This swirling mass of clouds off the coast of South Carolina this afternoon is the remnants of a system that just wouldn't quit — it's traveled almost 2,000 miles from Colorado to the Atlantic Ocean over the past two days, leaving a path of damage, injuries, and two fatalities in its wake.
The storms began as supercells in eastern Colorado, producing several tornadoes, large hail, and damaging winds. One of the storms produced a wind gust of 111 MPH in the town of Hugo, southeast of Denver, damaging many structures and downing power lines.
The supercells coalesced and organized into a mesoscale convective system (MCS) — a highly organized complex of thunderstorms that often produces damaging straight-line winds — and and began to sweep southeast through Kansas.
The MCS was classified as a derecho, a widespread damaging wind event that stretches hundreds of miles, after it produced damage and reports of winds in excess of 70 MPH along a path from Kansas through northwestern Georgia.
The storm finally lost steam once it reached Atlanta, continuing to weaken last night until it finally exited into the Atlantic Ocean this afternoon.
Due to their efficient structure, mesoscale convective systems are known to travel extreme lengths and last for more than a day if conditions ahead of the complex allow the storms to sustain themselves. As we get deeper into the summer months, this kind of event will gradually replace supercells as the dominant force for severe weather in the United States.
[Images via GOES and SPC | h/t to Stu Ostro]