The storms formed within a “ring of fire” pattern, which features relentless waves of powerful storms rising above a persistent “heat dome” of high pressure. Extreme heat warnings blanket the lower Mississippi Valley, where triple-digit temperatures will combine with tropical humidity to push heat indices above 115 degrees.
That heat and humidity is fueling storms, which remain in the forecast through the weekend. Thursday was labeled a derecho, as it caused damage along a continuous path of more than 400 miles and gave hurricane-force winds.
The worst was felt in Illinois, where storms raced down the highway in the early afternoon. Here's a look at the worst wind gusts:
- 100 mph — Good Hope, Ill.
- 100 mph — Swan Creek, Ill.
- 100 mph — Kahoka, Mo.
- 100 mph — Adrian, Ill.
- 100 mph — Scotia, Ill.
- 100 mph — Roseville, Ill.
- 90 mph — Adrian, Ill.
- 88 mph — Good Hope, Ill.
- 82 mph — Holyoke, Colo.
- 82 — Lake of the Woods, Ill.
- 80 mph — Mooar, Iowa
- 80 mph — Lerna, Ill.
- 77 mph — Vermillion, Kan.
- 77 mph — Corning, Kan.
⛈️🌬️ The intense, long-lived mesoconvective system, which lasted more than 24 hours, originated from a tornado-producing supercell and developed into a broad arc and appears to have met the new, more stringent criteria #derecho pic.twitter.com/dMdrMSQVBD
— Stu Ostro (@StuOstro) June 30, 2023
The derecho began as a rotating supercell storm that spawned a tornado near Kimball, Neb., Wednesday afternoon. It then proceeded east along the Kansas-Nebraska border, surfing jet stream winds to the east. Storms began to feed into this jet stream, mixing it up at the surface in the form of damaging wind gusts.
Strong winds caused the earring line to rise outward in the middle, arcing and taking on a backward C shape. By midnight Thursday, it had begun to produce hurricane-force winds. It then accelerated eastward, with forward speeds in excess of 65 mph. The Storm Prediction Center added a Level 4 out of 5 red zone to its outlook for severe weather around midday, struggling to keep up with the rapidly evolving forecast.
Derechos are notoriously difficult to predict. While it's proven that a combination of warm, humid weather and strong winds is the recipe for their birth, forecasters still struggle to figure out when storms will take full advantage of these ingredients.
Perhaps the most significant derecho in a generation to hit Iowa on August 10, 2020. Winds of up to 140 mph hit Cedar Rapids, causing the damage typically seen with EF3 tornadoes. The storms caused $11.2 billion in damage, destroyed 42 percent of Iowa's corn crop and killed four people. This derecho ran 770 miles from the Iowa-Nebraska border to the gauntlet of Michigan.
Derecho season in the Midwest and plains runs from late May through September. They are often compared to inland hurricanes, as their wind effects can be just as far-reaching and devastating.
