Hundreds of tornadoes and widespread floods have ravaged the U.S. Midwest and Great Plains states over the past couple of weeks. The flooding is breaking some weather records, and at least 38 people have been killed by tornadoes in the United States so far this year.
Blame climate change?
Scientists have been studying possible links between climate change and the frequency and ferocity of tornadoes.
Villanova University professor Stephen Strader says it is not yet clear how much influence the warming atmosphere and other changes have on these deadly storms.
In a VOA interview, the extreme weather scientist said, "We're not there from a scientific standpoint, yet." He said it does seem likely, but not certain, that we will see more severe weather of various kinds in the future.
National Weather Service (NWS) meteorologist Andy Foster in Kansas City, Missouri, says there has been "major record flooding" across much of the central U.S.
He told VOA that heavy snow cover melted and combined with large amounts of rain from "multiple storm systems" saturated the ground and caused river flooding. Foster said when still more major storms brought "copious amounts" of rain, there was nowhere for the water to go, sparking flash floods in several states, inundating roads, towns and farmland.
Storms that led to flooding also included an unusual flurry of tornado activity.
U.S. records show that destructive and deadly twisters are common during the spring months, particularly in an area called "Tornado Alley," which covers several Midwestern states. The midsection of the United States is where cold air from the Rocky Mountains collides with warm, moist air flowing up from the Gulf of Mexico -- prime conditions for tornadoes to form.
The mixture is part of the complex recipe for compact but powerful storms that tear roofs off buildings, toss huge trucks across farm fields, uproot trees and shred multistory brick buildings, all of which produce flying debris that can kill people.
Research scientist Harold Brooks says clusters of tornadoes occur every five or 10 years, but "the second half of May is going to go down as one of the busiest two-week periods on record."
In a phone interview from the NOAA National Severe Storms Laboratory in Norman, Oklahoma, Brooks said the clearest trend in the data is not more or stronger tornadoes, but more days each year with multiple storms.
Villanova professor Strader said scientists currently have a hard time predicting tornadoes even "a few hours before the event," so making projections about how many deadly storms may erupt years or decades from now is a daunting task.
As the annual death toll from tornadoes dropped significantly from the 1920s to the 1990s, the value of predicting violent storms has become more apparent. Brooks and other experts say lives have been saved through better forecasting, improved building codes and more effective warnings.
Strader said those improvements "stalled out" in recent years, prompting officials to seek better ways to educate the public and communicate timely, effective warnings. He said some people stay in mobile homes and other vulnerable places even after they get warnings in time to move to shelter.
As a start, weather experts are teaming up with social scientists to craft warnings that people will heed to find safety, either in a sturdy building or other safe place, Strader said.
"We're bridging the physical science with social scientists to really look at what we can do to continue to solve this tornado issue," he said.
An earlier version of this story gave an incomplete title for Harold Brooks. VOA regrets the error.