Tropical cyclones are becoming sluggish
06 June 2018
The speed at which tropical cyclones travel has slowed globally in the past seven decades, especially over some coastlines. This effect can compound flooding by increasing regional total rainfall from storms.
Tropical cyclones are among the deadliest and costliest of disasters, causing destruction not only from strong winds, but also from flooding and mudslides associated with storm surges and heavy rainfall. The total amount of storm rainfall over a given region can be extreme, regardless of the maximum storm wind speeds; it is proportional to the rainfall rate and inversely proportional to the translation speed (how quickly a tropical cyclone passes over a region). Some studies have investigated trends in heavy rainfall from tropical cyclones over the past century and future projections in tropical-cyclone rainfall rates, but the translation speed has received less focus. In a paper in Nature, Kossin investigates global trends in tropical-cyclone translation speed, and regional trends over individual ocean basins and adjacent land. He finds that translation speeds have slowed, suggesting that the total amount of regional rainfall from tropical cyclones might have increased.
Image credit: NASA/SPL - Hurricane Harvey seen from space