National Weather Service meteorologists travelled through Dallas and far western Polk counties in Central Iowa today, surveying damage from Sunday's (June 7, 2009) thunderstorms. The following is the official Public Information Statement containing the results of the survey, followed by a map of the damage.
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
342 PM CDT MON JUN 8 2009
...FINAL DAMAGE SURVEY RESULTS FOR DALLAS COUNTY...
...BRIEF PATH OF TORNADIC DAMAGE SOUTH OF DALLAS CENTER...
THE FOLLOWING IS A FINAL ASSESSMENT FOR THE DAMAGE THAT OCCURRED OVER
DALLAS COUNTY ON JUNE 7 2009.
* EVENT DATE: JUNE 7 2009
* ESTIMATED START TIME: 633 PM
* EVENT TYPE: (EF0) TORNADO
* EVENT LOCATION: 3 MILES SOUTH OF DALLAS CENTER TO 3 MILES SOUTH
SOUTHEAST OF DALLAS CENTER
(41.64N -93.96W TO 41.64N -93.93W)
* PEAK WIND: 75 MPH
* AVERAGE PATH WIDTH: 100 YARDS
* PATH LENGTH: 1.5 MILES
* INJURIES: 0
* FATALITIES: 0
* DISCUSSION/DAMAGE: A PATH OF STRAIGHT LINE WIND DAMAGE BEGAN ON
THE SOUTHWEST CORNER OF ADEL AND PROGRESSED EAST NORTHEAST
THROUGH THE SOUTHERN AND CENTRAL PORTION OF CITY. DAMAGE
CONSISTED OF MAINLY TREE DAMAGE WITH LITTLE STRUCTURAL
DAMAGE...WITH THE EXCEPTION WHERE A FEW TREES AND BRANCHES FELL
ON HOUSES. THE WINDS CONTINUED TO PRODUCE TREE DAMAGE ACROSS
HILLCREST GOLF COURSE WITH A MORE INTENSE AREA OF WIND DAMAGE
LOCATED JUST EAST OF THE GOLF COURSE ALONG PROSPECT AVENUE WHERE
SEVERAL LARGE TREES WERE BLOWN DOWN.
DAMAGE FROM THE WEAK EF0 TORNADO WAS FIRST OBSERVED WITH A 10
YARD WIDE PATH OF DAMAGE THROUGH A CORN FIELD NEAR THE
INTERSECTION OF R AVENUE AND 278TH ST. THE WEAK PATH CONTINUED
1.5 MILES TO THE EAST WITH THE MOST INTENSE DAMAGE LOCATED ALONG
270 ST. A 30 YARD CONVERGENT PATH OF SEVERE TREE DAMAGE THROUGH
THIS RESIDENCE AND ENDED SHORTLY TO THE EAST. FALLEN TREES
DAMAGED A GARAGE AND VEHICLES AT THIS RESIDENCE. THE MESOCYCLONE
WEAKENED AFTER THIS POINT.
A NEW AREA OF ROTATION DEVELOPED NEAR GRIMES AND BEGAN TO
PRODUCE STRAIGHT LINE WIND DAMAGE TO TREES IN NORTHWEST SECTIONS
OF GRIMES. THE PRIMARY AREA OF STRAIGHT LINE TREE DAMAGE WAS
LOCATED OVER THE NORTH HALF OF GRIMES. VERY MINOR STRAIGHT LINE
WIND TREE DAMAGE OCCURRED EAST OF HIGHWAY 141 EAST OF THE GRIMES
AREA AND THROUGH NORTHERN JOHNSTON. OTHER PORTIONS OF JOHNSTON
AND THE DES MOINES AREA WERE NOT SURVEYED FROM THE GROUND.
IN ALL CASES...THE AREAS OF STRAIGHT LINE WIND DAMAGE WERE
CORRELATED AND CONCENTRATED IN NARROW PATHS ALONG THE SOUTHERN
PERIPHERY OF THE MESOCYCLONES AS DETECTED ON RADAR.
THANKS TO DALLAS COUNTY EMERGENCY MANAGEMENT FOR DETAILED DAMAGE LOCATION INFORMATION USED IN THIS SURVEY.
FOR REFERENCE...THE ENHANCED FUJITA TORNADO SCALE CLASSIFIES
TORNADOES INTO THE FOLLOWING CATEGORIES:
EF0...WIND SPEEDS 65 TO 85 MPH.
EF1...WIND SPEEDS 86 TO 110 MPH.
EF2...WIND SPEEDS 111 TO 135 MPH.
EF3...WIND SPEEDS 136 TO 165 MPH.
EF4...WIND SPEEDS 166 TO 200 MPH.
EF5...WIND SPEEDS GREATER THAN 200 MPH.
The image below depicts the greatest damage, from the southwest corner of Adel, northeast through about 3 miles southeast of Dallas Center. Then, a few points of scattered damage were found through Grimes.
Velocity Image at 6:23 pm CDT from the KDMX WSR 88D Radar. The bright green colors moving into southwest Adel show the potential for 60+ mph winds moving through the southern and central portion of the city.
Storm Relative Velocity Image at 6:33 pm CDT from the KDMX WSR 88D Radar located to the northeast of the area. The green is inbound movement towards the radar and the red and yellow are outbounds away from the radar. The image below shows rotation northeast of Adel near time of a brief tornado touchdown.
Storm Relative Velocity Image at 6:37 pm CDT from the KDMX WSR 88D Radar. Same as above image but near end of the 1.5 mile tornado track. Once again, the green is inbound movement towards the radar and the red and yellow are outbounds away from the radar.
Velocity Image at 6:51 pm CDT from the KDMX WSR 88D Radar. Rotation redevelops near Grimes with damaging straight line winds causing tree damage on the northeast quarter of town. Often times, these areas of rotation will cause damaging straight line winds at ground level. In this event, the areas of rotation caused damaging staight line winds with a brief tornado touchdown noted northeast of Adel.