Tornadoes · United States · Iowa · 2007

EF0 tornado, Castle Hill, Iowa, June 21, 2007

Name: EF0 tornado, Castle Hill, Iowa, June 21, 2007
Start: 2007-06-21T22:22:00.000Z
Location: Castle Hill, Iowa

This EF0 tornado ran 0.1 miles across Black Hawk County on June 21, 2007, touching down at 5:22 PM CDT and reaching 30 yards wide. It killed nobody.

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.

EF065 to 85 mphthis tornado
Light damage. Surface peeled off some roofs, gutters and siding damaged, branches broken, shallow-rooted trees pushed over.
EF186 to 110 mph
Moderate damage. Roofs badly stripped, mobile homes overturned or badly damaged, exterior doors lost, windows broken.
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.
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.
EF4166 to 200 mph
Devastating damage. Well-built houses leveled, structures with weak foundations moved some distance, cars thrown and large missiles generated.
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.
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: EF0
Date: June 21, 2007
Touchdown: 5:22 PM CDT (22:22 UTC)
Path length: 0.1 miles (0.2 km)
Path width: 30 yards (27 m)
Deaths: 0
Injuries: 0
Crop damage: $2,000
County: Black Hawk County
Touchdown point: 42.500, -92.410
Lift-off point: 42.500, -92.410
Record number: 0706211622-01

What the Weather Service recorded

A warm, moist, and unstable airmass was in place over Iowa on the afternoon of the 21st. A Warm front lifted north into the state with temperatures rising into the upper 80s to low 90s south of it with dew point temperatures in the upper 60s to low 70s. This combination produced most unstable CAPE values in the 3000 to 4000 J/kg range and lifted indices in the -9 C. range. The environment was not strongly sheared with 25 to 35 kts of effective shear. The freezing level was quite high at 14,700 feet. In spite of this, there was plenty of cape in the -10 to -30 C. layer of the atmosphere, with 500 J/kg available. The LFC in the 1200 to 2000 meter range. The MCS developed rapidly and move east-southeast across Iowa. Many of the storms produced significant hail, with hail size ranging from nickel to over tennis ball size. Two and one half inch diameter hail fell north of Renwick in Humboldt County. Golf ball size hail fell in Hancock County in the Corwith area. The largest hail occurred during the first couple hours of the systems development. Most of the hail was in the three quarter to one inch diameter range later on. Four tornadoes were reported with the system. All of the were brief touchdowns however and caused little damage. One touched down in Wright County near Eagle Grove. Two others touched down in Butler County one west of Shell Rock, the other north of Steamboat Rock. The fourth tornado touched down northwest of Kelly in Story County. The final tornado touched down on the south side of Waterloo in Black Hawk County. Many of the storms produced strong winds of at least 45 to 50 MPH. There were several reports of winds in excess of 60 MPH however. Numerous trees were blown down and a few power poles snapped. Winds caused damage in the Poweshiek County with winds estemated at near 80 MPH.

Brief touchdown with no significant damage.

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

What forecasters said that day

The local office's own words before the tornado touched down, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before the tornado touched down at Jun 21, 3:10 PM CDT, 2 hours 12 minutes earlier.

Area forecast discussion, Jun 21, 3:10 PM CDT, 2 hours 12 minutes before

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
310 PM CDT THU JUN 21 2007

.DISCUSSION...

TOO BUSY HERE...SHORT AFTER TODAYS RAIN WARM AND MOSTLY DRY THOUGH
MID WEEK MODELS PUSHING FRONTAL SYSTEM THROUGH THE UPPER MIDWEST
WITH CHANCE POPS.
&&

.AVIATION 22/18Z...

PRESENT CONCERNS WILL REMAIN WITH STRONG THUNDERSTORMS ACROSS MUCH
OF THE AREA. EXPECT SVR STORMS TO CONTINUE THROUGH THE EVENING HOURS
WITH +TSRA AND VISBYS UNDER 1 MILE AT TIMES. CIGS LOWERING TO
OVC010-020 WITH TSRA AND SHRA ACTIVITY. EXPECT ACTIVITY TO REMAIN IN
AREA THROUGH 08Z CENTRAL AND 12Z IN THE SOUTH.

&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

 LONG TERM...FORSTER/71/47/15
AVIATION/SHORT TERM...REV

Hazardous weather outlook, Jun 21, 11:35 AM CDT, 5 hours 47 minutes before

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1135 AM CDT THU JUN 21 2007

IAZ004>007-015>017-023>028-033>039-044>050-057>062-074-075-221100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-MARION-MAHASKA-
1135 AM CDT THU JUN 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
NORTH CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A MODERATE RISK FOR SEVERE WEATHER THIS AFTERNOON AND
TONIGHT. THUNDERSTORMS ARE EXPECTED THIS AFTERNOON...PRIMARILY
INCREASING IN COVERAGE THROUGH THE EVENING AND TONIGHT. GOLF BALL
SIZED HAIL...80 MPH WINDS AND ISOLATED TORNADOES ARE ALL POSSIBLE
BETWEEN 2 PM AND MIDNIGHT. QUARTER SIZED HAIL AND 60 MPH WINDS WILL
REMAIN A THREAT AFTER MIDNIGHT.

IN ADDITION...HEAVY RAINFALL OF 1 TO 3 INCHES IS POSSIBLE. LOCALLY
HIGHER AMOUNTS CAN NOT BE RULED OUT. THESE RAINFALL AMOUNTS WHICH
MAY FALL OVER A SHORT PERIOD OF TIME COULD PRODUCE LOCAL FLASH
FLOODING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE THREAT FOR VERY HEAVY RAINFALL WILL CONTINUE FRIDAY AND FRIDAY
NIGHT. TOTAL RAINFALL AMOUNTS FROM TONIGHT THROUGH SATURDAY
MORNING OF 2 TO 4 INCHES WITH ISOLATED AMOUNTS OVER 5 INCHES ARE
EXPECTED. FLASH FLOODING AND SIGNIFICANT RISES ON AREA RIVERS AND
STREAMS WOULD BE LIKELY IF THESE AMOUNTS VERIFY.

A SLIGHT RISK FOR SEVERE WEATHER IS FORECAST FOR FRIDAY AND FRIDAY
NIGHT WITH QUARTER SIZED HAIL AND 60 MPH WINDS POSSIBLE.

THUNDERSTORMS WILL LINGER INTO EARLY SATURDAY HOWEVER NO SEVERE
WEATHER IS ANTICIPATED.

.SPOTTER INFORMATION STATEMENT...

ATTENTION EMERGENCY MANAGERS...A CONFERENCE CALL WILL BE CONDUCTED
AT 1 PM THIS THURSDAY AFTERNOON.

SPOTTER ACTIVATION IS EXPECTED THIS AFTERNOON AND TONIGHT ESPECIALLY
BETWEEN 3 PM AND MIDNIGHT. ACTIVATION IS POSSIBLE AGAIN OF FRIDAY.
RAINFALL REPORTS WOULD BE GREATLY APPRECIATED DURING THE PERIOD AS
WELL.

IAZ070>073-081>086-092>097-221100-
CASS-ADAIR-MADISON-WARREN-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO-
TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS-
1135 AM CDT THU JUN 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
IOWA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A CHANCE FOR THUNDERSTORMS LATER THIS AFTERNOON AND
TONIGHT. A FEW STORMS MAY BE SEVERE WITH QUARTER SIZED HAIL AND 60
MPH WINDS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE IS A SLIGHT RISK FOR SEVERE WEATHER ON FRIDAY ESPECIALLY
DURING THE AFTERNOON AND EVENING HOURS. GOLF BALL SIZED HAIL AND
65 MPH WINDS ARE THE PRIMARY THREATS THOUGH AN ISOLATED TORNADO IS
POSSIBLE. HEAVY RAINFALL OF 1 TO 3 INCHES IS ALSO A THREAT.

THUNDERSTORMS WILL LINGER INTO SATURDAY THOUGH NO SEVERE WEATHER
IS EXPECTED.

.SPOTTER INFORMATION STATEMENT...

ATTENTION EMERGENCY MANAGERS...A CONFERENCE CALL WILL BE CONDUCTED
AT 1 PM THIS THURSDAY AFTERNOON.

SPOTTER ACTIVATION MAY BE REQUIRED LATER THIS AFTERNOON AND EVENING.
IT MAY ALSO BE REQUIRED FRIDAY AFTERNOON AND EVENING. RAINFALL
REPORTS WOULD BE GREATLY APPRECIATED DURING THE PERIOD AS WELL.

DONAVON/REV

In the hours before

Local storm report, Jun 21, 4:59 PM CDT, 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
459 PM CDT THU JUN 21 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0444 PM     FUNNEL CLOUD     WATERLOO                42.49N 92.35W
06/21/2007                   BLACK HAWK         IA   LAW ENFORCEMENT

            FUNNEL CLOUD REPORTED ONE HALF MILE FROM INTERSECTION OF
            FAIRVIEW AND LAFAYETTE IN WATERLOO

0453 PM     HAIL             1 S GRANGER             41.75N 93.82W
06/21/2007  E0.75 INCH       DALLAS             IA   AMATEUR RADIO

            HAIL AND 60 MILE AN HOUR WINDS

&&

31

Local storm report, Jun 21, 5:00 PM CDT, 22 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
500 PM CDT THU JUN 21 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0445 PM     HAIL             7 NE COON RAPIDS        41.94N 94.57W
06/21/2007  E0.88 INCH       GREENE             IA   TRAINED SPOTTER

0453 PM     HAIL             1 S GRANGER             41.75N 93.82W
06/21/2007  E0.75 INCH       DALLAS             IA   AMATEUR RADIO

            HAIL AND 60 MILE AN HOUR WINDS

0455 PM     TSTM WND GST     DE SOTO                 41.53N 94.01W
06/21/2007  E65.00 MPH       DALLAS             IA   TRAINED SPOTTER

            WIND GUST REPORTED IN SOUTH CENTRAL DALLAS COUNTY

&&

MBAKER

Local storm report, Jun 21, 5:07 PM CDT, 15 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
507 PM CDT THU JUN 21 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0445 PM     HAIL             6 SW GREENFIELD         41.24N 94.54W
06/21/2007  E0.88 INCH       ADAIR              IA   TRAINED SPOTTER

&&

BF

Local storm report, Jun 21, 5:13 PM CDT, 9 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
513 PM CDT THU JUN 21 2007

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0458 PM     TORNADO          5 E LUTHER              41.97N 93.72W
06/21/2007                   BOONE              IA   FIRE DEPT/RESCUE

            STORY COUNTY EMERGENCY MANAGER RELAYED FIRE DEPARTMENT
            REPORT TORNADO JUST SOUTH OF NAPIER WHICH IS ALSO ABOUT 5
            MILES EAST OF LUTHER

&&

31

Local storm report, Jun 21, 5:18 PM CDT, 4 minutes before

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Local storm report, Jun 21, 5:18 PM CDT, 4 minutes before

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

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

10.4 hours before the tornado, 186 km from the path. June 21, 2007.

Skew-T log-p

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.

Hodograph

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: 683 J/kg
Mixed-layer CIN: -148 J/kg
Surface CAPE: 0 J/kg
Mixed-layer LCL: 1072 m above ground
0-6 km bulk shear: 30 kt
0-1 km bulk shear: 12 kt
0-1 km storm-relative helicity: 64 m²/s²
0-3 km storm-relative helicity: 23 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2
0-3 km lapse rate: 4.0 K/km

Open this sounding in Storm Lab

Davenport, (KDVN), 00:00Z

1.6 hours after it, 186 km from the path. June 22, 2007.

Skew-T log-p

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.

Hodograph

Mixed-layer CAPE: 1177 J/kg
Mixed-layer CIN: -11 J/kg
Surface CAPE: 2085 J/kg
Mixed-layer LCL: 1514 m above ground
0-6 km bulk shear: 27 kt
0-1 km bulk shear: 1 kt
0-1 km storm-relative helicity: -1 m²/s²
0-3 km storm-relative helicity: 110 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 1.6
0-3 km lapse rate: 7.2 K/km

Open this sounding in Storm Lab

The surface observations

Waterloo (ALO), 6 km from the path, in the two hours either side.

Time (UTC)	Temp (°F)	Dew point (°F)	Wind	Gust (kt)	Pressure (mb)	Weather
00:00 UTC

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

The radar

The Des Moines radar (KDMX), 138 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.

This ground now

The live radar over the track Every 2007 tornado in Iowa Every tornado in Iowa since 1950 Warnings in force in Iowa now The forecast where you are

The other tornadoes of June 21, 2007

7 more were confirmed in the United States that day.

Date	Time	Rating	Where	Path (mi)	Width (yd)	Damage
June 21	3:46 PM EDT	EF1	Seneca, NY	1.5	100	$10,000
June 21	3:51 PM CDT	EF0	Butler, IA	0.1	25
June 21	3:55 PM CDT	EF0	Wright, IA	0.1	30
June 21	4:24 PM CDT	EF0	Butler, IA	0.1	30
June 21	4:58 PM CDT	EF0	Story, IA	0.1	30
June 21	7:05 PM MDT	EF0	Cherry, NE	0.1	20
June 21	7:15 PM MDT	EF1	Cherry, NE	3.0	50	$75,000

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.