One Hail of a Day

View from my car at 2:33 p.m. MDT May 21
just west of Denver International Airport

Yesterday was a first in my long career and interest in the weather. It occurred as I was returning home from a meeting in Colorado, a meeting coincidentally about CoCoRaHS and related programs. The sky was dark as I drove south on I-25 toward Denver, but it appeared more ominous as I headed east from I-25 toward Denver International Airport. I encountered some rain about 10 miles out and witnessed a few spectacular cloud-to-ground lighting strokes. About 2:30 p.m. I was within five miles of the airport when small hail began falling. The hail became more intense and I was seeing 1/4 to occasionally 1/2 inch hail. Traffic slowed to a halt as the hail continued and began to pile up on the ground.  By time it ended about 20 minutes later there was 3 to 4 inches of hail covering the ground and the road. In other areas, the hail was estimated to be 8 inches deep or more. I've never experienced hail like this before.

Hail on Pena Blvd approaching Denver International Airport at 3:23 p.m. MDT
Photo by Nancy Selover

The hail covered a fairly large area, including the at and around the airport terminal. Many flights were cancelled and many more delayed because of this storm. A number of the cancelled flights were due to damage to aircraft by the hail. Automobile traffic in and out of the airport was at a crawl because of the accumulation of hail. In some places, roads were flooded when hail clogged the storm drains.

At the same time, a rain-wrapped tornado was on the ground about 8 miles south of the airport moving east along I-70. I wasn't aware of this until I made it into the airport terminal.  The radar image below is probably sometime around 2:00 p.m. MDT. The area outlined in pink is the tornado warning. The storm was moving northeast and there were multiple reports of rotation.

Radar image about 2:00 p.m. MDT May 21.
Credit: NWS Denver/Boulder

This image was the radar at 3:24 p.m. MDT.  The storm has cleared the airport and remains intense. The tornado icons along I-70 are locations where spotters reported a tornado.  This storm complex continued on for several more hours. Interestingly this was the second consecutive day where a severe storm moved right over the Denver airport.

Radar image at 3:24 MDT May 21.

My phone had been alerting me about severe thunderstorm warnings back home as I made my way
through the terminal.Once checked in and through security I fired up my laptop to check out the weather in Denver and back home. I soon learned that hail from 3 to 4 inches in diameter was falling from the skies just 20 or so miles southwest of my home in Champaign County, IL in the city of Tuscola. That was the really big stuff. Hail from 1 to 2 inches in diameter fell in many other areas. At Champaign's Willard Airport 1.75 inch hail and high winds (gust to 63 mph) produced significant damage to vehicles, and also damaged the World War II B-17 Liberator "Aluminum Overcast" which is visiting the area.
 

Photo of 2.5 inch hail by CoCoRaHS observer
at IL-DG-11 in Douglas County, IL

3 to 4 inch hail in Tuscola, IL on May 21.
Photo by Brooke Messer, via JC Fultz, WAND-TV

Denver and my home in Illinois were the focus of my attention yesterday, but they weren't the only locations with severe weather and large hail. Hail measuring from 2.00 to 2.75 inches was reported in southern Illinois, Indiana, and Ohio.

Large hail was also reported today, this time in Pennsylvania and New York.  The largest hail was in Amsterdam, NY where hail three and four inches in diameter was reported this afternoon.