Atlantic Hurricane Season Meets Forecasts for Above-Average Activity

The 2023 Atlantic hurricane season lived up to forecasts with above-average activity and was close to what was forecast by the Tropical Meteorology Project at Colorado State University (CSU), CSU researchers said in their 2023 forecast verification report.

The report noted that Colorado State's earliest seasonal forecast in early April somewhat underpredicted this season's activity. The 2023 Atlantic hurricane season ultimately saw 20 named storms, with 7 becoming hurricanes and 3 reaching major hurricane strength of Category 3 or greater.

The average Atlantic hurricane season has 14 named storms, 7 hurricanes, and 3 major hurricanes.

Three named storms and one hurricane made landfall in the continental United States this year, with Hurricane Idalia striking the Big Bend region of Florida as a Category 3 hurricane, the CSU report said. Idalia caused approximately $2.5 billion in damages and was responsible for five direct fatalities in the continental United States, the report said.

"The 2023 Atlantic hurricane season ended up above average. In general, our seasonal forecasts correctly anticipated these heightened levels of activity. Named storms and named storm days were well above their long-term averages, while accumulated cyclone energy was somewhat above normal," Phil Klotzbach, lead author of the forecast, said in a statement.

Accumulated cyclone energy is an integrated metric accounting for intensity and duration of storms, the CSU report said. This season's accumulated cyclone energy was approximately 120 percent of the 1991–2020 average, according to CSU.

The Colorado State researchers' initial 2023 hurricane season forecast in April predicted a slightly below-average hurricane season. It called for 13 named storms, including 6 hurricanes, 2 of which would be major hurricanes.

On June 1, the CSU team increased its forecast, calling for 15 named storms, including 7 hurricanes, 3 of which would be major hurricanes. A forecast update on July 6 called for 18 named storms, including 9 hurricanes, of which 4 would be major hurricanes. The Colorado State team's final update of the season on August 3 maintained that forecast.

The Colorado State team bases its annual hurricane forecasts on 70 years of historical data, including such factors as Atlantic sea surface temperatures and sea level pressures, levels of vertical wind shear (the change in wind direction and speed with height), El Niño (an anomalous warming of waters in the central and eastern tropical Pacific), and other factors, the CSU report said.