EF2 tornado, Missouri Vly to Magnolia, Iowa, March 23, 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 mph

   Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.

3. EF2111 to 135 mphthis tornado

   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

EF2

Date

March 23, 2009

Touchdown

6:03 PM CDT (23:03 UTC)

Lifted

6:13 PM CDT (23:13 UTC)

On the ground

10 minutes

Path length

8.6 miles (13.8 km)

Path width

440 yards (402 m)

Deaths

0

Injuries

0

County

Harrison County

Touchdown point

41.550, -95.946

Lift-off point

41.673, -95.918

Record number

0903231703-01

An intense upper level low pressure system tracked from eastern Colorado into southeast South Dakota from March 23rd to March 24th. This caused a surface low pressure system to move from western Nebraska into southeast South Dakota during that time. As the low tracked northeast, a dry-line moved into eastern Nebraska during the afternoon of March 23rd. With surface temperatures in the 60s and 70s, and dewpoint temperatures in the 50s, ample instability was in place to allow a line of severe thunderstorms to develop as the dry-line punched eastward. Several fast moving and low-topped supercell thunderstorms were embedded in the line, and one cell produced cyclic tornadoes from southeast of Lincoln into western Iowa. The storms in the line were moving north northeast at between 50 and 60 mph. In addition to the severe weather, strong southerly gradient winds prevailed ahead of the low pressure. In some cases the winds gusted between 50 and 60 mph for several hours across parts of eastern Nebraska.

The tornado touched down near highway 30 about 1.5 miles west of the interchange between Interstate 29 and Highway 30, or about 3 miles west of Missouri Valley Iowa. The tornado was at its strongest and widest within a mile of its touchdown point, becoming weaker with more intermittent damage farther north. Near the touchdown point, a barn sustained roof damage and a windmill was knocked down. One-half mile north of Highway 30, 54 empty grain rail cars were derailed. One mile north of Highway 30, along 305th St., two residences were impacted by the tornado. A 100-year-old single family residence directly in its path was completely destroyed, with all walls collapsed and debris relocated about 50 feet north of the foundation. The debris collected over the site of a cinder block garage, which also partially collapsed. About 100 yards north of the garage site, a machine shed was collapsed onto a combine inside, which had been moved by the wind. Trees near the house sustained some broken limbs and treetops, and a power pole was snapped. The damage at this site was given an EF2 rating. Another residence one-quarter mile to its west sustained minor siding and shingle damage and windows were broken. Seven of the eight outbuildings at that residence were collapsed, with debris strewn into nearby fields. Damage at the two houses indicated a path width of one quarter mile at that point, the widest along the path of the tornado. The tornado continued northward, overturning two semis on Interstate 29. From there to a point about 3 miles southwest of Magnolia, near the intersection of the Loess Hills Trail and Melody Oaks Trail, intermittent light damage to trees and roofs of a couple of outbuildings was noted. From this point, the survey team determined the damage path narrowed to 100 yards or less based on scattered tree and outbuilding damage, with EF0 intensity north of Interstate 29.

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

28 minutes of warning. NWS OAX issued a tornado warning for this county at 22:35 UTC, 28 minutes before the tornado touched down, in force until 23:30 UTC.

The county was under a tornado watch, issued at 20:52 UTC and running to 00:53 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 19:42 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.

Blair (BTA), 26 km from the path, in the two hours either side.

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

The Omaha radar (KOAX), 49 km away, was scanning. The volume nearest the touchdown began at 23:03 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 2009 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

18 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.