F0 tornado, St Marys, Iowa, June 25, 2000

1. F040 to 72 mphthis tornado

   Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.

2. F173 to 112 mph

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

3. F2113 to 157 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. F3158 to 206 mph

   Severe damage. Whole stories of well-built houses destroyed, large buildings badly damaged, trains overturned, trees debarked, heavy cars lifted and thrown.

5. F4207 to 260 mph

   Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.

6. F5261 to 318 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

F0

Date

June 25, 2000

Touchdown

5:22 PM CDT (22:22 UTC)

Path length

0.2 miles (0.3 km)

Path width

20 yards (18 m)

Deaths

0

Injuries

0

County

Warren County

Touchdown point

41.320, -93.730

Lift-off point

41.320, -93.730

Record number

255

A major wind and significant flash flooding event took shape across Iowa during the afternoon and evening of the 25th. A dynamic upper level system approached Iowa from the northwest during the afternoon. Several boundaries were in the area resulting from weak convection that took place during the morning. Very strong theta-e advection took place over northeast Nebraska during the morning and early afternoon hours. In addition, several other factors came into play. Moisture continued to stream into Iowa from the remnants of Hurricane Carlotta as precipitable water values approached 2.2 inches. Iowa was also under the influence of a coupled jet structure. As a result a strong upper level divergent field was in place over the state. By afternoon, mid and upper level cold air advection began to take place as well. Strong convection took place by mid day over northeast Nebraska into west central Iowa. The line of thunderstorms moved into rich air with surface dew points in the low to mid 70s. The main feature with the storms was high winds. The line of thunderstorms took on a bow echo configuration as it moved across southern Iowa. Most of the southern three tiers of counties reported high winds. Wind speeds of 60 to as much as 85 MPH were reported with the storms. Wind speeds topped out at 85 MPH at New Virginia, in Warren County. Damage was widespread with numerous trees and power lines downed by the winds. Some trees up to 2 feet in diameter were snapped. A flag pole was reported bent 4 inches by the high winds as well. One tornado was reported in Warren County as well. This was a brief tornado near St Marys which caused no damage. The other problem with the storms was the heavy rainfall. Two to three inches of rain fell in many areas. As the storms moved into parts of south central and southeast Iowa, they moved into area that had been inundated by heavy rainfall just two nights before. Flash flooding was reported in Appanoose, Lucas, Mahaska, Monroe, Wayne, Davis, and Wapello Counties. Numerous roads were under water in these counties. U.S. Highway 63 was closed by high water north of Ottumwa. Some of the worst flooding took place in Mahaska County where heavy rain fell on areas that had been flooded two days before. At least 15 roads were reported under water in the county. As the thunderstorms moved through Hamilton County, lightning struck a tree outside of a house in Stratford. It also left a hole in the ground and caused damage inside the house. The lightning strike broke windows out of the front of the house and also caused windows to break in the house next door. Later, the storms moved into the Waterloo area. Lightning struck the chimney of a former school building. The top part of the chimney was blown off by the lightning and a good part of the rest of the chimney was damaged.

Brief touchdown

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.

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 Moderate Risk. The outlook in force was issued at 20:14 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.

Des Moines (DSM), 25 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), 46 km away, was scanning. The volume nearest the touchdown began at 22:20 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.

The live radar over the trackEvery 2000 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

6 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.