EF1 tornado, Ayr to Page, North Dakota, May 30, 2007

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

May 30, 2007

Touchdown

5:30 PM CDT (22:30 UTC)

Lifted

5:40 PM CDT (22:40 UTC)

On the ground

10 minutes

Path length

5.0 miles (8.0 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

County

Cass County

Touchdown point

47.030, -97.415

Lift-off point

47.073, -97.500

Record number

0705301630-01

Late in the afternoon of the 30th, an area of surface low pressure was located along the North Dakota and South Dakota border south of Cayuga, ND. From this low, a warm front extended to the north-northeast, toward Fargo (ND) and then Fosston (MN). A cold front extended southeast from the low, down into southwest Minnesota. By early evening, the low had shifted northwest, and was located just southeast of Jamestown. Both the warm and cold fronts had also shifted to the north. A low in the mid levels of the atmosphere (500 mb) was also located just to the southwest of the surface low (along the ND/SD border southwest of Bismarck). This provided a ideal setup for a cold core tornado event.

Four 2400 bushel grain bins were destroyed. A motorhome was damaged and numerous tree branches were broken off in shelterbelts along the path. Peak tornadic winds were estimated at 100 to 105 mph.

Two funnels were reported near Page. One of them touched down just south of Page, then lifted briefly while it went over Page, then touched down repeatedly as it travelled northwest from Page. The tornado lifted about 3 miles south of Colgate. Peak tornadic winds were estimated at 90 to 95 mph. On the west edge of Page, a semi trailer was pushed along the ground, a grain elevator was flipped, and a satellite dish was ripped off a roof.

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. One was issued for the county at another hour that day.

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 General Thunderstorms Risk, with a 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 20:00 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.

Fargo (FAR), 51 km from the path, in the two hours either side.

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

The Fargo/Grand Forks radar (KMVX), 54 km away, was scanning. The volume nearest the touchdown began at 22:31 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.

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

1 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.