Scientists say the effects of Hurricane Harvey, which has been stalled over the Texas Gulf Coast since Friday and dumped more than 20 inches of rain in some areas, were worsened by a lethal confluence of meteorological events: warm water in the Gulf of Mexico that intensified the rainfall, and a lack of winds in the upper atmosphere that could have steered Harvey away from land.

Exacerbating the situation, said Hal Needham, a storm surge expert and founder of the private firm Marine Weather & Climate in Galveston, Tex., was that the storm surge elevated Galveston Bay, blocking drainage of the rain that pummeled coastal and inland areas.

“A two- or three-foot storm surge alone would not have been catastrophic,” Mr. Needham said. “It was all these ingredients coming together.”

And it’s not over.

Dennis Feltgen, a spokesman for the National Oceanic and Atmospheric Administration’s National Hurricane Center in Miami, said the driving rains would continue for another two or three days, pouring an additional 15 to 25 inches over parts of Southeast Texas. Some areas, he said, could see as much as 50 inches of rain.

“This is unprecedented,” he said.

Yet it does have some parallels. J. Marshall Shepherd, director of the atmospheric sciences program at the University of Georgia, said Harvey is very much like Allison, a tropical storm that flooded Houston badly in 2001 because it lingered over the city and dumped prodigious amounts of rain.

“In some ways, I think this event is going to far surpass what we saw in Tropical Storm Allison,” Dr. Shepherd said. The atmosphere is not helping to push it anywhere else. “The steering currents that would normally lift it out of that region aren’t there,” he said.

Hurricanes are essentially large weather engines fueled by the warm waters of the ocean below.

The mind-boggling amount of rainfall during Harvey is a function of the storm sitting by the Gulf of Mexico and continuing to draw moisture directly from it. Because of the orientation of the storm, Dr. Shepherd said, “you’ve just got this stream of moisture firehosing into the Houston region,” as the moisture is constantly replenished by the gulf. “This could go down as the worst flood disaster in U.S. history.”

Scientists are increasingly able to link some extreme weather events to climate change, but when it comes to hurricanes, many say there remain a number of unknowns. What is clear, though, is that rising global temperatures warm the oceans, which causes more water to evaporate into the atmosphere.