
0-6 km bulk shear
45 kt
0-1 km bulk shear
12 kt
0-1 km storm-relative helicity
92 m²/s²
0-3 km storm-relative helicity
134 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.9
0-3 km lapse rate
9.9 K/km

Open this sounding in Storm Lab

Denver, CO (KDNR), 12:00Z

7.8 hours after it, 161 km from the path. June 23, 2009.

Skew-T log-pSkew-T log-p diagram, Denver, CO at 12:00Z on 2009-06-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 730 joules per kilogram, CIN -272, lifted condensation level 1043 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 2009-06-23The 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 -58 square meters per square second, 0 to 6 km bulk shear 31 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
730 J/kg
Mixed-layer CIN
-272 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1043 m above ground
0-6 km bulk shear
31 kt
0-1 km bulk shear
11 kt
0-1 km storm-relative helicity
-58 m²/s²
0-3 km storm-relative helicity
-5 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1
0-3 km lapse rate
4.0 K/km

Open this sounding in Storm Lab

The radar

The Cheyenne radar (KCYS), 54 km away, was scanning. The volume nearest the touchdown began at 04:08 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
03:12 UTCHAIL 12 S LaporteLarimer, CO
03:22 UTCHAIL 13 Ne Fort CollinsLarimer, CO
03:23 UTCHAIL 12 Nw Fort CollinsLarimer, COHEAVY RAIN WITH STREET FLOODING.
03:25 UTCHAIL 0.754 N Fort CollinsLarimer, CO
03:45 UTCFLASH FLOOD2 Nw Fort CollinsLarimer, COMAJOR STREET FLOODING. 1.17 INCHES RAIN SO FAR.
03:47 UTCHAIL 0.75BellvueLarimer, CO
03:47 UTCTORNADO4 W PierceWeld, CO
04:02 UTCFLASH FLOODWellingtonLarimer, COSTREET FLOODING.
04:10 UTCTORNADO4 Nw PierceWeld, CO
04:15 UTCFLASH FLOODWellingtonLarimer, COSTREET FLOODING CONTINUES.
04:15 UTCHAIL 1WellingtonLarimer, CO
04:17 UTCFLASH FLOODN LivermoreLarimer, COON TAFT HILL RD.
04:19 UTCHAIL 16 W NunnWeld, CO
04:39 UTCHEAVY RAIN 2.54 E WellingtonWeld, CO

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 ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

The other tornadoes of June 22, 2009

1 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
June 229:47 PM MDTEF0Weld, CO0.150

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.