Monday, May 26, 2008

Preliminary Damage Survey Report of Iowa Tornado

Large Destructive Tornado Impacts Butler and Black Hawk Counties
A large and destructive tornado moved across Butler and Black Hawk counties
on Sunday May 25th. The initial touchdown occurred near the Butler and
Grundy county line, 2 miles south of Aplington at 4:48 pm CDT and quickly
grew in size and intensity as it approached Parkersburg. The tornado was
nearly 3/4s of a mile wide as it moved through the southern end of
Parkersburg at 4:59 pm CDT. Significant structural damage occurred in the
town of Parkersburg including 100 to 200 homes destroyed. The tornado
maintained size and intensity as it move towards New Hartford. At 5:09 pm
CDT the storm moved just north of New Hartford once again causing
significant structural and tree damage. The tornado weakened around 3 miles
east of New Hartford with lesser damage as it moved east to north of the
Waterloo and Cedar Falls area. Significant straight line winds occurred
along and just south of the tornado track with preliminary estimates of 90
to 100 mph. The tornado then grew in size to near 1.2 miles wide north of
Dunkerton causing substantial damage to a farmstead there. The tornado
continued to do damage as it moved into Buchanan County.
PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE DES MOINES IA 347 PM
CDT MON MAY 26 2008...PRELIMINARY DAMAGE SURVEY RESULTS FOR BUTLER AND BLACK
HAWK COUNTIES...THE STORM SURVEY INVESTIGATION IS STILL ONGOING AND WILL
CONTINUE ON TUESDAY. FINAL RESULTS ARE EXPECTED TO BE RELEASED LATE TUESDAY
AFTERNOON.......THE FOLLOWING IS A PRELIMINARY ASSESSMENT FOR THE DAMAGE
THAT OCCURRED OVER BUTLER AND BLACK HAWK COUNTIES ON MAY 25TH.* EVENT DATE:
MAY 25TH* ESTIMATED START TIME: 4:48 PM CDT* EVENT TYPE: POTENTIALLY GREATER
THAN EF3 PENDING FURTHER ASSESSMENT ON TUESDAY.* EVENT LOCATION: 2 MILES S
APLINGTON TO PARKERSBURG TO NEW HARTFORD AND ACROSS NORTHERN BLACK HAWK
COUNTY.* PEAK WIND: POTENTIALLY GREATER THAN 165 MPH PENDING FURTHER
ASSESSMENT ON TUESDAY.* AVERAGE PATH WIDTH: PATH WIDTH RANGED FROM 0.6 TO
0.7 MILES NEAR PARKERSBURG TO JUST NORTH OF NEW HARTFORD. THE PATH
CONSTRICTED TO NEAR ONE QUARTER MILE WIDE EAST OF NEW HARTFORD TO NORTH OF
WATERLOO. PATH INCREASED TO NEAR 1.2 MILES WIDE NORTH OF DUNKERTON BEFORE
DISSIPATING NEAR THE BLACK HAWK AND BUCHANAN COUNTY LINE.* PATH LENGTH: 43
MILES* INJURIES: PRELIMINARY 70* FATALITIES: PRELIMINARY 6*
DISCUSSION/DAMAGE: SIGNIFICANT STRUCTURAL DAMAGE OCCURRED ACROSS THE
SOUTHERN END OF PARKERSBURG AND ALONG A PATH TO JUST NORTH OF NEW HARTFORD.
NUMEROUS STRUCTURES COMPLETELY DESTROYED FROM PARKERSBURG TO NEAR NEW
HARTFORD. THE TORNADO CONTINUED EASTWARD TO JUST NORTH OF THE WATERLOO AND
CEDAR FALLS AREA. SIGNIFICANT DAMAGE ALSO OCCURRED NORTH OF DUNKERTON WHERE
THE TORNADO INCREASED TO ITS GREATEST PATH WIDTH. THIS STORM ALSO PRODUCED
SUBSTANTIAL STRAIGHT LINE WIND DAMAGE ALONG THE SOUTHERN PERIPHERY OF THE
STORM JUST SOUTH OF THE TORNADO TRACK. PRELIMINARY ESTIMATES THAT STRAIGHT
LINE WINDS OF 90 TO 100 MPH OCCURRED WITH THIS STORM. AT 537 PM CDT THE
WATERLOO AIRPORT RECORDED A 93 MPH WIND GUST. INITIAL SURVEY RESULTS
SUGGEST THAT STRAIGHT LINE WIND DAMAGE WAS THE CAUSE OF THE SEVERE DAMAGE
AT THE RECREATIONAL VEHICLE DEALERSHIP NORTH OF CEDAR FALLS. ADDITIONAL
DETAIL WILL BE ADDED TO THIS REPORT ON TUESDAY ALONG WITH FINAL EF SCALE
RATING RESULTS. ADDITIONAL INFORMATION INCLUDING IMAGES WILL BE POSTED AT
THE NATIONAL WEATHER SERVICE DES MOINES WEBSITE LATER TODAY AT:
WWW.CRH.NOAA.GOV/DMXFOR

REFERENCE...THE 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.
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