The 2021 Atlantic hurricane season was the third most active on record and the sixth consecutive year of above-average hurricane activity. Still, the overall season was mostly in line with the updated 30-year average, according to experts from AIR Worldwide.
However, the season did reveal some “unsettling” trends, said Jeffrey Strong, research scientist in the Hurricane Hazard group at AIR, during a webinar on the 2021 U.S. Hurricane Season Review.
The season saw 21 named storms and seven hurricanes, four of which reached major hurricane status of Cat 3 or higher on the Saffir-Simpson scale. Two hurricanes made U.S. landfall in 2021: Hurricane Ida, which arrived in Louisiana on Aug. 30 as a Cat 4 storm, and Hurricane Nicholas, which hit southeast Texas on Sept. 14 as a Cat 1.
Strong said that comparing the previous 30-year average (1981-2010) to the updated one (1991-2020) shows an “alarming trend of increased activity across the North Atlantic Basin. This trend will certainly be bolstered by the previous two years of above-average activity.”
Strong highlighted several hurricanes for their notable activity:
Hurricane Grace made landfall in Jamaica on Aug. 17 as a tropical storm before strengthening into a Cat 1 hurricane by late in the day on Aug. 18. Grace then made landfall near Tulum, Mexico on Aug. 19 before slowly degrading back to tropical storm strength. However, another bout of rapid intensification caused the storm to peak at Cat 3 just before landfall in the Mexican state of Veracruz on Aug. 21. Grace rapidly weakened over Mexico before dissipating later that day.
Strong noted, “One unsettling trend—and a storyline going forward—that major Hurricane Grace highlights is the increased occurrence of rapid intensification events during a hurricane season.” He defined rapid intensification “as a storm which intensifies by at least 30 knots in a given 24-hour period.” He said that preliminary data reveals the 2021 hurricane season saw eight rapid intensification events spread across six storms.
Hurricane Larry achieved hurricane status as a Cat 1 on Sept. 2 before intensifying to a Cat 3 two days later. The storm made landfall in Newfoundland on Sept. 11 as a Cat 1 before becoming an extratropical cyclone. Hurricane Sam, meanwhile, strengthened into a hurricane on Sept. 24 and reached Cat 4 by Sept. 25. The storm weakened and re-strengthened several times before finally transitioning to an extratropical cyclone on Oct. 5. Strong said the two storms were remarkable due to the length of time each spent at hurricane status. Both storms quickly reached and maintained their peak intensity for a prolonged period.
Hurricane Henri became a Cat 1 on Aug. 21 but weakened back to a tropical storm before making landfall in Rhode Island with maximum sustained winds of 60 mph. Strong said the storm is notable because its slow forward speed at landfall and predecessor rains dumped more than eight inches of rain in parts of New Jersey and New York. He noted that the rain gauges in Central Park measured the highest one-hour total rainfall going back to 1943.
Hurricane Ida was the most destructive storm of the 2021 season. After achieving tropical storm status on Aug. 26, Ida intensified into a Cat 1 hurricane before making two landfalls in Cuba on Aug. 27. The hurricane then underwent another bout of rapid intensification into a Cat 4 by Aug. 29, with peak intensity of sustained 150 mph winds, and made landfall near Port Fourchon, La. Ida weakened to a tropical depression on Aug. 30. Hurricane Ida maintained its landfall intensity longer than most other notable storms and produced a record-breaking amount of rainfall, Strong said, adding that this is an unfortunate expectation of climate change.
More Mitigation Efforts Needed
Hurricane Ida also proved the importance of mitigation efforts, said Tim Johnson, senior engineer at AIR, who also spoke during the webinar. While New Orleans benefitted from upgraded post-Katrina buildings codes and the investment in the levee system, communities along the bayou were not so lucky. Johnson noted that many of these small communities rely entirely on the integrity of their levees, some of which were breached by Hurricane Ida.
Hurricane Ida’s landfall near Port Fourchon also had major ramifications to the oil operations in the Gulf of Mexico, as the port is a critical facility. The damage caused large reductions in oil production, Johnson said, adding that two weeks later production levels were only at 23 percent of pre-Ida levels.
The hurricane was also notable for its impact on the energy grid. Louisiana reported over a million outages, with some of the most impacted areas experiencing extended power delays for weeks. Reports say Hurricane Ida damaged more than 30,000 utility poles—almost twice as many as Katrina.
“Power restoration is one of the most critical elements in event recovery,” said Johnson. “Without power, many other restoration projects are delayed. Any delays can increase the potential for higher losses due to loss of use or mold growth, which may require additional resources to restore.”
*Top photo: Homes, businesses and roads are flooded in the aftermath of Hurricane Ida in LaPlace, La., Aug. 31, 2021. (AP Photo/Gerald Herbert)