Menno wind damage and tornado

Around 7:40 pm CDT, a high precipitation supercell near Menno, South Dakota produced damaging winds in the town of Menno and a tornado which moved north and east of Menno.  Winds were reported to be 70 to 80 mph in Menno with numerous trees uprooted, several windows blown out, and a few sheds damaged.  Several road signs were also reported to be blown down by the damaging winds.  Based upon witness reports, all the damage in Menno appears to be done by straight line winds.  No damage has been reported with the tornado at this time.  However, based on numerous spotter reports, the tornado was on the ground for at least 4 minutes from 7:37 pm - 7:41 pm CDT.  The tornado touched down approximately 3 miles north of Menno.

Below is a brief examination of the radar reflectivity and storm relative velocity as the storm approached Menno.  A definition and example of storm relative velocity from radar can be found at http://okfirst.mesonet.org/train/materials/radar/srm1.gif

Reflectivity at 7:26 pm CDT 16 June 2009

Storm relative velocity from 16 June 2009

At 7:26 pm CDT, the  supercell was located approximately 10 miles northwest of Menno.  This storm had produced some brief tornadoes near Dimock earlier in the evening (see below).   A hail core was located over north-central Hutchinson County and produced golf ball size hail in Clayton.    At the same time, a inflow notch can be seen on the southeast flank of the storm.  Strong winds were bringing warm and humid air into the storm.  At the same time rain and small hail that were associated with a rear flank downdraft can be see to the west of the inflow notch.

Reflectivity image from 7:31 pm CDT 16 June 2009

Storm reflectivity image from 7:31 pm CDT 16 June 2009

At 7:31 pm CDT, the  supercell was  approximately 7 miles northwest of Menno. The hail core is still evident between Clayton and Menno.  In addition, the reflectivity has increased northwest of Menno indicating that more hail may be getting into the rear flank downdraft.  Both the inflow and rear flank down draft are evident on the storm relative velocity image.  Of greater importance a weak circulation can now be seen developing at the end of the inflow notch. 

 

Reflectivity image from 7:40 pm CDT 16 June 2009

Storm relative velocity image from 7:40 pm CDT 16 June 2009

Just 9 minutes later, at 7:40 pm CDT, the circulation has increased significantly as it reaches Menno.  A hail core remains evident north of Menno with a small hail core with the rear flank downdraft over Menno.  Lower reflectivity can be seen northwest of Menno.  It is likely the center of the updraft was just north of where the tornado was reported 3 miles north of Menno.  The fact that high reflectivity surrounds the updraft indicates that the mesocyclone is likely being cutoff and the circulation is going to begin to weaken.  This is typical of high precipitation supercells.

A strong circulation surrounds the tornadic circulation.  In the storm relative velocity image, strong inbounds are located over Menno indicating a westerly component of the wind from the rear flank downdraft.  Eye witnesses reported that winds in the Menno area were actually from the northwest which means the radar was not even sampling the total wind velocity.  While the radar showed winds near Menno around 55 mph, wind estimates by witnesses as well as storm damage indicate actual wind speeds were 70 to 80 mph.  To the north, the warm inflow is evident by the strong outbound winds indicate on radar north of Menno.

As the storm moved southeast, other damaging wind reports were received as well the report of another tornado in Yankton, Clay and Union counties.

 

Severe Weather Reports 16 June 2009

Severe weather reports from June 16, 2009

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1046 PM CDT TUE JUN 16 2009

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

0412 PM     HAIL             15 SSW WOLSEY           44.21N 98.59W
06/16/2009  E0.88 INCH       BEADLE             SD   PUBLIC

0425 PM     HAIL             13 WNW WESSINGTON SPRIN 44.18N 98.79W
06/16/2009  E2.00 INCH       JERAULD            SD   PUBLIC

0425 PM     HAIL             8 NW WESSINGTON SPRINGS 44.16N 98.69W
06/16/2009  E3.00 INCH       JERAULD            SD   PUBLIC

            HAIL WAS INCREASING IN SIZE

0442 PM     HAIL             11 NW WESSINGTON SPRING 44.18N 98.75W
06/16/2009  E1.75 INCH       JERAULD            SD   PUBLIC

            IN ADDITION TO THE GOLFBALL SIZE HAIL, WINDS WERE GUSTING
            TO 50-60 MPH.

0455 PM     HAIL             6 NW WESSINGTON SPRINGS 44.14N 98.65W
06/16/2009  E0.75 INCH       JERAULD            SD   PUBLIC

0500 PM     HAIL             3 W MOUNT VERNON        43.71N 98.32W
06/16/2009  E0.88 INCH       DAVISON            SD   LAW ENFORCEMENT

            IN ADDITION TO NICKEL SIZE HAIL, HEAVY RAIN WAS FALLING
            WEST OF MOUNT VERNON ON THE DAVISON/AURORA COUNTY LINE.

0510 PM     HAIL             WESSINGTON SPRINGS      44.08N 98.57W
06/16/2009  E1.50 INCH       JERAULD            SD   TRAINED SPOTTER

            IN ADDITION TO WALNUT SIZE HAIL, 1.21 INCH OF RAIN FELL
            WITH THIS STORM.

0510 PM     HAIL             4 W LANE                44.07N 98.50W
06/16/2009  E1.00 INCH       JERAULD            SD   PUBLIC

            IN ADDITION TO THE QUARTER SIZE HAIL, WINDS WERE GUSTING
            TO 40-50 MPH.

0524 PM     HAIL             3 S MOUNT VERNON        43.67N 98.25W
06/16/2009  E1.75 INCH       DAVISON            SD   LAW ENFORCEMENT

0530 PM     HAIL             MOUNT VERNON            43.71N 98.26W
06/16/2009  E1.75 INCH       DAVISON            SD   UNKNOWN

0531 PM     TORNADO          6 S MOUNT VERNON        43.63N 98.25W
06/16/2009                   DAVISON            SD   TRAINED SPOTTER

0535 PM     HAIL             5 SSW LANE              44.00N 98.45W
06/16/2009  E1.00 INCH       JERAULD            SD   PUBLIC

0536 PM     HAIL             4 S MOUNT VERNON        43.66N 98.25W
06/16/2009  E1.75 INCH       DAVISON            SD   PUBLIC

0540 PM     HAIL             6 SSW MITCHELL          43.66N 98.08W
06/16/2009  E0.88 INCH       DAVISON            SD   TRAINED SPOTTER

            IN ADDITION TO NICKEL SIZE HAIL, A WALL CLOUD WAS SITED 6
            MILES SSW OF MITCHELL.

0611 PM     HAIL             ETHAN                   43.55N 97.98W
06/16/2009  E1.00 INCH       DAVISON            SD   TRAINED SPOTTER

0636 PM     TORNADO          DIMOCK                  43.48N 97.99W
06/16/2009                   HUTCHINSON         SD   TRAINED SPOTTER

0645 PM     HAIL             6 WNW TAUNTON           44.62N 96.17W
06/16/2009  E1.00 INCH       LINCOLN            MN   TRAINED SPOTTER

0650 PM     TORNADO          6 E DIMOCK              43.47N 97.87W
06/16/2009                   HUTCHINSON         SD   TRAINED SPOTTER

0720 PM     TORNADO          4 NW OLIVET             43.29N 97.73W
06/16/2009                   HUTCHINSON         SD   EMERGENCY MNGR

0726 PM     HAIL             CLAYTON                 43.44N 97.66W
06/16/2009  E1.75 INCH       HUTCHINSON         SD   LAW ENFORCEMENT

0737 PM     TORNADO          3 N MENNO               43.28N 97.58W
06/16/2009                   HUTCHINSON         SD   TRAINED SPOTTER

0740 PM     TSTM WND DMG     MENNO                   43.24N 97.58W
06/16/2009                   HUTCHINSON         SD   STORM CHASER

            LOTS OF TREES UPROOTED, PAINT PEELED OFF SHEDS, AND LOTS
            OF WINDOWS BLOWN OUT. WINDS ESTIMATED AT 70 TO 80 MPH.

0740 PM     TORNADO          2 N MENNO               43.27N 97.58W
06/16/2009                   HUTCHINSON         SD   TRAINED SPOTTER

            CONTINUED TRACK OF TORNADO AT 737 PM.

0740 PM     HAIL             MENNO                   43.24N 97.58W
06/16/2009  M1.00 INCH       HUTCHINSON         SD   STORM CHASER

0741 PM     TORNADO          1 N MENNO               43.25N 97.58W
06/16/2009                   HUTCHINSON         SD   TRAINED SPOTTER

            CONTINUED TRACK OF MENNO TORNADO.

0750 PM     HAIL             1 NW CURRENT LAKE       44.15N 95.96W
06/16/2009  E1.00 INCH       MURRAY             MN   PUBLIC

            IN ADDITION TO QUARTER SIZE HAIL, 1.50 INCH OF RAIN FELL
            WITH THIS STORM.

0800 PM     HAIL             6 SSE MENNO             43.15N 97.55W
06/16/2009  E0.75 INCH       YANKTON            SD   TRAINED SPOTTER

            IN ADDITION TO PENNY SIZE HAIL, 1 TO 2 INCHES OF RAIN
            FELL FROM THIS STORM.

0828 PM     TORNADO          1 NW MISSION HILL       42.93N 97.29W
06/16/2009                   YANKTON            SD   STORM CHASER

0831 PM     TSTM WND GST     1 SE IRENE              43.07N 97.14W
06/16/2009  M60.00 MPH       CLAY               SD   EMERGENCY MNGR

            IN ADDITION TO 60 MPH WIND GUSTS, NICKEL SIZE HAIL WAS
            REPORTED.

0850 PM     HAIL             3 NW SLAYTON            44.02N 95.80W
06/16/2009  E1.75 INCH       MURRAY             MN   PUBLIC

            PLUS 60 MPH WINDS

0902 PM     HAIL             2 N UTICA               43.01N 97.49W
06/16/2009  E1.00 INCH       YANKTON            SD   TRAINED SPOTTER

            IN ADDITION TO QUARTER SIZE HAIL, WINDS WERE GUSTING TO
            40-60 MPH.

0930 PM     TSTM WND GST     7 N VERMILLION          42.88N 96.95W
06/16/2009  E60.00 MPH       CLAY               SD   PUBLIC

0935 PM     TSTM WND GST     1 NNW VERMILLION        42.80N 96.93W
06/16/2009  E65.00 MPH       CLAY               SD   TRAINED SPOTTER

            IN ADDITION TO ESTIMATED 65 MPH WIND GUSTS, CONSTRUCTION
            SIGNS WERE BLOWN OVER ON THE EAST SIDE OF VERMILLION.

0937 PM     HAIL             1 NNW VERMILLION        42.80N 96.93W
06/16/2009  E0.75 INCH       CLAY               SD   TRAINED SPOTTER

0940 PM     TSTM WND GST     VERMILLION              42.78N 96.93W
06/16/2009  E60.00 MPH       CLAY               SD   EMERGENCY MNGR

0949 PM     TSTM WND GST     6 E VERMILLION          42.79N 96.81W
06/16/2009  E65.00 MPH       UNION              SD   TRAINED SPOTTER


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