Integrated Vapor Transport (IVT) Boosts Moisture Air Currents Can Carry; WV In Bullseye Of New Rainfall Conditions [View all]

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Across McDowell County, the rising water wrecked roads and bridges and left residents stranded. It swallowed cars and trucks, sent debris downstream, flooded homes and claimed three lives, including that of a 2-year-old boy. In the town of Welch, the flood swamped city hall, the library and the sheriff’s station. It also blocked the main road to the hospital. This time, the devastation carried the fingerprints of a mostly invisible but profound atmospheric shift: As the air gets warmer and wetter over time, states within central Appalachia lie within a region particularly vulnerable to the extreme rainfall and the flooding that often follows.

To understand how that increasing moisture in the skies has driven these downpours, The Washington Post examined a metric called integrated vapor transport (IVT) — which characterizes where plumes are flowing from and their intensity. Across much of the planet in recent decades, the analysis has found rising temperatures and shifting wind patterns have waterlogged the atmosphere, raising the odds for more destructive, torrential rainstorms that can cause floods.

That is true in swaths of the eastern United States, as well as parts of California and other states in the Intermountain West, where atmospheric rivers rising from the Pacific Ocean are slamming into the region with increasing force. But some hot spots in the American West and Northeast are wealthier and have homes and businesses distributed over a wider area, which help make them less vulnerable to punishing storms. In central Appalachia, the changes high above are exacerbating devastation below in an area where mountainous terrain, widespread poverty and infrastructure built along snaking waterways makes preparing for floods difficult — and recovering from them that much tougher.

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The broader hot spot in the East is one of the longest ones in the world — stretching about 2,000 miles from Florida to Newfoundland, an expanse that is home to roughly 131 million people. Trends dating to 1992 show that central Appalachia sits in an area where this conveyor belt of moisture has increased at some of the highest rates anywhere in the nation. A Post analysis of 75 years of rain gauge data for central Appalachia shows that the area now experiences about two more days of heavy rainfall each year, a 35 percent increase compared to 1950.

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https://www.washingtonpost.com/weather/interactive/2025/flood-hotspots-appalachia-eastern-us-maps/

https://wapo.st/47MDvXi