It has been quite a spring for twisters in the United States. So far this year, the preliminary tally from the Storm Prediction Center has reached 1,035 tornadoes, with 872 of them occurring in April and May.
And we've still got another peak month of activity left to go.
One of the most destructive of this season's tornadoes spun up on Tuesday, May 21 in southwestern Iowa. It then carved a destructive 44-mile path to the northeast, ultimately rampaging through tiny Greenfield, population 2,062. Spinning at 185 miles per hour, the EF-4 twister reached a terrifying maximum extent of more than a half mile wide.
Tragically, it killed five people in Greenfield.
The gash it cut through the town is seen in the satellite image above, and also in this one released by NASA today:
This spring's tornadic toll has been driven by the clash of two air masses: relatively cool air to the north and west, and a gigantic, stagnant, high-pressure dome of hot air parked over Mexico and the U.S. Gulf States. The jet stream coursing between these clashing air masses has swept a series of storm systems through Texas, Oklahoma and up into the Midwest.
The result: huge thunderstorms with powerful convective updrafts that propelled moist air high into the atmosphere — sometimes into the stratosphere in a phenomenon called overshooting cloud tops.
"When this type of updraft ingests a very unstable airmass with large vertical wind shear, catastrophic tornadoes and large hail are often the result," says Kristopher Bedka, an atmospheric scientist at NASA’s Langley Research Center, quoted in a post at NASA's Earth Observatory.
Preliminary data shows that there have been four days with at least 30 tornadoes rated EF-1 or stronger in the United States. The average is two annually. According to Harold Brooks of the National Severe Storms Laboratory, quoted in a story in USA Today, that likely puts 2024 in the top 10 percent of years.
