Climate change not only is causing more intense hurricanes, it also seems to stoke hurricanes that generate greater rainfall — and cause more flooding. Climate models predicted this phenomenon, which has been borne out by the deadly floods of Hurricane Harvey in 2017, Florence in 2018 and Imelda in 2019. The question has been “why?” 

A study by Princeton researchers recently teased out the answer: both the higher moisture content of warmer air and storms’ increasing wind speeds conspire to produce wetter storms. The work may improve planners’ ability to assess flood hazards in hurricane zones.

“This study makes a statement about the future,” said co-author Gabriel Vecchi, professor of geosciences and the Princeton Environmental Institute. “We’re having this convergence where our observations are starting to show the increased rainfall that our models have been predicting for quite a while, and now we also have a clear theoretical understanding as to why it should be happening.”

Potential changes in the frequency of occurrence and rainfall rates from tropical cyclones are major concerns for flood hazards in the United States, especially for urban regions along the Gulf and Atlantic coasts.