Longer Hurricane Season?

July 24, 2023

LSU Climatologist Part of Team Recommending Changes to Hurricane Season 

BATON ROUGE - Hurricane season officially runs June 1 through November 30, but Louisiana State Climatologist and LSU professor Barry Keim and a group of researchers are finding hurricane season is becoming longer in duration, with the season beginning earlier and ending later.  

“Seven of the last eight years we’ve had named storms form before hurricane season officially began on June 1. We technically had a named storm in January of 2023,” said Keim, who is the Richard J. Russell Professor in the LSU Department of Geography & Anthropology.

Graphic showing the length of hurricane seasons since 1851

Season length in days, 1851–2022, measured from the start of the first named storm to the end of the last storm. Short-lived storms of < 2 days were excluded from the analysis. The red line in 1971 denotes the objectively identified breakpoint in season length (details in text). The dark orange line denotes the LOWESS regression curve. The shortest season was only 4 days, when in 1914, we only had one storm hence the season began when it was declared a tropical storm, and the season ended 4 days later the storm fizzled out.

– Courtesy: Barry Keim

A sea surface temperature of 80 degrees Fahrenheit is necessary to support the formation of a tropical storm or hurricane. Years with an early onset of hurricanes and busy hurricane seasons have sea surface temperatures well over the average. 

“Climate change is causing warmer sea surface temperatures for a longer period of time,” Keim said. “Warmer atmosphere and sea surface temperatures would result in a longer season because you’re over the 80-degree threshold to support a storm, so it makes logical sense that hurricane season would expand in both directions.”

Keim is working with researchers from LSU, the University of New Hampshire and Colorado State University, along with the Southern Climate Impact Planning Program, or SCIPP. SCIPP is a collaborative research program between LSU, the University of Oklahoma, LSU, Texas Sea Grant at Texas A&M University and Adaptation International that has helped communities in the southcentral U.S. plan for and mitigate the impacts of weather and climate since 2008. While Keim said they’re not the first to discover this early onset of recent hurricane seasons, they are the first to analyze it historically.  

“We have great records starting in 1970 because of the implementation of satellites, but prior to that, there is a drop-off in data quality. From World War II to the 1970s we had airplanes that collected data. Before World War II the quality of data drops again and we’re missing a lot of information about storms during that time, especially ocean-based storms. Before 1900 we’re relying on ship observation offshore,” Keim said.  

Based on their findings, Keim said the research is showing a need to change the official start of hurricane season. 

“It makes sense to start thinking about hurricane season beginning before June 1 to help residents and emergency officials plan and prepare for storms,” Keim said. “We need to wrap our heads around that hurricanes are arriving earlier in the season.”