Parkersburg-New Hartford, IA EF5 Tornado – May 25, 2008

Per the Storm Prediction Center Database, there have been 6 F5/EF5
tornadoes observed since 1950 in the state of Iowa.  The last one hit on May 25, 2008 and is the topic of this summary. 

General overview of the tornado track via the NWS Des Moines.  More detailed survey information listed below from a paper written by Tim Marshall.

• The massive tornado which eventually grew to over a mile wide began near the Butler/Grundy County line, 2 miles south of Aplington at 4:48pm CDT.
• Within 8 minutes, the tornado had grown to almost 3/4 of a mile wide as it moved into the southern end of Parkersburg.  A third of the town experienced tremendous damage.   
• At 5:09pm, the twister moved just north of New Hartford causing structural and tree damage.  It weakened east of town and traveled into northern Black Hawk County staying north of Waterloo and Cedar Falls. 
• During this time, significant straight lines winds were produced from a large rear flank downdraft just south of the tornado track.  A wind gust of 93mph was measured at the Waterloo Airport.
• North of Dunkerton, the tornado strengthened once again and reached its max width of close to 1.2 miles. Tremendous damage occurred to a farmstead in this area. 
• The tornado lifted at 5:50pm SW of Fairbank near the Black Hawk/Buchanan County line.
  

The official path length is listed as 40.97 miles.  A few other sources though, including Storm Data and the detailed survey from Tim Marshall have a path of 43 miles.

A satellite tornado was observed by storm chasers and an off duty NWS employee south of the main tornado.  It traveled about a mile in Grundy County.

Per the NWS summary in Storm Data:  “At least 627 homes were damaged, including 288 homes destroyed in Parkersburg, 88 in New Hartford, 15 in Hazelton and another 50 in Black Hawk County.  In addition, 58 had major damage, 33 had moderate damage, 2 were inaccessible, and 93 damaged but able to be occupied.  There were also 21 businesses destroyed.  Governor Chet Culver declared both Butler and Black Hawk disaster areas with both given the State Declaration.  A Federal Disaster Declaration occurred two days later for both Butler and Black Hawk Counties.”

An initial survey team was deployed on Monday, May 26 at 10am.  40+ damage indicators were identified during the survey.  In parts of Parkersburg and New Hartford, low end EF5 damage was discovered.  Additional investigations occurred including one led by Tim Marshall.  He presented a paper on how the rating was determined with Karl Jungbluth (NWS Des Moines) and Abigail Baca (Risk Management Solutions).  Per the paper, “Difficulties in rating homes arose since several homes were not anchored and slid off their foundations.  Also, there was significant clean-up of debris within one to two days after the tornado, even in the midst of inclement weather.”

The survey determined that the tornado traveled to the ENE for approximately 70 km (43 miles).  98% of the track was over rural farmland. The remaining 2% was over the south end of Parkersburg.  “Spiral ground marks were observed in many fields where corn stubble had been gathered indicating this was a multi-vortex tornado.  Complex flows were recorded in the corn stubble revealing sudden changes in the tornado’s path and even one loop.”  Additional highlights from this survey.  Note any pictures below come directly from this survey:

• The tornado moved into the SW corner of Parkersburg around 456pm CDT, traveling eastward along Highway 57/14.
• The tornado’s intensity increased at the east end of town as more debris was ingested into the twister.
• A wind row of debris was noted in open corn field east of town.
• Large grain silos filled with corn were hit east of town.

• The tornado then tracked through river bottoms uprooting and breaking hundreds of trees.
  
• It then moved north of New Hartford where more than a dozen homes were completely destroyed.
• 3 miles east of New Hartford, the tornado’s path narrowed and it turned quickly to the south before moving back to the ENE.
  
• Two more abrupt turns were observed to the southeast before the tornado moved toward Highway 63.
  
• After crossing the highway, “the ground spirals tightened, and became oblong in shape.  Then the tornado made an S-shaped turn to the north before moving northeast.”

• The tornado then widened and made a loop and a satellite vortex formed.
• Moved back to the ENE and dissipated SW of Fairbanks.
  

There were 9 confirmed fatalities.  7 were in the Parkersburg area and 2 in New Hartford.  Two deaths occurred a few days after the tornado hit and the last fatality was reported on November 7, six months after the tornado.  Per the NWS, a 61-year-old woman, was injured in the stairwell of her home.  A 2×4 was thrown through her right side lung.  She died of complications from her injuries.

In an article on extremeplanet.me entitled, “The List of the Strongest Tornadoes Ever Record:  Part III”, Parkersburg landed at #11 out of 20.  The town’s mayor is quoted from a 2008 NY Times article.  He states that most of those killed in Parkersburg were in their basements.  “Many of the destroyed homes were swept completely away, floorboards and all, exposing people who had taken shelter underground to the full force of the tornado.”