EF1 tornado, Stanley, Iowa, August 19, 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 19, 2009

Touchdown

4:30 PM CDT (21:30 UTC)

Lifted

4:45 PM CDT (21:45 UTC)

On the ground

15 minutes

Path length

2.2 miles (3.5 km)

Path width

100 yards (91 m)

Deaths

0

Injuries

0

Property damage

$75,000

County

Buchanan County

Touchdown point

42.615, -91.819

Lift-off point

42.635, -91.785

Record number

0908191530-01

Late morning and early afternoon sunshine was the fuel for a couple rounds of showers and thunderstorms across the region August 19. The storms brought heavy rain to most areas, with rainfall amounts between a half inch and and inch and a half common. In addition, tornadoes were reported from central Illinois all the way up to the Twin Cities. This included touchdowns near Stanley and Martelle, IA. With all of the cloud cover during the afternoon, high temperatures only topped out in the upper 70s to lower 80s.

An EF1 tornado touched down about 2.5 miles south of Stanley, IA around 430 pm August 19. It tracked to the northeast for about 2.2 miles before lifting about 2.1 miles east southeast of Stanley, IA around 445 pm. Wind speeds were estimated to be around 95 mph. Two farmsteads sustained damage. Two hog confinements were damaged. A residence lost most of its roof. A silo was damaged. The back wall of a pole building was blown out and trees were blown down.

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 Slight Risk, with a 0.05 chance of a tornado within 25 miles. The outlook in force was issued at 21:34 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.

The La Crosse radar (KARX), 142 km away, was scanning. The volume nearest the touchdown began at 21:30 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

29 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.