The continental United States just experienced its wettest 12 months on record, receiving 6.25 inches of rainfall above the mean, according to a new report by NASA’s Earth Observatory. The finding comes amid weeks of record-setting floods throughout much of the central United States.
From May 1, 2018 to April 30, 2019, the contiguous U.S. averaged 36.20 inches of precipitation ― more than half an inch higher than the previous record-setting year (April 2015 to March 2016) and the most in 124 years of modern record-keeping. Ten U.S. states had their wettest 12 months on record, with the highest precipitation rates in the Mid-Atlantic and Midwest regions. According to the U.S. Drought Monitor, just 2.33 percent of the continental U.S. was in drought at the end of April, compared to nearly 30 percent at the same time last year.
“I do not have an explanation for the weather systems that caused the heavy precipitation, but sea surface temperatures in the western Atlantic and Gulf of Mexico have been generally well above normal over the past year,” climatologist Ken Kunkel said in a statement . “This has surely added to the atmospheric water vapor content available to the precipitating weather systems.”
Over the past two weeks, flooding along the Arkansas, Missouri, and Mississippi rivers has inundated riverside communities throughout the central U.S. Flood watches and warnings have been issued in at least 7 states, and Arkansas Governor Asa Hutchinson has declared a state of emergency amid hundreds of evacuations and at least one death.
This month’s heavy rainfall has already broken eight local records for May precipitation and threatens to break records for any single month in areas of Arkansas, Kansas, Missouri, and Oklahoma.
While this year’s historic flooding seems “somewhat of a random occurrence,” meteorologist Jason Samenow wrote in the Washington Post, it has also “occurred against a longer-term backdrop of climate warming and increasing precipitation extremes. In other words, climate change probably intensified the rain and increased the chance it would become a record breaker.”
— Noah Goodman