Alert archive / Iowa / Severe Thunderstorm Warnings in 2008

Severe Thunderstorm Warning 237, NWS Quad Cities, IA

July 21, 20087 counties in Iowa; Mercer County, Rock Island County, Illinois

NWS Quad Cities, IA issued this severe thunderstorm warning at Jul 21, 2008, 5:06 AM CDT for 7 counties in Iowa; Mercer County, Rock Island County, Illinois. It was in force for 54 min. 21 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 21, 2008, 5:06 AM CDT (10:06 UTC)
Expired: Jul 21, 2008, 6:00 AM CDT
In force: 54 min
Issued by: NWS Quad Cities, IA
Area: Storm-based polygon

Counties Cedar County, IA, Clinton County, IA, Johnson County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Washington County, IA, Mercer County, IL, Rock Island County, IL

The radar

The Quad Cities radar (KDVN), 53 km from the middle of the area, began a volume at 10:09 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Jul 21, 5:15 AM CDT	TSTM WND GST 50	N Riverside, IA
Jul 21, 5:15 AM CDT	TSTM WND GST 80	10 S Iowa City, IA
Jul 21, 5:15 AM CDT	HAIL 0.88	10 S Iowa City, IA
Jul 21, 5:16 AM CDT	TSTM WND GST 70	Lone Tree, IA
Jul 21, 5:21 AM CDT	HAIL 0.75	1 N Muscatine, IA	PEA TO PENNY SIZE HAIL
Jul 21, 5:28 AM CDT	TSTM WND DMG	Lone Tree, IA	POWER IS OUT ACROSS CITY...NUMEROUS LARGE TREE LIMBS DOWN...SOME UP TO 1 FOOT IN DIAMETER.
Jul 21, 5:33 AM CDT	TSTM WND GST 63	Muscatine, IA
Jul 21, 5:35 AM CDT	TSTM WND GST 70	3 Ene Muscatine, IA
Jul 21, 5:42 AM CDT	TSTM WND GST 55	Wilton, IA
Jul 21, 5:45 AM CDT	TSTM WND DMG	4 E Muscatine, IL	SHED IN DITCH...HIGHWAY SIGNS BLOWN OVER...TREES DOWN ON HWY 61
Jul 21, 5:45 AM CDT	TSTM WND DMG	Muscatine, IA	8 INCH DIAMETER BRANCHES DOWN...POWER OUT
Jul 21, 5:45 AM CDT	TSTM WND GST 60	Muscatine, IA
Jul 21, 5:46 AM CDT	TSTM WND DMG	Nw Muscatine, IA	TREES DOWN
Jul 21, 5:46 AM CDT	TSTM WND GST 61	Muscatine, IA
Jul 21, 5:48 AM CDT	TSTM WND DMG	Illinois City, IL	EVERY THING HAS BEEN BLOWN OFF THE PORCH
Jul 21, 5:54 AM CDT	TSTM WND GST 59	2 N Muscatine, IA	OBSERVER ALSO REPORTS SEVERAL LARGE TREES DOWN AROUND THE AREA WITH THE LARGEST AT 3 FOOT IN DIAMETER. ALSO REPORTED 1.39 INCH PRECIPITATION IN ABOUT 30 MINUTES PRODUCING MINOR STRETT FLOODING IN THE AREA.
Jul 21, 5:55 AM CDT	TSTM WND DMG	Montpelier, IA	BIG BRANCHES DOWN...SIDING BLOWN OFF THE HOUSE AND POWER OUT
Jul 21, 6:00 AM CDT	TSTM WND DMG	Rock Island, IL	TREES AND BRANCHES DOWN ON 26TH STREET
Jul 21, 6:01 AM CDT	TSTM WND GST 59	5 W Davenport Municipal, IA	DELAYED REPORT. IDOT RWIS AT JCT OF I-80 AND I-280.
Jul 21, 6:04 AM CDT	TSTM WND GST 39	Davenport Municipal Air, IA
Jul 21, 6:10 AM CDT	TSTM WND GST 81	Moline Quad-City Airpor, IL

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched 15 storm reports to this severe thunderstorm warning; the first came 9 minutes after it went out.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 20, 11:25 PM CDT	Severe Thunderstorm Watch	SPC	8 hr
Jul 21, 4:21 AM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 10.1 hours before the alert went out and 60 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

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.

Mixed-layer CAPE: 1891 J/kg
Mixed-layer CIN: -56 J/kg
Mixed-layer LCL: 1142 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 29 m²/s²
0-3 km storm-relative helicity: 100 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.4

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WUUS53 KDVN 211007
SVRDVN
IAC031-045-103-115-139-163-183-ILC131-161-211100-
/O.NEW.KDVN.SV.W.0237.080721T1006Z-080721T1100Z/

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
506 AM CDT MON JUL 21 2008

THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CEDAR COUNTY IN EAST CENTRAL IOWA...
  SOUTHWESTERN CLINTON COUNTY IN EAST CENTRAL IOWA...
  EASTERN JOHNSON COUNTY IN EAST CENTRAL IOWA...
  MUSCATINE COUNTY IN EAST CENTRAL IOWA...
  SCOTT COUNTY IN EAST CENTRAL IOWA...
  MERCER COUNTY IN NORTHWEST ILLINOIS...
  ROCK ISLAND COUNTY IN NORTHWEST ILLINOIS...  
  LOUISA COUNTY IN SOUTHEAST IOWA...
  EASTERN WASHINGTON COUNTY IN SOUTHEAST IOWA...

* UNTIL 600 AM CDT.

* AT 504 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DESTRUCTIVE WINDS
  IN EXCESS OF 70 MPH.  THESE STORMS WERE LOCATED APPROXIMATELY ALONG
  A LINE EXTENDING FROM 8 MILES NORTHWEST OF MECHANICSVILLE TO 15
  MILES SOUTHWEST OF MORNING SUN...OR ALONG A LINE EXTENDING FROM 9
  MILES SOUTHWEST OF ANAMOSA TO MOUNT PLEASANT...AND MOVING EAST AT
  60 MPH.

* SEVERE THUNDERSTORMS WILL BE NEAR...
  WEST LIBERTY AROUND 515 AM CDT...
  TIPTON...STANWOOD...MORNING SUN AND LETTS AROUND 520 AM CDT...
  WAPELLO...GRANDVIEW...FRUITLAND AND CLARENCE AROUND 525 AM CDT...
  WILTON AROUND 530 AM CDT...

THIS INCLUDES INTERSTATE 80 IN IOWA BETWEEN MILE MARKERS 246 AND 301.

THIS INCLUDES INTERSTATE 74 IN IOWA BETWEEN MILE MARKERS 1 AND 5.

THIS INCLUDES INTERSTATE 74 IN ILLINOIS BETWEEN MILE MARKERS 1 AND 5.

THIS INCLUDES INTERSTATE 280 BETWEEN MILE MARKERS 1 AND 18.

THIS IS A DANGEROUS STORM. MOVE IMMEDIATELY INDOORS AND STAY AWAY
FROM WINDOWS.

THIS STORM HAS ALREADY PRODUCED WIND DAMAGE AND/OR LARGE HAIL...AND
IT REMAINS A THREAT.

THIS STORM IS ALSO PRODUCING HEAVY RAIN AND URBAN AND SMALL STREAM
FLOODING.

LAT...LON 4185 9136 4193 9137 4188 9044 4108 9050
      4108 9137 4116 9137 4117 9168 4185 9148
TIME...MOT...LOC 1006Z 270DEG 39KT 4199 9133 4099 9147

$$

ERVIN

1 follow-up statement

000 
WWUS53 KDVN 211101
SVSDVN

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
601 AM CDT MON JUL 21 2008

IAC031-045-103-115-139-163-183-ILC131-161-211111-
/O.EXP.KDVN.SV.W.0237.000000T0000Z-080721T1100Z/
CLINTON IA-CEDAR IA-JOHNSON IA-SCOTT IA-MUSCATINE IA-WASHINGTON IA-
LOUISA IA-ROCK ISLAND IL-MERCER IL-
601 AM CDT MON JUL 21 2008

...THE SEVERE THUNDERSTORM WARNING FOR MERCER...SOUTHWESTERN ROCK
ISLAND...LOUISA...EASTERN WASHINGTON...MUSCATINE...SCOTT...EASTERN
JOHNSON...CEDAR AND SOUTHWESTERN CLINTON COUNTIES EXPIRES AT 600 AM
CDT...

THE THUNDERSTORM THAT WAS CAPABLE OF PRODUCING SEVERE WEATHER HAS
MOVED OUT OF THE WARNED AREA. THEREFORE THE SEVERE THUNDERSTORM
WARNING HAS BEEN ALLOWED TO EXPIRE.

A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT FOR SCOTT COUNTY AND 
ROCK ISLAND COUNTY...INCLUDING THE QUAD CITIES.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 700 AM CDT MONDAY
MORNING FOR NORTHEASTERN IOWA. A SEVERE THUNDERSTORM WATCH ALSO
REMAINS IN EFFECT UNTIL NOON CDT MONDAY FOR SOUTHEASTERN IOWA AND
NORTHWESTERN ILLINOIS AND NORTHEAST MISSOURI.

LAT...LON 4185 9136 4193 9137 4188 9044 4108 9050
      4108 9137 4116 9137 4117 9168 4185 9148
TIME...MOT...LOC 1006Z 270DEG 39KT 4199 9133 4099 9147

$$

ERVIN

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Quad Cities, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at Jul 21, 2:30 AM CDT, 2 hours 36 minutes earlier.

Area forecast discussion, Jul 21, 2:30 AM CDT, 2 hours 36 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 AM CDT MON JUL 21 2008

.DISCUSSION...
COMPLICATED SET UP OCCURRING THIS MORNING AS WE HAVE BOTH A SEVERE
FORWARD PROPAGATING MCS OVER IOWA...AND STRONG TO SEVERE CELLS
FORMING OUT AHEAD OF IT.  THE 850MB CONVERGENCE BOUNDARY AHEAD OF
THE MCS IS GRADUALLY FILLING IN WITH STRONG STORMS...SOME ARE
HEADING SOUTHEAST...WHILE OTHER ARE MOVING DUE EAST.  THIS ACTIVITY
WILL LIKELY MERGE WITH THE MCS COMING FROM THE WEST.  THE MAIN
QUESTION IS HOW FAR NORTH THE AREAL COVERAGE WILL BE WITH THE MCS.
ONCE THE CONVECTION ENTERS EASTERN IOWA AND ILLINOIS...IT THE MCS
SHOULD MOVE SOUTHEAST...MORE SO WITH TIME.  HOWEVER...PORTIONS OF
THE MCS IN CENTRAL IOWA ARE ALREADY DOING SO...WHILE OTHER MAJOR
PORTION ARE HEADING DUE EAST.  THE HEAVIEST RAINS SEEM CONFIDENT TO
OCCUR ALONG AND 50 MILES EITHER SIDE OF A LINE FROM AMES IOWA...TO
WAPELLO...TO GALESBURG.  HOWEVER...DESPITE LESSER STORM TOTALS
FARTHER NORTH...MUCH LOWER FFG VALUES WILL WARRANT KEEPING AND
EXTENDING THE FLASH FLOOD WATCH TIL MID MORNING. UP ALONG HIGHWAY
20...A TOUGH CALL IS IN PLACE...WITH MUCH OF THE MCS LIKELY TO ONLY
BRUSH THIS AREA...BUT QUITE LOW FFG THRESHOLDS.  WE WILL WAIT UNTIL
AROUND 300 AM TO MAKE THIS CALL...BUT WILL LIKELY CANCEL BOTH THE
SEVERE THUNDERSTORM AND FLASH FLOOD WATCHES.

TODAY...CATEGORICAL POPS WILL BE USED TO WALK OUT THE MCS...AND
HEAVY RAIN THREAT. CLOUDS WILL LIKELY HOLD DOWN TEMPS TODAY...AND
WILL MAINLY GO LOWER 80S...EXCEPT FOR MID 80S IN THE FAR SOUTH WHERE
SOME AIRMASS RECOVERY IS LIKELY. THE BOUNDARY WILL LIKELY LAY ACROSS
NORTHERN MO THIS AFTERNOON AND TONIGHT. ONCE AGAIN...THE SFC BASED
CONVECTION MAY BE CAPPED OFF...ALLOWING THE MAIN STORMS TO DEVELOP
ROUGHLY 75 TO 100 MILES FARTHER NORTH.  WILL GO WITH CHANCE TO
LIKELY POPS TONIGHT IN THE SOUTH HALF...BUT DAYSHIFT MAY NEED TO
EITHER REMOVE OR UP POPS BASED ON THE OUTFLOW BOUNDARY POSITION
LATER TODAY.

LITTLE CHANGES MADE BEYOND TONIGHT...OTHER THAN ADDING SOME LOW POPS
FOR TUESDAY...WITH AN UNSTABLE ATMOSPHERE IN THE NORTH WITH CYCLONIC
FLOW...AND POTENTIAL FOR ISOLATED ACTIVITY IN THE SOUTH...SOME
SCATTERED SHOWERS AND POSSIBLY THUNDER MAY OCCUR.
...ERVIN...

&&

.AVIATION...
MCS MOVING THROUGH WESTERN IOWA TO AFFECT THE AREA AROUND DAWN AND
INTO THE MORNING HOURS. HIGH IMPACTS EXPECTED AT KCID/KMLI/KBRL WITH
CIGS OF AT LEAST 2 KFT AND VSBYS AOB 2SM WITH TSRA. KDBQ WILL SEE
SOME IMPACTS WITH VSBYS 3-5SM AND POSSIBLY CIGS AROUND 3 KFT.
BOUNDARIES LEFT OVER FROM MCS TO PROVIDE THE FOCUS FOR REDEVELOPMENT
IN THE AFTERNOON/OVERNIGHT TIME PERIOD. WILL HAVE TO WATCH EVOLUTION
OF CURRENT MCS OVER THE NEXT SEVERAL HRS TO GET A BETTER IDEA ON
DEVELOPMENT THIS AFTERNOON/TONIGHT.        ...08...

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...FLASH FLOOD WATCH UNTIL 9 AM CDT THIS MORNING FOR BENTON-
BUCHANAN-CEDAR-CLINTON-IOWA-JOHNSON-JONES-KEOKUK-LINN-
LOUISA-MUSCATINE-SCOTT-WASHINGTON.

IL...FLASH FLOOD WATCH UNTIL 9 AM CDT THIS MORNING FOR MERCER-ROCK
     ISLAND-WHITESIDE.
MO...NONE.

&&

ERVIN/08

In the hours before

Special weather statement, Jul 21, 1:42 AM CDT, 3 hours 24 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
142 AM CDT MON JUL 21 2008

IAZ076-077-210845-
KEOKUK-WASHINGTON-
INCLUDING THE CITIES OF...SIGOURNEY...WASHINGTON
142 AM CDT MON JUL 21 2008

...STRONG THUNDERSTORMS WITH HEAVY RAIN...

THUNDERSTORMS WITH HEAVY RAIN...AND POSSIBLY PEA SIZED HAIL...WILL
CONTINUE TO MOVE ACROSS KEOKUK AND INTO WASHINGTON COUNTIES
THROUGH 4 AM. RAINFALL RATES OF UP TO 1 INCH PER HOUR IS POSSIBLE
WHICH MAY CAUSE PONDING OF WATER ON ROADS.

Special weather statement, Jul 21, 2:51 AM CDT, 2 hours 15 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
251 AM CDT MON JUL 21 2008

IAZ087>089-211000-
JEFFERSON-HENRY IA-DES MOINES-
INCLUDING THE CITIES OF...FAIRFIELD...MOUNT PLEASANT...BURLINGTON
251 AM CDT MON JUL 21 2008

...STRONG THUNDERSTORMS WITH HEAVY RAIN...

THUNDERSTORMS WITH HEAVY RAIN...AND POSSIBLY PEA SIZED HAIL...WILL
CONTINUE TO MOVE ACROSS JEFFERSON...HENRY...AND DES MOINES
COUNTIES THROUGH SUNRISE. RAINFALL RATES OF UP TO 1 INCH PER HOUR
IS POSSIBLE WHICH MAY CAUSE PONDING OF WATER ON ROADS.

Local storm report, Jul 21, 4:00 AM CDT, 1 hour 6 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
400 AM CDT MON JUL 21 2008

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

0357 AM     HAIL             1 NW FAIRFIELD          41.02N 91.98W
07/21/2008  E0.88 INCH       JEFFERSON          IA   TRAINED SPOTTER

&&

15

Local storm report, Jul 21, 4:46 AM CDT, 20 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
446 AM CDT MON JUL 21 2008

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

0440 AM     TSTM WND GST     PRAIRIE CITY            40.62N 90.46W
07/21/2008  E65 MPH          MCDONOUGH          IL   FIRE DEPT/RESCUE

            ESTIMATED 60 TO 70 MPH WINDS. 7 TO 8 INCH DIAMETER
            BRANCHES DOWN.

&&

Local storm report, Jul 21, 4:52 AM CDT, 14 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
452 AM CDT MON JUL 21 2008

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

0444 AM     TSTM WND GST     5 W SIGOURNEY           41.34N 92.31W
07/21/2008  M66 MPH          KEOKUK             IA   MESONET

&&

15

Local storm report, Jul 21, 5:05 AM CDT, 1 minute before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
505 AM CDT MON JUL 21 2008

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

0455 AM     TSTM WND GST     W NORWAY                41.90N 91.93W
07/21/2008  M60 MPH          BENTON             IA   TRAINED SPOTTER

            SUSTAINED WIND 40 TO 45 MPH

&&

15

The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 8:10 PM CDT	River Flood Warning	DVN	Cedar, Louisa, Muscatine	56 hr
Jul 21, 3:49 AM CDT	Severe Thunderstorm Warning	DVN	Henry, Jefferson, Van Buren	41 min
Jul 21, 4:26 AM CDT	Severe Thunderstorm Warning	DVN	Benton, Iowa, Johnson, Keokuk, Linn, Washington	64 min
Jul 21, 4:53 AM CDT	Severe Thunderstorm Warning	DVN	Henry, Jefferson, Van Buren	67 min
Jul 21, 5:46 AM CDT	Severe Thunderstorm Warning	DVN	Des Moines, Scott	59 min
Jul 21, 6:25 AM CDT	Severe Thunderstorm Warning	DVN	Bureau, Putnam, Whiteside	65 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2008 Severe Thunderstorm Warnings in Illinois, 2008 Every severe thunderstorm warning in 2008

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.