The Atlantic hurricane season brought above-normal activity but was benign for the US as only one tropical storm crossed the continental coastline, experts at Colorado State University say.

Tropical Storm Chantal caused $US500 million ($774 million) of damage in the first season since 2015 without a US hurricane landfall.

The university says the season was above-normal based on the number of major hurricanes and accumulated cyclone energy, with activity probably driven in part by warmer than normal sea surface temperatures in the tropical Atlantic and Caribbean.

The season included 13 named storms, five hurricanes and four major hurricanes, which compares to a 1991-2020 average of 14 named storms, seven hurricanes and three major hurricanes.

All four major hurricanes reached at least category 4 intensity, with Erin, Humberto and Melissa hitting category 5. The four all underwent extreme rapid intensification.

“While there was extensive tropical cyclone activity in the western half of the basin, the only hurricane with widespread significant impacts was Melissa,” the university said.

Melissa caused damage estimated at $US6-$US7 billion ($9.3-$10.8 billion) after hitting Jamaica at category 5. It also affected Cuba and Hispaniola. 

Researcher Phil Klotzbach says the season was “relatively well-predicted” in the university’s seasonal outlooks, although it somewhat overpredicted the number of hurricanes while underpredicting the time they would spend at major intensity.