EF1 tornado, Simla to Kutch, Colorado, June 4, 2015

1. EF065 to 85 mph

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. EF186 to 110 mphthis tornado

   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.

Rating

EF1

Date

June 4, 2015

Touchdown

6:17 PM MDT (00:17 UTC)

Lifted

6:24 PM MDT (00:24 UTC)

On the ground

7 minutes

Path length

2.0 miles (3.2 km)

Path width

300 yards (274 m)

Deaths

0

Injuries

0

County

Elbert County

Touchdown point

39.058, -104.043

Lift-off point

39.031, -104.031

Record number

1506041817-01

12 damage points were recorded along this path by NWS BOU and NWS PUB and NWS RAH, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 102 mph.

• some minor dog this location. we have no idea if building was dogs by tor or not
• small building damaged by the tornado.
• some minor damage this location. we have no idea if building was damaged by tor or not
• sign bent south-southeastward (160 degrees on the compass).

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

Severe thunderstorms broke out across Boulder, Denver, Elbert, Jefferson and Larimer Counties. Two large and long lived tornadoes developed in Larimer County near Berthoud and near Simla in Elbert County. The tornado that occurred along the Boulder and Larimer county line was rated an EF3 at it's highest damage point, with maximum winds estimated at 135 to 140 mph. The path length was 6 miles long with a width of one quarter mile at times. In Elbert County, 17 tornadoes touched down, with EF1 damage observed southwest and southeast of Simla. Four homes suffered severe damage; two were uninhabitable. In addition, two other homes suffered moderate damage with slight damage reported to eight other residences. Large hail up to baseball size occurred in Elbert County, with hail up to tennis ball size observed in Boulder County. The hail damaged cars and homes; breaking windows and windshields.

A tornado with an anticyclonic rotation touched down briefly but did no damage.

A tornado touched down and destroyed a pole barn.

A tornado touched down in open country. No damage was observed.

A tornado touched down in open country. No damage was observed.

A well defined tornado touched down and produced some property damage at a farmstead. The home, barn and nearby outbuildings sustained damage. A power pole was also snapped about 5 feet above the ground.

Two tornadoes touched down in close proximity to one another, one of which was anticyclonic. Both occurred in open country so no damage was observed.

A well defined tornado touched down in open country. No damage was observed.

A tornado touched down in open country. No damage was observed.

A well defined tornado touched down in open country. No damage was observed.

An anticyclonic tornado touched down in open country. No damage was observed.

A tornado touched down in open country. No damage was observed.

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

19 minutes of warning. NWS BOU issued a tornado warning for this county at 23:58 UTC, 19 minutes before the tornado touched down, in force until 00:30 UTC.

The county was under a tornado watch, issued at 20:21 UTC and running to 04:00 UTC.

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 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 20:06 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 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.

Ellicott-B Afa (ABH), 40 km from the path, in the two hours either side.

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

The Pueblo radar (KPUX), 66 km away, was scanning. The volume nearest the touchdown began at 00:19 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.

Local storm reports within 60 km of the path, in the three hours either side.

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

The live radar over the trackEvery 2015 tornado in ColoradoEvery tornado in Colorado since 1950Warnings in force in Colorado nowThe forecast where you are

19 more were confirmed in the United States that day.

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.

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.