National Weather Service United States Department of Commerce

Cumulonimbus cloud across Northwest Iowa viewed from the NWS Office

An impressive view of the severe weather producing supercell thunderstorm just before sunset, from the perspective of NWS Sioux Falls.  This storm was about 85 miles to the southeast in extreme northern Buena Vista county at the time.

 

Local storm reports plot

 

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE SIOUX FALLS SD
849 PM CDT WED AUG 13 2008

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

0330 PM     HAIL             4 NW MARSHALL           44.50N 95.84W
08/13/2008  E0.75 INCH       LYON               MN   TRAINED SPOTTER

0355 PM     HAIL             1 W MARSHALL            44.45N 95.81W
08/13/2008  E0.88 INCH       LYON               MN   TRAINED SPOTTER

0355 PM     HAIL             2 SW MARSHALL           44.43N 95.82W
08/13/2008  E0.75 INCH       LYON               MN   TRAINED SPOTTER

0403 PM     HAIL             3 NNE RUSSELL           44.35N 95.92W
08/13/2008  E1.25 INCH       LYON               MN   TRAINED SPOTTER

            HALF DOLLAR SIZED HIAL REPORTED AT CAMDEN STATE PARK.

0403 PM     HAIL             6 NNE ARCO              44.46N 96.11W
08/13/2008  E0.75 INCH       LINCOLN            MN   TRAINED SPOTTER

0405 PM     HAIL             2 SE LAKE BENTON        44.24N 96.26W
08/13/2008  E1.50 INCH       LINCOLN            MN   PUBLIC

0410 PM     HAIL             1 N RUSSELL             44.33N 95.95W
08/13/2008  E1.00 INCH       LYON               MN   TRAINED SPOTTER

            IN ADDITION TO QUARTER SIZED HAIL, 40 TO 50 MPH WIND
            GUSTS ACCOMPANIED THE STORM.

0429 PM     HAIL             1 S BURKE               43.17N 99.29W
08/13/2008  E0.75 INCH       GREGORY            SD   PUBLIC

0430 PM     HAIL             12 NNW MOUNTAIN LAKE    44.10N 95.02W
08/13/2008  E0.75 INCH       COTTONWOOD         MN   PUBLIC

            IN ADDITION TO PENNY SIZED HAIL, 0.65 INCH RAIN FELL
            DURING THE STORM.

0430 PM     HAIL             BALATON                 44.23N 95.87W
08/13/2008  E0.75 INCH       LYON               MN   TRAINED SPOTTER

0445 PM     HAIL             2 SE WOODSTOCK          43.99N 96.06W
08/13/2008  E1.75 INCH       MURRAY             MN   TRAINED SPOTTER

0450 PM     HAIL             12 E PIPESTONE          44.00N 96.07W
08/13/2008  E0.75 INCH       PIPESTONE          MN   TRAINED SPOTTER

0502 PM     HAIL             1 S DALLAS              43.22N 99.52W
08/13/2008  E0.75 INCH       GREGORY            SD   PUBLIC

            IN ADDITION TO PENNY SIZED HAIL, 1.00 INCH OF RAIN FELL
            WITH THIS STORM.

0510 PM     HAIL             1 N EDGERTON            43.89N 96.13W
08/13/2008  E1.00 INCH       PIPESTONE          MN   TRAINED SPOTTER

            IN ADDITION TO QUARTER SIZED HAIL, ROTATION WAS NOTED IN
            THE CLOUDS.

0512 PM     HAIL             EDGERTON                43.87N 96.13W
08/13/2008  E3.00 INCH       PIPESTONE          MN   LAW ENFORCEMENT

            THREE AND A HALF INCH DIAMETER HAIL WAS REPORTED JUST
            WEST OF EDGERTON.

0515 PM     HAIL             2 N EDGERTON            43.90N 96.13W
08/13/2008  E1.75 INCH       PIPESTONE          MN   TRAINED SPOTTER

0525 PM     HAIL             7 S GREGORY             43.13N 99.43W
08/13/2008  E0.75 INCH       GREGORY            SD   PUBLIC

            A LOT OF PEA TO PENNY SIZED HAIL WITH VERY HEAVY RAIN

0540 PM     HAIL             5 SSW OKABENA           43.67N 95.35W
08/13/2008  E0.88 INCH       JACKSON            MN   TRAINED SPOTTER

0553 PM     HAIL             MAGNOLIA                43.64N 96.07W
08/13/2008  E1.00 INCH       ROCK               MN   TRAINED SPOTTER

0600 PM     HAIL             3 NNW ELLSWORTH         43.56N 96.04W
08/13/2008  E0.88 INCH       NOBLES             MN   TRAINED SPOTTER

0608 PM     TSTM WND DMG     2 NE LAKE PARK          43.47N 95.30W
08/13/2008                   DICKINSON          IA   EMERGENCY MNGR

            HALF OF A HOG BARN DESTROYED


0617 PM     TSTM WND GST     LAKE PARK               43.45N 95.32W
08/13/2008  E60.00 MPH       DICKINSON          IA   TRAINED SPOTTER

0617 PM     HAIL             LAKE PARK               43.45N 95.32W
08/13/2008  E1.75 INCH       DICKINSON          IA   TRAINED SPOTTER

0621 PM     HAIL             LAKE PARK               43.45N 95.32W
08/13/2008  E2.00 INCH       DICKINSON          IA   TRAINED SPOTTER

0630 PM     HAIL             3 N GEORGE              43.39N 96.00W
08/13/2008  E0.88 INCH       LYON               IA   TRAINED SPOTTER

0633 PM     HAIL             2 SW WAHPETON           43.35N 95.20W
08/13/2008  E1.00 INCH       DICKINSON          IA   TRAINED SPOTTER

0654 PM     HAIL             6 ENE DICKENS           43.18N 94.93W
08/13/2008  E0.75 INCH       CLAY               IA   TRAINED SPOTTER

0715 PM     HAIL             ROYAL                   43.06N 95.28W
08/13/2008  E1.00 INCH       CLAY               IA   BROADCAST MEDIA

0718 PM     HAIL             3 W WEBB                42.95N 95.07W
08/13/2008  E1.00 INCH       CLAY               IA   BROADCAST MEDIA

0735 PM     HAIL             LINN GROVE              42.89N 95.24W
08/13/2008  E1.75 INCH       BUENA VISTA        IA   BROADCAST MEDIA

0740 PM     HAIL             1 SE LINN GROVE         42.88N 95.23W
08/13/2008  E0.88 INCH       BUENA VISTA        IA   TRAINED SPOTTER

0800 PM     HAIL             STORM LAKE              42.65N 95.20W
08/13/2008  E0.88 INCH       BUENA VISTA        IA   PUBLIC

0806 PM     HAIL             STORM LAKE              42.65N 95.20W
08/13/2008  E1.00 INCH       BUENA VISTA        IA   LAW ENFORCEMENT

0807 PM     HAIL             STORM LAKE              42.65N 95.20W
08/13/2008  E0.88 INCH       BUENA VISTA        IA   TRAINED SPOTTER

0815 PM     HAIL             6 ESE STORM LAKE        42.60N 95.10W
08/13/2008  E0.75 INCH       BUENA VISTA        IA   TRAINED SPOTTER

            ONE TO TWO INCHES DEEP


Below are radar images corresponding to the damage to the hog barn northeast of Lake Park, highlighted in the storm report listing above. The first is a radar reflectivity image at 608 pm CDT.  Note the distinct hook echo in the image.  The second image is the corresponding storm relative motion image.  While this represents a feature at approximately 8700 feet above ground level, it is still indicative of the low level mesocyclonic rotation in the storm. 

Radar reflectivity image at 608 pm featuring a distinct hook echo


Storm relative velocity image at 608 pm CDT