Roanoke, IL F4 Tornado – July 13, 2004

An F4 tornado developed rapidly in a highly unstable atmosphere and devastated everything along its 9.6 mile path through Woodford County, IL on July 13, 2004.  It began 1.75 miles NNE of Metamora and traveled generally in a southeasterly direction.  The tornado reached F4 intensity as it crossed Route 117 and demolished the Parsons Manufacturing Plant. There were 140 people in the plant at the time and all made it to storm shelters in time.  Per the NWS Summary, they arrived 3-5 minutes before the tornado arrived.  “Steel beams and metal siding from the plant were found approximately 3/4 mile east in a farm field.”

A paper found in the Natural Hazards Center Library discusses the proactive safety plan that was in place at the Parsons Plant and how the implementation of that plan saved lives.  There were no fatalities with this event and only 3 injuries reported.  Here are a few highlights in regards to the severe weather safety plan at Parsons:

• The company had 3 reinforced concrete shelters.  
• They established an Emergency Response Team (ERT) in 2000.
• 2 individuals in the accounting department monitored the NOAA Weather Radio.
• If a Severe Thunderstorm/Tornado Warning was issued for Woodford County, the ERT Coordinator or plant Safety Manager was informed.  
• Trained weather spotters were sent outside to assess the threat.
• If the threat seemed imminent and announcement was made 3 times, production was halted and all were to move to their designated shelter.

Here is the full paper on their plan.  All companies could learn a great deal from the Parsons Plant Warning Process.  

After hitting the Parsons Plant, the tornado continued its trek devastating farmsteads.  2 farmsteads near the plant had the 2-story homes leveled with only debris remaining in the basements.  The tornado approached Roanoke from the SW.  It tracked south of town causing significant damage to a barn and another farmstead.

I found a very detailed paper written by members of the NWS Central IL about this event.  It is entitled, “The July 13, 2004 Tornado event:  Analysis of Tornadogenesis in a Highly Unstable Environment.” Read the full paper here.  

Their analysis showed a unique weather set-up for this event.  A small shower developed into a supercell with an F4 tornado in less than 30 minutes.  “Intersecting boundaries, the high levels of instability, and the environmental and storm-scale storm relative helicity were critical players in producing the resultant tornado.”