These dates, adopted by convention, historically describe the period in each year when most subtropical or tropical cyclogenesis occurs in the Atlantic Ocean (over 97%).
The National Hurricane Center (NHC) will begin issuing regular Tropical Weather Outlooks on May 15, 2025, about two weeks prior to the start of the season.
Broadly speaking, ACE is the measure of the power of a tropical or subtropical cyclone multiplied by the length of time it existed.
ACE is only calculated for full advisories on specific tropical or subtropical cyclones reaching wind speeds of 39 mph (63 km/h) or higher.
On December 10, 2024, Tropical Storm Risk (TSR) released its extended range forecast for the 2025 season, predicting an average season with fifteen named storms, seven hurricanes, and three major hurricanes, but noted that the forecast had higher than normal uncertainty due to environmental factors.