July 11, 2011 East Central Iowa Derecho and Severe Wind

Overview

A strong thunderstorm complex moved through east central Iowa and northern Illinois early Monday morning, July 11th.  Damaging winds exceeded 100 mph at times and uprooted large trees, downed power lines, and ripped roofs off of buildings.  Portions of northern Tama, northern Benton, and northwestern Linn County were hardest hit.  National Weather Service storm survey teams assessed damage and estimated wind speeds in the 110 to 130 mph range in these hardest hit areas.  

Details for some of the local communities follow:

Garrison Iowa: straight line wind of 110 to 130 mph produced widespread damage to structures. Many roofs were partially or fully removed and the walls of some buildings collapsed, including the fire station and town library. Nearly every tree was significantly damaged or snapped off . Power outages were widespread. 

Between Garrison and Vinton, 2 pairs of steel electrical transmission towers were bent over.  Several farms received devastating damage, including a house that lost its roof and most exterior walls and another that lost nearly every grain bin and outbuilding.

At Vinton, Iowa: straight line wind in excess of 110 mph caused damage to numerous roof structures and some exterior walls, including a downtown apartment building. Nearly every tree was significantly damaged or snapped off.

See also:

  • Information for farther west  (in the NWS Des Moines service area) including Garwin and Dysart
  • Information for farther east  (in the NWS Chicago service area) including Rockford and Chicago
  • Photos

    If you have photos of damage or additional reports, please share them on our Facebook Page

     Garrison, IA  Fire Department  Garrison, IA Public Library Metal power transmission poles bent over. Flattened corn in foreground. Between Garrison and Vinton.
     
    Devastated farm between Garrison and Vinton Hwy 218 on west side of Vinton. Several large power poles down.  Iowa Braille School.  Vinton, IA
     
    Trees and power lines down on cars and homes in Vinton, IA  Vinton, IA  Public Library lost all trees and some windows.  View down 5th Street in Vinton from intersection of 5th and 2nd.

     Storm Reports

    Local Storm Reports Map - Click on Map for interactive display.

    Map of Storm Reports from July 11, 2011
    National Storm Reports Map

    path of derecho from Nebraska to the East Coast
     

    Radar

    Radar Loop of July 11th
    Radar loop courtesy Iowa Environmental Mesonet.

    The Science Behind the Storm

    This thunderstorm complex fits the description of a bow echo "derecho" which is a widespread, long-lived windstorm that is associated with a band of rapidly moving showers or thunderstorms.  The term bow echo refers to the arched, bow-like structure of the thunderstorm complex seen in the radar reflectivity data above. The same thunderstorm complex that produced widespread wind damage in the Central Plains and Midwest actually persisted all the way to the Mid Atlantic, producing a swath of nearly continuous  wind damage of varying magnitude. 

    The Evolution:  The storm first took shape as a cluster of low end severe storms over southern Nebraska during the late afternoon of July 10. The system continued northeastward and entered western Iowa after midnight, still as a line of marginally severe storms. As the system passed through the northern Des Moines metro area around 3:30am, it interacted with an outflow boundary from the storms to the north and rapidly intensified as it accelerated eastward. Over the next hour and a half the storm plowed eastward through Story, Marshall, and Tama Counties, blasting the area with winds of up to 105 mph, the equivalent of an EF1 tornado. The storm continued to track eastward, intensifying further as it plowed through Benton and Linn Counties with peak winds estimated at 110 to 130 mph.  The storm then began to weaken but remained severe as it continued eastward into northern Illinois and the southern Great Lakes region before dissipating in Maryland mid-afternoon. Thousands of trees were downed in eastern Iowa alone and numerous structures were damaged or destroyed.

    The Environment: Derechos are able to last for several hours, and their gust fronts produce high end damage. In order for these storms to last so long, they need both instability and wind shear. Instability refers to the storm's ability to tap into the warm moist air near the surface as it develops. Meteorologists use the term CAPE (Convective Available Potential Energy) as a way to measure the amount of instability. Wind shear refers to how the wind changes at different heights above ground. Generally, severe weather is likely when the atmosphere has a combination of both high instability and high shear values. In this case, there was plenty of warm moist air at the surface. Temperatures as of 2AM were near 80F across Central Iowa, and dew points were in the mid 70s. This contributed to high CAPE values of near 5000 J/kg. At the same time, the wind shear in the lowest 3000 ft of the atmosphere was near 30 kts, which is quite high. 

    Additional Information


    PRELIMINARY LOCAL STORM REPORT...SUMMARY
    NATIONAL WEATHER SERVICE QUAD CITIES IA IL
    1012 AM CDT MON JUL 11 2011
    
    ..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
    ..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
                ..REMARKS..
    
    0438 AM     TSTM WND GST     BELLE PLAINE            41.90N 92.27W
    07/11/2011  E55.00 MPH       BENTON             IA   EMERGENCY MNGR
    
                ESTIMATED 50 TO 55 MPH WINDS
    
    0449 AM     TSTM WND GST     3 SE KEYSTONE           41.97N 92.15W
    07/11/2011  M75.00 MPH       BENTON             IA   TRAINED SPOTTER
    
    0450 AM     TSTM WND DMG     BELLE PLAINE            41.90N 92.27W
    07/11/2011                   BENTON             IA   TRAINED SPOTTER
    
                LARGE TREES DOWN IN TOWN WITH POWER OUTAGES REPORTED ON
                NORTH SIDE.
    
    0450 AM     TSTM WND GST     BELLE PLAINE            41.90N 92.27W
    07/11/2011  E60.00 MPH       BENTON             IA   TRAINED SPOTTER
    
    0458 AM     TSTM WND GST     VINTON                  42.16N 92.03W
    07/11/2011  E65.00 MPH       BENTON             IA   EMERGENCY MNGR
    
                REPORTED BY BENTON EOC.
    
    0500 AM     TSTM WND GST     VINTON                  42.16N 92.03W
    07/11/2011  M70.00 MPH       BENTON             IA   EMERGENCY MNGR
    
                70+ MPH WINDS BEING SEEN AT THIS TIME.
    
    0501 AM     TSTM WND DMG     2 N VINTON              42.19N 92.03W
    07/11/2011                   BENTON             IA   EMERGENCY MNGR
    
                SEMI BLOWN OFF HIGHWAY 150 JUST NORTH OF TOWN.
    
    0503 AM     TSTM WND DMG     KEYSTONE                42.00N 92.20W
    07/11/2011                   BENTON             IA   TRAINED SPOTTER
    
                NUMEROUS 12 TO 14 INCH TREES DOWN IN TOWN...CROP DAMAGE
                IS ALSO BEING SEEN. TIME ESTIMATED FROM RADAR.
    
    0505 AM     TSTM WND DMG     W VINTON                42.16N 92.03W
    07/11/2011                   BENTON             IA   TRAINED SPOTTER
    
                2X4 FLEW THROUGH EXTERIOR WALL OF HOME...KNOCKING TV OVER
                INSIDE HOME...TIME ESTIMATED FROM RADAR.
    
    0505 AM     TSTM WND GST     1 SSE CEDAR RAPIDS      41.95N 91.66W
    07/11/2011  E60.00 MPH       LINN               IA   TRAINED SPOTTER
    
    0506 AM     TSTM WND GST     CEDAR RAPIDS MUNICIPAL  41.88N 91.72W
    07/11/2011  M52.00 MPH       LINN               IA   ASOS
    
    0509 AM     TSTM WND GST     1 NW MARION             42.05N 91.61W
    07/11/2011  E60.00 MPH       LINN               IA   TRAINED SPOTTER
    
                ESTIMATED 55 TO 60 MPH.
    
    0510 AM     TSTM WND DMG     2 S CENTER POINT        42.16N 91.78W
    07/11/2011                   LINN               IA   TRAINED SPOTTER
    
                3 TREES BLOWN OVER LEWIS ACCESS ROAD BLOCKING ROAD TO
                BRIDGE ACROSS CEDAR RIVER.  TIME ESTIMATED.
    
    0510 AM     TSTM WND DMG     CENTER POINT            42.19N 91.78W
    07/11/2011                   LINN               IA   TRAINED SPOTTER
    
                LARGE NUMBER OF 12 TO 16 INCH TREES DOWN IN
                TOWN...DELAYED REPORT.  TIME ESTIMATED.
    
    0511 AM     TSTM WND GST     1 SSE CEDAR RAPIDS      41.95N 91.66W
    07/11/2011  E80.00 MPH       LINN               IA   TRAINED SPOTTER
    
    0512 AM     TSTM WND GST     VINTON                  42.16N 92.03W
    07/11/2011  M60.00 MPH       BENTON             IA   EMERGENCY MNGR
    
                SINCE 5 AM HAVE HAD SUSTAINED 60 MPH WINDS...REPORTED BY
                COUNTY EOC.
    
    0512 AM     TSTM WND GST     3 E CEDAR RAPIDS        41.97N 91.61W
    07/11/2011  E70.00 MPH       LINN               IA   TRAINED SPOTTER
    
    0514 AM     TSTM WND DMG     URBANA                  42.22N 91.88W
    07/11/2011                   BENTON             IA   TRAINED SPOTTER
    
                INTERSTATE SIGNS BLOWN OVER NEAR SUNSET ST EXIT ON
                I-380...MANY 4 INCH DIAMETER TREES SNAPPED OFF...TIME
                ESTIMATED FROM RADAR.
    
    0515 AM     TSTM WND GST     1 NW SHELLSBURG         42.10N 91.88W
    07/11/2011  E80.00 MPH       BENTON             IA   TRAINED SPOTTER
    
                TIME ESTIMATED FROM RADAR.
    
    0516 AM     TSTM WND DMG     URBANA                  42.22N 91.88W
    07/11/2011                   BENTON             IA   TRAINED SPOTTER
    
                8 SMALL UTILITY SIZE TRAILERS BLOWN OVER ON I-380...LOTS
                OF FLATTENED CROP DAMAGE IN THE AREA SEEN AS WELL...TIME
                ESTIMATED FROM RADAR.
    
    0520 AM     TSTM WND DMG     CENTER POINT            42.19N 91.78W
    07/11/2011                   LINN               IA   TRAINED SPOTTER
    
                LAZY ACRES CAMPGROUND...CAMPER FLIPPED OVER...TIME
                ESTIMATED FROM RADAR.
    
    0521 AM     TSTM WND DMG     SHELLSBURG              42.09N 91.87W
    07/11/2011                   BENTON             IA   EMERGENCY MNGR
    
                METAL BUILDING COMPLETELY DESTROYED WITH NUMEROUS ROOFS
                BLOWN OVER IN TOWN.
    
    0523 AM     TSTM WND GST     TODDVILLE               42.10N 91.72W
    07/11/2011  M72.00 MPH       LINN               IA   EMERGENCY MNGR
    
                TIME ESTIMATED FROM RADAR.
    
    0524 AM     TSTM WND DMG     CENTER POINT            42.19N 91.78W
    07/11/2011                   LINN               IA   FIRE DEPT/RESCUE
    
                SEMI OVERTURNED AT CENTER POINT I-380 TRUCK STOP.
    
    0524 AM     TSTM WND GST     CENTER POINT            42.19N 91.78W
    07/11/2011  E60.00 MPH       LINN               IA   FIRE DEPT/RESCUE
    
                60+ MPH WINDS...RELAYED BY EMERGENCY MANAGER.
    
    0524 AM     TSTM WND GST     PALO                    42.06N 91.80W
    07/11/2011  E70.00 MPH       LINN               IA   FIRE DEPT/RESCUE
    
                TIME ESTIMATED FROM RADAR...RELAYED BY EMERGENCY MANAGER.
    
    
    0525 AM     TSTM WND DMG     TODDVILLE               42.10N 91.72W
    07/11/2011                   LINN               IA   EMERGENCY MNGR
    
                NUMEROUS POWER OUTAGES REPORTED IN TOWN AS WELL AS IN
                ALBURNETT.
    
    0528 AM     TSTM WND DMG     ANAMOSA                 42.11N 91.28W
    07/11/2011                   JONES              IA   EMERGENCY MNGR
    
                COUNTY EMA REPORTS TREES DOWN COUNTYWIDE. OCCURRED
                BETWEEN ABOUT 520 AM AND 610 AM.
    
    0530 AM     TSTM WND DMG     WALKER                  42.29N 91.78W
    07/11/2011                   LINN               IA   FIRE DEPT/RESCUE
    
                NUMEROUS TREES BLOWN OVER WITH SOME CARS DAMAGED.
    
    0530 AM     TSTM WND DMG     PALO                    42.06N 91.80W
    07/11/2011                   LINN               IA   TRAINED SPOTTER
    
                3 FOOT DIAMETER TREE BLOWN DOWN. DELAYED REPORT RELAYED
                BY DES MOINES NWS OFFICE.
    
    0535 AM     TSTM WND GST     MONTICELLO MUNICIPAL AI 42.23N 91.17W
    07/11/2011  M66.00 MPH       JONES              IA   AWOS
    
    0537 AM     TSTM WND DMG     S MANCHESTER            42.49N 91.46W
    07/11/2011                   DELAWARE           IA   EMERGENCY MNGR
    
                WINDOWS BROKEN IN SOME HOMES...WITH SOME POWER OUTAGES
                BEING REPORTED AS WELL.
    
    0550 AM     TSTM WND DMG     4 WNW DUBUQUE           42.52N 90.76W
    07/11/2011                   DUBUQUE            IA   TRAINED SPOTTER
    
                ASBURY AREA. 24 INCH DIAMETER TREE SPLIT IN HALF. ALSO
                1.3 INCHES OF RAIN WITH STORM.
    
    0554 AM     TSTM WND DMG     3 SSW CENTER JUNCTION   42.07N 91.11W
    07/11/2011                   JONES              IA   TRAINED SPOTTER
    
                TOP HALF OF A 12 INCH DIAMETER PINE TREE SNAPPED OFF.
    
    0554 AM     TSTM WND GST     3 SSW CENTER JUNCTION   42.07N 91.11W
    07/11/2011  E65.00 MPH       JONES              IA   TRAINED SPOTTER
    
    0555 AM     TSTM WND GST     DUBUQUE REGIONAL AIRPOR 42.40N 90.72W
    07/11/2011  M60.00 MPH       DUBUQUE            IA   ASOS
    
    0600 AM     TSTM WND GST     CHARLOTTE               41.96N 90.47W
    07/11/2011  M72.00 MPH       CLINTON            IA   TRAINED SPOTTER
    
    0600 AM     TSTM WND DMG     CHARLOTTE               41.96N 90.47W
    07/11/2011                   CLINTON            IA   TRAINED SPOTTER
    
                TWO LARGE TREES BLOWN DOWN.
    
    0602 AM     TSTM WND DMG     4 WNW DUBUQUE           42.52N 90.76W
    07/11/2011                   DUBUQUE            IA   TRAINED SPOTTER
    
                12 INCH DIAMETER TREES DOWN ON PROPERTY ON TOP OF AN
                OUTBUILDING.
    
    0607 AM     TSTM WND GST     DUBUQUE REGIONAL AIRPOR 42.40N 90.72W
    07/11/2011  M64.00 MPH       DUBUQUE            IA   ASOS
    
    0610 AM     TSTM WND GST     DUBUQUE REGIONAL AIRPOR 42.40N 90.72W
    07/11/2011  M74.00 MPH       DUBUQUE            IA   ASOS
    
    0610 AM     TSTM WND GST     3 W BALLTOWN            42.64N 90.93W
    07/11/2011  M67.00 MPH       DUBUQUE            IA   TRAINED SPOTTER
    
                ALSO WIDESPREAD CROP DAMAGE.
    
    0615 AM     TSTM WND GST     1 N LONG GROVE          41.71N 90.58W
    07/11/2011  E60.00 MPH       SCOTT              IA   NWS EMPLOYEE
    
                DAMAGE TO SHINGLES ON HOME.
    
    0615 AM     HEAVY RAIN       WSW QUASQUETON          42.40N 91.76W
    07/11/2011  M1.37 INCH       BUCHANAN           IA   COCORAHS
    
                RAIN FELL BETWEEN 5 AM AND 6 AM THIS MORNING.
    
    0616 AM     TSTM WND GST     DAVENPORT MUNICIPAL AIR 41.62N 90.58W
    07/11/2011  M54.00 MPH       SCOTT              IA   ASOS
    
    0620 AM     TSTM WND DMG     W APPLE RIVER           42.50N 90.10W
    07/11/2011                   JO DAVIESS         IL   TRAINED SPOTTER
    
                SEVERAL LARGE TREES BLOWN DOWN ALONG WITH METAL FLAG
                POLE.
    
    0625 AM     TSTM WND GST     7 NW MOUNT CARROLL      42.17N 90.07W
    07/11/2011  E65.00 MPH       CARROLL            IL   TRAINED SPOTTER
    
    0625 AM     TSTM WND DMG     CLINTON                 41.84N 90.23W
    07/11/2011                   CLINTON            IA   TRAINED SPOTTER
    
                POWER LINES DOWN IN TOWN. TIME ESTIMATED.
    
    0627 AM     TSTM WND DMG     STOCKTON                42.35N 90.01W
    07/11/2011                   JO DAVIESS         IL   BROADCAST MEDIA
    
                STORM WINDOWS BLOWN IN. METAL YARD FURNITURE BLOWN AROUND
                YARD. RELAYED PUBLIC REPORT BY WREX.
    
    0627 AM     TSTM WND GST     4 WSW LORAN             42.22N 89.99W
    07/11/2011  E65.00 MPH       JO DAVIESS         IL   TRAINED SPOTTER
    
    0628 AM     TSTM WND GST     DUBUQUE REGIONAL AIRPOR 42.40N 90.72W
    07/11/2011  M56.00 MPH       DUBUQUE            IA   ASOS
    
    0630 AM     TSTM WND DMG     E ANDREW                42.15N 90.59W
    07/11/2011                   JACKSON            IA   TRAINED SPOTTER
    
                1 INCH DIAMETER LIMBS DOWN IN ANDREW.
    
    0630 AM     TSTM WND DMG     MAQUOKETA               42.07N 90.67W
    07/11/2011                   JACKSON            IA   TRAINED SPOTTER
    
                TREE BRANCHES DOWN BLOCKING STREETS IN MAQUOKETA. TIME
                ESTIMATED. POWER OUTAGE.
    
    0635 AM     TSTM WND GST     1 ESE NORA              42.46N 89.93W
    07/11/2011  E70.00 MPH       JO DAVIESS         IL   TRAINED SPOTTER
    
    0635 AM     TSTM WND DMG     1 ESE NORA              42.46N 89.93W
    07/11/2011                   JO DAVIESS         IL   TRAINED SPOTTER
    
                LARGE TREE BLOWN DOWN.
    
    0650 AM     TSTM WND GST     3 W ROCK FALLS          41.77N 89.74W
    07/11/2011  E60.00 MPH       WHITESIDE          IL   TRAINED SPOTTER
    
                TIME ESTIMATED
    
    0653 AM     TSTM WND GST     ROCK FALLS              41.77N 89.69W
    07/11/2011  E60.00 MPH       WHITESIDE          IL   EMERGENCY MNGR
    
                ESTIMATED 50 TO 60 MPH WINDS...RELAYED BY ROCK FALLS
                ESDA.
    
    0653 AM     TSTM WND GST     STERLING                41.80N 89.69W
    07/11/2011  E70.00 MPH       WHITESIDE          IL   TRAINED SPOTTER
    
    0655 AM     TSTM WND GST     FREEPORT ALBERTUS AIRPO 42.25N 89.58W
    07/11/2011  M57.00 MPH       STEPHENSON         IL   AWOS

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