EF0 tornado, Ellston, Iowa, April 26, 2009

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

April 26, 2009

Touchdown

6:08 PM CDT (23:08 UTC)

Lifted

6:10 PM CDT (23:10 UTC)

On the ground

2 minutes

Path length

1.3 miles (2.1 km)

Path width

30 yards (27 m)

Deaths

0

Injuries

0

Property damage

$100,000

County

Ringgold County

Touchdown point

40.845, -94.077

Lift-off point

40.852, -94.053

Record number

0904261708-01

The warm front from the previous night lifted north of the state as low pressure pushed northeast out of Kansas across northwest Iowa. The atmosphere became quite unstable. Lifted indices fell to -6 to -8, with CAPE values in the 1000 to 2000 J/kg range. CAPE in the -10 to -30 C. layer of the atmosphere was between 200 and 500 J/kg. Downdraft CAPE was in the 400 to 700 J/kg range. The effective shear was between 35 and 55 kts. The freezing level was consistent with what it had been the previous few events, at 11,900 feet. Thunderstorms developed in several lines. The main issue with the thunderstorms was heavy rain as precipitable water values were around 1.6 inches. The 850 mb feed into the system was between 45 and 55 kts. Spotty reports of severe wind were received along the line with some relatively minor damage. Some farm outbuilding damage occurred with the high winds and a few trees were blown over. The roof and siding were both damaged on a house at Sun Valley Lake in Ringgold County as a brief tornado touched down there. Part of the roof was actually removed by 80 MPH straight line winds. Many of the storms produced hail, however it remained below severe limits. Flooding was widespread with flash flooding reported in several counties. Rainfall of 4 to 7 inches occurred in a few areas, especially in Guthrie and Audubon Counties. A band widespread 2 to 4 inch rainfall extended all the way across the CWA from the southwest corner to the northeast in the Waterloo area. Some of the heavier totals included 8.5 inches in Waterloo, 7.4 inches in Hudson, both in Black Hawk County, and 7 inches in Hardin County in the Whitten area. Numerous reports of 24 to 36 hour rainfall totals were received. They ranged from 3 1/4 to over 8 inches. As the thunderstorms were moving east of the area, lightning struck a house in Altoona setting it on fire. The house was severely damaged. Nobody was home at the time, however fire fighters were able to save the family dog.

Brief tornado about 1.25 miles long. Track about 30 miles wide. The EF0 rating was based on pictures and coordination with the Emergency Manager.

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 tornado watch, issued at 22:05 UTC and running to 23:59 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 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.

Lamoni (LWD), 28 km from the path, in the two hours either side.

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

The Des Moines radar (KDMX), 102 km away, was scanning. The volume nearest the touchdown began at 23:08 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

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.