Such accelerated development can result in a stronger storm and increase its potential devastation, researchers at Texas A&M University reported Monday.
The researchers examined tropical cyclones for the decade 1998-2007, with particular attention to Hurricane Omar, a Category 4 hurricane that formed in 2008 and eventually caused about $80 million in damages in the south Caribbean area.
They analyzed data from the oceanic region under the storm, including the composition of ocean water.
"We were looking for indications that the storm increased in intensity or weakened and compared it to other storms," atmospheric scientist Ping Chang said.
"This is near where the Amazon and Orinoco Rivers flow into the Atlantic Ocean, and there are immense amounts of freshwater in the region.
"We found that as a storm enters an area of freshwater, it can intensify 50 percent faster on average over a period of 36 hours when compared to storms that do not pass over such regions," he said.
The findings could help in predicting a hurricane's strength as it nears large river systems that flow into oceans, such as the Amazon in the Atlantic, the Ganges in the Indian Ocean or the Mississippi River into the Gulf of Mexico, the researchers said.
"If we know a hurricane's likely path, we can project if it might become stronger when nearing freshwater regions," Chang said. "This is another tool to help us understand how a storm can intensify."