EF0 tornado, Napoleon, North Dakota, August 26, 2007

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.

Rating

EF0

Date

August 26, 2007

Touchdown

8:35 PM CDT (01:35 UTC)

Lifted

8:40 PM CDT (01:40 UTC)

On the ground

5 minutes

Path length

1.0 miles (1.6 km)

Path width

35 yards (32 m)

Deaths

0

Injuries

0

Crop damage

$5,000

County

Logan County

Touchdown point

46.551, -99.696

Lift-off point

46.561, -99.681

Record number

0708261935-01

In the late afternoon of Sunday, August 26th, Tornado Watch 653 was issued in anticipation of severe thunderstorms developing ahead of a cold front situated across western North Dakota. Strong low level wind shear ahead of the front and MLCAPE values near 3500 j/kg increased the potential for tornadic supercells. Logan County was hit especially hard.

Public reported tornado touched down four times along this path. Tornado lifted to a funnel cloud and then touched down repeatedly. NWS storm damage survey also indicated this as the evidence was sporadic along the path, indicating the tornado was not on the ground the entire time / length. No structures impacted. Damage to crops. See the second tornado entry for Logan County August 26 for the same supercell storm. Also see the large hail entry, again from the same supercell.

Damage to trees and hay and straw bales. Bales were blown a few hundred feet. NWS storm damage survey completed. No structures impacted. See the first tornado entry for Logan County August 26 for the same supercell storm. Also see the large hail entry, again from the same supercell.

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

8 minutes of warning. NWS BIS issued a tornado warning for this county at 01:27 UTC, 8 minutes before the tornado touched down, in force until 02:00 UTC.

The county was under a tornado watch, issued at 22:13 UTC and running to 03:49 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 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 00:53 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.

Bismarck (BIS), 84 km from the path, in the two hours either side.

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

The Bismarck radar (KBIS), 85 km away, was scanning. The volume nearest the touchdown began at 01:34 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 2007 tornado in North DakotaEvery tornado in North Dakota since 1950Warnings in force in North Dakota nowThe forecast where you are

10 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.