Though separated by nearly 1,000 miles, these two extreme weather incidents are examples of the same phenomenon: human-caused climate change supercharging extreme rainfall events. And these types of extreme rainfall events are likely to become more common, too, as long as the planet continues to get hotter.
Krissy Hurley, a meteorologist for the National Weather Service, told CNN that one of the biggest factors contributing to this amount of rain was that the atmosphere had ample moisture to work with.
When meteorologists launched a weather balloon over the weekend to collect data, they found the moisture in the air was at record levels — a “recipe for disaster,” according to Hurley.
The flooding was caused by several storms that developed one after the other over the same area, which took advantage of that moisture and led to extreme rainfall rates.
“We had a stationary boundary set up over western part of middle Tennessee that provided the perfect set up conditions,” said Mark Rose, a meteorologist with the National Weather Service. “A constant training of [storms] over that one area for several hours right along that boundary.”
Heavy rainbands associated with the leading edge of then-Hurricane Henri resulted in a torrential downpour in New York City. Between 10 and 11 p.m., 1.94 inches of rain fell in Central Park, setting the all-time record there for the largest amount of rain in a single hour, according to the National Weather Service.
In total, 4.45 inches of rain fell in the city on Saturday night, also setting a record for the date — the old record of 4.19 inches had stood since 1888.
These extreme rainfall rates are becoming more common because of human-caused global warming, scientists say. According to the UN’s report on climate change, “the frequency and intensity of heavy precipitation events have increased since the 1950s over most land area.”
CNN’s Eric Levenson contributed to this report.
