The remnants of Hurricane Helene were not the only factor contributing to the severity of the flooding that struck the mountain community of Asheville, North Carolina.

Several conditions in the region, including a precursor rainfall event and the country’s topography, led to deadly flash flooding, experts told ABC News.

Hurricane Helene barreled through Big Bend, Florida, on September 26 as a Category 4 hurricane, bringing winds of 140 miles per hour and a 15-foot storm surge to parts of the Gulf Coast. The hurricane illustrated the far-reaching impact a storm can have not only along the coast but also hundreds of miles inland. After making landfall, Helene moved north, reportedly producing tornadoes in five states and dumping over 30 inches of rain on parts of North Carolina within days.

Following Hurricane Helene, ABC News’ “Good Morning America” ​​will offer five days of special coverage called “Southeast Strong: Help After Helene” (#SoutheastStrongABC), highlighting the communities affected by Hurricane Helene across the Southeast and the pressing issues The focus is on efforts to help them recover.

When large hurricanes form in the Gulf, they tend to trigger a precursor rainfall event further inland, namely the system’s large rain cover — defined by the National Weather Service as “a solid or near-solid area of ​​rain that typically becomes heavier as the eye approaches.” is coming.” “—interacts with a cold front, Art DeGaetano, director of the NOAA Northeast Regional Climate Center at Cornell University, told ABC News.

According to the North Carolina State Climate Office, the Asheville region had already experienced heavy rain in the days before Helene, with more than a foot of rain falling in some places. As a result, the ground was saturated and rivers and streams filled to the brim as Helene, “the real hammer,” flowed over the area, DeGaetano said. When the French Broad River, which flows through Asheville, and its tributaries burst their banks, the water rushed into surrounding neighborhoods within minutes.

Although the phenomenon doesn’t happen often, it has happened in the region before, DeGaetano said. A similar event occurred in Asheville in what was known as the “Great Flood of 1916,” in which 80 people died.

Additionally, the sheer size of the storm system allowed areas to be hit by rain earlier and for longer, Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and former president of the American Meteorological Society, told ABC News.

The region’s mountainous topography also played an important role in the flooding, Yuh-Lang Lin, a professor of atmospheric sciences at North Carolina Agricultural and Technical State University, told ABC News.

Orographic uplift, a process that occurs when hills or mountains force air to rise and cool, caused water vapor to condense and additional precipitation to form as it connected to the tropical system Helene, Lin said.

This heavy moisture was then “pushed” out of the atmosphere and spread across the Asheville region in a short period of time, DeGaetano said. In hilly and mountainous terrain, rainfall is typically directed into valleys, rivers and streams, DeGaetano said.

“That’s where we see these extreme floods in places like that,” Jennifer Francis, an atmospheric scientist at the Woodwell Climate Research Center, told ABC News.

DeGaetano said climate change also likely played a major role in Helene’s storm behavior. The warm waters in the Gulf of Mexico helped the storm pick up even more moisture and strengthen as it got closer to shore, he said. The increased water vapor storage fueled the heavy rainfall along the Helene route.

Researchers are investigating whether an atmospheric river also contributed to the heavy rainfall, Shepherd said.

“You kind of had this multiple hurricane, this orographic uplift from the mountains and this atmospheric flow,” he said. “Trillions of gallons of moisture come from the tropics.”

According to the Federal Government’s Fifth National Climate Assessment published in November 2023, human-induced climate change is causing extreme rainfall to become more frequent and intense.

Rising global temperatures are accelerating the water cycle and bringing heavier rainfall – and associated flooding risks – across the US. More intense extreme rainfall events are increasing the frequency and severity of flash floods, in part because the inflow of water is greater than current infrastructure was built to handle.

Most places on the East Coast experienced an overall increase in precipitation due to climate change, DeGaetano said. In the Southeast, extreme precipitation events have increased by about 37% in recent decades, according to the National Climate Assessment.

ABC News’ Daniel Peck contributed to this report.