Wednesday, August 28, 2013

23 Years Ago: The Only F-5 Tornado to Occur in August: Plainfield, IL

On this date in 1990, an F-5 tornado struck the community of Plainfield, IL, causing extensive damage.  The tornado killed 29 people and injured over 300 more.  To this day it is still the only F-5 (now called EF-5) tornado known to occur anytime during the month of August in the United States.

Steve L., the pilot of a Cessna 172, took the aerial photos above and below along the damage path in Plainfield a few days after the tornado took place:

The path of destruction was 16 miles long and 600 yards wide at one point as the tornado tracked from Northwest to Southeast across the area during the late afternoon hours:

The National Weather Service (NWS) was heavily criticized for failing to warn of the tornado in this particular event.  Back at the time, the area that is now covered solely by the NWS Office in Chicago was split between that office and one in Rockford, IL.  The Rockford office performed quite well, giving advanced warning of a tornado that was produced by the same thunderstorm over that part of the region.  As the storm moved into NWS Chicago's area of responsibility, the warning performance degraded significantly.

The NWS's own "service assessment" report following the event was rightfully hard on the Chicago office, as you can see in the excerpt below:

At the time that was the harshest criticism I had ever read in a NWS service assessment (of itself), and I don't think it's been surpassed to this date (if anything, the NWS has become "easier" on itself in subsequent service assessments).

In its defense, the NWS in Chicago pointed out that the Storm Prediction Center (which was then called the National Severe Storms Forecast Center) had issued a Severe Thunderstorm Watch instead of a Tornado Watch for the region that afternoon.

While "only" one supercell storm produced tornadoes within the watch area on that day, the Plainfield EF-5 tornado was one of them.  Hence the reason that I always caution folks not to let their guard down, particularly when dealing with an isolated, supercell storm.

You can be that residents of the area will never forget that day, nor are they likely to let their guard down "just because" there isn't a Tornado Watch in effect - and who can blame them, especially after seeing images like these:

This was also one of the last tornadoes to be examined by the late Dr. Ted Fujita, the preeminent tornado researcher and damage survey pioneer of our lifetime (creator of the Fujita "F-Scale").

You may find it surprising that the F-5 rating was arrived upon by Dr. Fujita's examination of damage to a corn field, rather than by any structural damage within the city itself:

Dr. Fujita gave a presentation on the Plainfield tornado as shown in the following YouTube video.  This was one of his last formal presentations which was held at the 3rd Tornado Symposium in Norman, OK back in 1991.  I had the great pleasure of attending that meeting and seeing his presentation in person.  If you have the time and interest, I highly recommend viewing it at some point as it gives a lot of great information on this event:

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Anonymous said...

I was witness to the Plainfield storm at its beginning. I was in downtown Aurora to the NW of where the tornado later touched down. I was making a stop on the Fox River when I could see the horrific black, really black, clouds following me eastward. Winds were coming up too and had blown an a-frame sign down the block. I got the sign, returned it to the owner, and went on to work in West Chicago (the small town). That afternoon, while on break about 2 1/2 hours later, I commented to a co-worker that my ears were popping, and I heard the stock room radio blare a tornado warning for south of Naperville. Now jump forward to the next day. At work again, one co-worker was breathing a sigh of relief she and her husband were looking at properties in Plainfield a few days earlier. Her realestate agent told her that the property they had looked at in one location was now completely destroyed by the tornado. Fortunately, she hadn't yet put down earnest money. One other co-worker told me she came out of her house in time to see the school "breathe" and then collapse in on itself with a few people still inside.

It was a terrifying storm BEFORE the tornado. I can't even imagine how terrifying it was DURING it!

Anonymous said...

I forgot to mention that on the day of the tornado, after I got home, I found out that we had been blasted with quarter-sized hailstones. LOTS of them. Our house, with painted siding, showed where each iceball hit, spalling off the paint in large round divots on the wood. Our old window air conditioner looked like someone had strafed it with gunfire from above, and so did the house.