EF1 tornado, Tripoli, Iowa, June 23, 2010

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 23, 2010

Touchdown

2:18 AM CDT (07:18 UTC)

Lifted

2:19 AM CDT (07:19 UTC)

On the ground

1 minutes

Path length

0.3 miles (0.5 km)

Path width

35 yards (32 m)

Deaths

0

Injuries

0

Property damage

$10,000

County

Bremer County

Touchdown point

42.804, -92.313

Lift-off point

42.804, -92.308

Record number

1006230118-01

A very unstable airmass was in place over Iowa during the late afternoon and evening of the 22nd. Surface temperatures warmed into the upper 80s to low 90s over much of the state with dew point temperatures rising into the mid 70s to low 80s. CAPE values increased to over 6000 J/kg over the southern half of the state with lifted indices around -12 C. Deep moisture flowed into the state both at low levels as well with the presence of a prominent tropical feed on the water vapor satellite imagery. Precipitable water values increased to 1.8 to 2.2 inches over southern Iowa as moisture pooled. Significant shear was present with effective shear of 45 to 60 kts over northern Iowa. Downdraft CAPE was over 1000 J/kg, while the available CAPE in the -10 to -30 C layer of the atmosphere was in the 800 to 1200 J/kg range. Hail was somewhat limited however with the freezing level between 14,500 and 15,500 feet. Temperatures at the 700 mb level rose to +15 C over southwest Iowa by evening. A strong upper level shortwave lifted northeast out of Colorado during the overnight into the early morning hours of the 22nd into the 23rd. A cold front approached Iowa from the northwest and moved into the northwestern counties by sunrise on the 23rd. Thunderstorms were slow to develop initially due to a strong cap in place over the state. After sunset, explosive development took place over northwest into north central Iowa. Several tornadoes touched down over northern Iowa. None of them were on the ground for an extended period of time however. One touched down in the Sac City area of Sac County, another in Humboldt west of Humboldt. A third tornado was on the ground for a few minutes in the Eagle Grove area. A brief touchdown occurred in Franklin County north of Iowa Falls. A tornado touched down just west of Tripoli. It obliterated an abandoned barn with a brief touchdown. The tornado was one of the stronger of the day at EF1 strength. Funnel clouds were numerous in spite of the darkness due to the vivid lightning and the ability to see them. There were several hail reports, with some of the hail reaching golf ball in size in Winnebago and Kossuth Counties. High winds were a more significant problem with the event as it developed in to an upscale MCC. Numerous reports of downed trees and power lines were received. A semi was overturned on I-35 at milepost 154 by high wind, with another 10 miles farther north. Damage to homes and barns was reported in Bremer and Black Hawk Counties as well. One storm produced a narrow microburst just west of Tripoli with winds estimated at 95 to 100 MPH based on a NWS storm survey. Three homes were damaged with 2 of them serious. Some outbuildings were also damaged by this microburst. The storms also produced very heavy rainfall. Flash flooding took place in several counties, including Wright, Franklin, and Palo Alto. Extensive street flooding took place in Clarion in Wright County with power out in most of the city. In addition, U.S. Highway 69 and Iowa Highway 3 were under water. U.S. Highway 18 was overtopped by high water in 2 places between Spencer and Emmetsburg in Palo Alto County. Roads were under water near Sheffield in Franklin County. Rainfall was heavy with amounts of 4 to 7 inches reported in a band extending from eastern Palo Alto, through Humboldt and Wright Counties, into Franklin County. Heavy rain flooded roads and resulted in evacuations in the town of Dumont in Butler County. The rain fell in just a few hours time. Following the flash flooding, areal flooding continued in parts of the area with highways remaining closed. Some local flooding was also reported in Warren County, east of the Carlisle area.

Tornado was about 35 miles wide with a path of 500 yards. An abandon farm building was totally destroyed.

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

No tornado warning for this county appears in the archive as in force at the moment the tornado touched down.

The county was under a severe thunderstorm watch, issued at 02:00 UTC and running to 11:00 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 06:00 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.

Waterloo (ALO), 29 km from the path, in the two hours either side.

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

The La Crosse radar (KARX), 145 km away, was scanning. The volume nearest the touchdown began at 07:18 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 2010 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

11 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.