Tornadoes · United States · Iowa · 2015

EF1 tornado, St Paul, Iowa, May 24, 2015

This EF1 tornado ran 0.1 miles across Lee County on May 24, 2015, touching down at 5:42 PM CDT and reaching 25 yards wide. It killed nobody, and did $10,000 of property damage.

The rating scale

Tracks are drawn in the color of the rating. The Enhanced Fujita scale rates the damage rather than measuring the wind: the speeds are what that damage is taken to imply.

  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.

The record

Rating
EF1
Date
May 24, 2015
Touchdown
5:42 PM CDT (22:42 UTC)
Path length
0.1 miles (0.2 km)
Path width
25 yards (23 m)
Deaths
0
Injuries
0
Property damage
$10,000
County
Lee County
Touchdown point
40.755, -91.480
Lift-off point
40.755, -91.480
Record number
1505241642-01

The damage survey

1 damage points were recorded along this path by NWS DVN, in the Damage Assessment Toolkit the survey teams carry. The strongest indicator was rated EF1. The highest wind the damage implies is 95 mph.

  • From EMA reports: Barn and a grain bin destroyed. Some trees and a power line were also blown down, and a couple of chimneys were damaged.

Survey points are preliminary and are the raw material the published rating was built from. Source: NWS Damage Assessment Toolkit.

What the Weather Service recorded

A weak warm front produced scattered showers and isolated thunderstorms. As the thunderstorms crossed north over the front, it spawned isolated tornadoes and funnel clouds in Des Moines County.

A brief tornado with wind estimated at 95 mph destroyed a barn and grain bin along Saint Paul Road. Some trees and a power line were also blown down. A couple of chimneys were damaged.

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

The warnings

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 22:36 UTC and running to 01:27 UTC.

Issued (UTC)ExpiredProductOffice
22:36 UTC01:27 UTCTornado WatchDVN

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 forecast that day

The Storm Prediction Center had this point in a Marginal Risk, with a 0.02 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 air that afternoon

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.

Davenport, (KDVN), 12:00Z

10.7 hours before the tornado, 126 km from the path. May 24, 2015.

Skew-T log-pSkew-T log-p diagram, Davenport, at 12:00Z on 2015-05-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 0 joules per kilogram, CIN -79336, lifted condensation level 1494 meters above ground. Wind barbs in knots down the right edge.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Davenport, at 12:00Z on 2015-05-24The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 175 square meters per square second, 0 to 6 km bulk shear 43 knots.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
-79336 J/kg
Surface CAPE
0 J/kg
Mixed-layer LCL
1494 m above ground
0-6 km bulk shear
43 kt
0-1 km bulk shear
22 kt
0-1 km storm-relative helicity
175 m²/s²
0-3 km storm-relative helicity
206 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0
0-3 km lapse rate
4.2 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 00:00Z

1.3 hours after it, 126 km from the path. May 25, 2015.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2015-05-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel lifted from the surface. Mixed-layer CAPE 210 joules per kilogram, CIN -41, lifted condensation level 1061 meters above ground. Wind barbs in knots down the right edge.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed. The warm shading is its CAPE, the cool shading the inhibition it has to break through.
HodographHodograph, Davenport, at 00:00Z on 2015-05-25The wind through the lowest 10 kilometers as a curve, rings every 10 meters per second labeled in knots. Zero to 1 km storm-relative helicity 192 square meters per square second, 0 to 6 km bulk shear 42 knots.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km. RM and LM are the right and left moving storms Bunkers' method gives; the shaded area is the 0 to 1 km storm-relative helicity.
Mixed-layer CAPE
210 J/kg
Mixed-layer CIN
-41 J/kg
Surface CAPE
1539 J/kg
Mixed-layer LCL
1061 m above ground
0-6 km bulk shear
42 kt
0-1 km bulk shear
31 kt
0-1 km storm-relative helicity
192 m²/s²
0-3 km storm-relative helicity
225 m²/s²
Significant tornado parameter
0.2
Supercell composite
6.0
0-3 km lapse rate
6.1 K/km

Open this sounding in Storm Lab

The radar

The Quad Cities radar (KDVN), 121 km away, was scanning. The volume nearest the touchdown began at 22:42 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.

What was reported nearby

Local storm reports within 60 km of the path, in the three hours either side.

Time (UTC)ReportWhereCountyRemark
20:20 UTCHEAVY RAIN 1.25 E CantrilVan Buren, IA
22:30 UTCTSTM WND DMG2 Ese St. PaulLee, IABARN BLOWN DOWN. POSSIBLE TORNADO.
22:30 UTCTORNADOWest PointLee, IAHOME ALONG SAINT PAUL ROAD WITH CHIMNEY BLOWN OFF OF THE HOME. THERE WAS TREE DAMAGE WITH A TREE BLOWN ON TO A PICKUP TRUCK, WITH FARM EQUIPMENT DAMAGED. TIME IS APPROXIMATED.

From the Iowa Environmental Mesonet's archive of National Weather Service local storm reports.

This ground now

The live radar over the trackEvery 2015 tornado in IowaEvery tornado in Iowa since 1950Warnings in force in Iowa nowThe forecast where you are

The other tornadoes of May 24, 2015

17 more were confirmed in the United States that day.

DateTimeRatingWherePath (mi)Width (yd)DeathsInjuriesDamage
May 241:27 AM CDTEF1Nueces, TX2.6100$750,000
May 242:34 AM CDTEF1Dallas, TX1.180$600,000
May 242:34 AM CDTEF1Dallas, TX4.940$100,000
May 246:33 AM CDTEF0Harris, TX0.5504$200,000
May 2411:34 AM CDTEF1Harrison, TX1.9128$75,000
May 2412:15 PM CDTEF1St. Clair, MO5.0200$400,000
May 244:45 PM MDTEF0Cherry, NE0.120
May 244:45 PM MDTEF0Cherry, NE0.120
May 245:59 PM CDTEF1Ozark, MO4.7200$75,000
May 246:50 PM CDTEF2Mercer, IL6.850$30,000
May 249:37 PM CDTEF1Seward, KS10.91,200$1.0 million
May 249:47 PM CDTEF0Seward, KS0.7150
May 2410:06 PM CDTEF0Meade, KS2.4100
May 2410:20 PM CDTEF0Meade, KS3.1100
May 2410:47 PM CDTEF1Meade, KS13.2800
May 2411:26 PM CDTEF2Meade, KS14.6250
May 2412:20 AM CDTEF1Ford, KS6.475

What this means

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.

Sources

NOAA Storm Prediction Center tornado database, 1950-2025, the official record kept by NOAA's Storm Prediction Center.