EF1 tornado, Minnetrista to Plymouth, Minnesota, August 8, 2009

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

August 8, 2009

Touchdown

8:33 PM CDT (01:33 UTC)

Lifted

8:49 PM CDT (01:49 UTC)

On the ground

16 minutes

Path length

9.1 miles (14.7 km)

Path width

200 yards (183 m)

Deaths

0

Injuries

0

Property damage

$1.0 million

County

Hennepin County

Touchdown point

44.963, -93.669

Lift-off point

45.008, -93.493

Record number

0908081933-01

The evening of August 8th, a very unstable air mass was in place across the upper Midwest with a warm front draped across the Twin Cities area, then eastward across west central Wisconsin. Initially, a strong cap suppressed thunderstorm development until around sunset as a cool front moved across east central Minnesota, and developed a supercell in the western part of Hennepin County. The supercell moved across the northern Twin Cities metro, then into Wisconsin.

A damage survey determined that an EF1 tornado touched down in the northeast side of Minnetrista, or on the west side of the intersection of County Road 110, and 151. The tornado tracked east-northeast for approximately nine miles to the east side of County Road 101, or at Garland and 25th which is in the southwest portion of Plymouth. Numerous trees were snapped and dozens of other trees fell on homes and vehicles. Boats were tossed and roofs were partially removed from two homes and a business.

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

NWS Twin Cities, MN wrote its last area forecast discussion before the tornado touched down at Aug 8, 6:32 PM CDT, 2 hours 1 minute earlier.

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In the hours before

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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.

Minneapolis - Crystal (MIC), 20 km from the path, in the two hours either side.

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

The Minneapolis radar (KMPX), 15 km away, was scanning. The volume nearest the touchdown began at 01:31 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.

The live radar over the trackEvery 2009 tornado in MinnesotaEvery tornado in Minnesota since 1950Warnings in force in Minnesota nowThe forecast where you are

3 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.