EF0 tornado, Valeria to Newton Muni Arpt, Iowa, July 27, 2008

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

July 27, 2008

Touchdown

4:51 PM CDT (21:51 UTC)

Lifted

4:52 PM CDT (21:52 UTC)

On the ground

1 minutes

Path length

0.3 miles (0.4 km)

Path width

20 yards (18 m)

Deaths

0

Injuries

0

County

Jasper County

Touchdown point

41.736, -93.324

Lift-off point

41.733, -93.320

Record number

0807271551-01

A very unstable airmass was in place over Iowa as a warm front lifted north slowly into the state. The warm air had moved in aloft as freezing levels increased from 14,600 feet in the morning, to 16,200 by the evening hours. The atmosphere was a high CAPE, moderate to high shear with CAPE rising to near 5000 J/kg by late afternoon. Lifted indices fell to -8 to -13 C. A speed max moved across the state during the late afternoon and evening hours with shear increasing to between 45 and 60 kts. Downdraft CAPE was in the 1000 to 1400 J/kg range with available CAPE in the -10 to -30 C. layer of the atmosphere in the 800 to 1200 J/kg range. The LCL during the evening was around 1000 meters. A cluster of thunderstorms formed by the mid afternoon hours over northern Iowa. The storms propagated and grew to the southeast with all phases of severe weather occurring during the late afternoon and evening hours. Three tornadoes touched down. The strongest was in Polk County just southwest of Elkhart. The tornado damaged 2 houses and caused considerable tree damage. Parts of the house were blown up into the trees. The other touchdowns were relatively minor with one touching down briefly near Valeria in Jasper County, another just south of Newton in Jasper County. Straight line winds derailed 21 cars of a Burlington Northern train west of Albia. The storms formed into a forward propagating MCS and beta bow element before reaching central Iowa. An 82 MPH wind gust was recorded by a schoolnet site just east of Boone. There were numerous reports of winds to around 70 MPH as the storm moved south across the east side of Des Moines, and on southeast into southeast Iowa. Tree damage along the length of the bow echo was widespread with numerous uprooting reports, trees down, and power poles knocked down. In Poweshiek County, high winds north of Montezuma hit a farm. The barn was toppled completely. Surprisingly, a donkey that was in the barn walked out without a scratch. Most of the hail with the storm was around an inch in diameter. There was a report of 2 inch diameter hail in the New Virginia area of Warren County. Several golf ball size hail reports were received over southern Iowa as the air column cooled by the rainfall. Flash flooding became a problem in parts of southeast Iowa where rainfall of 2 to 3 inches fell in a short period of time. Many of these areas were areas that had been hit by heavy rainfall just a few days before. In Wayne County, 2 to 3 inches fell in parts of the northwest sections of the county, washing out a gravel road southwest of Derby. The storms moved southeast of the state by late evening...however thunderstorms re-fired in a line extending from near Ottumwa, through Ames, toward Fort Dodge. The storms produced hail and heavy rain with baseball size hail reported just south of Boone for example. Hail of 2.5 inches in diameter fell in Marion County at Knoxville as well. During the night, the storms continued to develop farther to the west. They produced hail up to golf ball and larger in size in Crawford. One storm produced softball size hail west of Kiron around sunrise. As the night progressed, the pattern transitioned to more heavy rain than severe weather. Flash flooding occurred as lines of thunderstorms trained across the same areas for a several hour period. Rainfall from the storms was anywhere from 3.5 to 7 inches in several areas with 6.73 inches in Guthrie Center one of the higher amounts. An unofficial report from near Brushy Creek, about 4 miles north of Guthrie Center, indicated rainfall of 8.3 inches. In Stuart, a report of 7 inches was received, while in the metro Des Moines area the highest total was 4.48 inches in Ankeny. River and stream flooding became a problem during the day on the 28th with several rivers reaching moderate flood stage. Major flooding occurred on Four Mile Creek in Des Moines.

Funnel visible nearly to the ground with circulation on the ground.

Brief touchdown just south of Newton.

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

8 minutes of warning. NWS DMX issued a tornado warning for this county at 21:43 UTC, 8 minutes before the tornado touched down, in force until 22:15 UTC.

The county was under a severe thunderstorm watch, issued at 19:30 UTC and running to 03:00 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 0.02 chance of a tornado within 25 miles. The outlook in force was issued at 19:49 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 Des Moines radar (KDMX), 33 km away, was scanning. The volume nearest the touchdown began at 21:51 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 2008 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

3 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.