And Henri formed on Aug. 16 as a tropical storm off the East Coast of the United States. It strengthened into a Category 1 hurricane but was downgraded before making landfall in Rhode Island, sparing the region the worst of what had been predicted. It thrashed the Northeast with fierce winds and torrential rain, knocking out power to more than 140,000 households from New Jersey to Maine. Some communities in Connecticut were evacuated and rainfall records in New York City were shattered.
The links between hurricanes and climate change are becoming more apparent. A warming planet can expect to see stronger hurricanes over time, and a higher incidence of the most powerful storms — though the overall number of storms could drop, because factors like stronger wind shear could keep weaker storms from forming.
Hurricanes are also becoming wetter because of more water vapor in the warmer atmosphere; scientists have suggested storms like Hurricane Harvey in 2017 produced far more rain than they would have without the human effects on climate. Also, rising sea levels are contributing to higher storm surge — the most destructive element of tropical cyclones.
A major United Nations climate report released in August warned that nations have delayed curbing their fossil-fuel emissions for so long that they can no longer stop global warming from intensifying over the next 30 years, leading to more frequent life-threatening heat waves and severe droughts. Tropical cyclones have likely become more intense over the past 40 years, the report said, a shift that cannot be explained by natural variability alone.
Ana became the first named storm of the season on May 23, making this the seventh year in a row that a named storm developed in the Atlantic before the official start of the season on June 1.
In May, scientists with the National Oceanic and Atmospheric Administration forecast that there would be 13 to 20 named storms this year, six to 10 of which would be hurricanes, and three to five major hurricanes of Category 3 or higher in the Atlantic. In early August, in a midseason update to the forecast, they continued to warn that this year’s hurricane season will be an above average one, suggesting a busy end to the season.
Matthew Rosencrans, of the National Oceanic and Atmospheric Administration, said that an updated forecast suggested that there would be 15 to 21 named storms, including seven to 10 hurricanes, by the end of the season on Nov. 30. Ida is the ninth named storm of 2021.