20 Years Since the Plainfield Tornado

By -

Tomorrow commemorates the 20th anniversary of the Plainfield, Illinois, tornado. It is the only F-5 intensity tornado ever to occur in the month of August and it struck without warning. Because of the lack of warning, 29 people died and 353 were injured even though it occurred in mid-afternoon.

Why was there no warning? There were a number of factors but the most important was the geographic separation between the radar in Marsailles, IL and the warning meteorologists in Rosemont. The image above is from the Marsailles radar while the giant tornado was on the ground. The (likely) hook echo is not seen in this image because it is in the ground clutter (I have outlined the likely shape of the tornadic thunderstorm in pink below).
The radar "technician" in Marsailles did not know to tilt the antenna up to a higher angle to eliminate the clutter and make the potential tornado visible. Because the meteorologists in Chicago could not see the hook and because there were no spotter reports of a tornado, they didn't issue a warning. A later investigation indicated that some law enforcement agencies knew about the tornado but didn't report it to the NWS because they assumed the NWS already knew.

After this and other fiascos (Big Thompson Canyon, Delta 191) with a large loss of life due in part to the separation of the radar and warning responsibility, the National Weather Service underwent a reorganization in the mid-1990's the eliminated this problem. I tell this story in detail in Warnings: The True Story of How Science Tamed the Weather. 

The Chicago Tribune has this article about the tornado and its damage and a second article about why, if the same tornado were to occur today, there would certainly be a warning. The latter article mentions Warnings.


The image below, from the NWS in Chicago, shows the telltale brown grass caused by the high winds and scouring in a major tornado.

Paul Sirvatka, out storm chasing that day, captured the initial development of the tornado.
The entire video can be viewed here. For those from outside "tornado alley" who have never seen the "green sky" associated with extreme hailstorms and tornadoes, I highly recommend viewing Paul's video as it captures the green sky well.  

We can be thankful that weather science and technology have advanced to the point where a similar event -- entirely unwarned -- is highly unlikely in the future.  

Comments

Post a Comment

Popular posts from this blog

Hilary's Forecast Path Shifts West; Updated 9:20am PDT

By -
Image
The forecast path of the center of Hilary has shifted a bit to the west. This increases the threat to the Southland, especially in terms of flooding.  Rainfall Note the heavy rains are forecast for Los Angeles County. Serious flash flooding may result. Because the forecast path has shifted to the west, that increases the threat of serious flooding in Los Angeles County north into Yosemite and the southern Sierra. It lessens the threat in Utah and western Arizona. While the threat of widespread flooding in Utah and Arizona lessens, note that some thunderstorms with localized heavy rain show up on the map.  In Nevada, the more western path increases the risk of serious flooding around Mt Charleston and into the central part of the state.  Here is the updated  (9am PDT) flash flood risk map. Wind There are already about 40,000 people without power in California, mostly in the center of the state.  The maps above are the peak gusts forecasted with the storm. The highest winds, in general,
Read more

Dangerous Travel Conditions - People Reportedly Stranded

By -
Image
-- Note, more current info available. Scroll up. --- Updated Information as of 8am PDT You are risking your life if you attempt to travel through the purple area.  While the rain has not begun in coastal California, I would urge you to use this time to make any preparations. Power outages have occurred already in southeast California. Here is the latest radar as of 7:55am PDT. As of 6:40am PDT , the radar indicates moderate to heavy rain falling over desert areas of Southern California and far western Arizona (click to enlarge).  Rainfall amounts for the 24 hours ending at 7am PDT show more than two inches have already fallen. There are reports from reliable sources that roads are already washed out and that people are stranded in isolated parts of the desert.  Below is a high-resolution computer model's rainfall forecast from 5am PDT to 11pm PDT Sunday. More than a foot of additional rain is forecast to fall. This will lead to catastrophic flooding.  Here is a map of current watc
Read more

Update on Tornado and Wind Potential; 12 Noon PDT

By -
Image
There was at least one tornado and at least one funnel cloud yesterday.  --- original forecast --- Hilary (the swirly symbol) continues to move NNW paralleling the coast of Baja California, Mexico. The area outlined in red has a significant risk of tornadoe s the rest of the afternoon.  Below is a list of peak wind gusts so far.  Peak winds may increase farther north as the afternoon progresses.  Addition at 12 noon PDT: Sure enough, winds have increased.  Note: If you are in the San Diego area, I recommend not  traveling east on I-8. Heavy rains may cause flash flooding that will involve the highway. 
Read more