US prepares for tropical storm Sara after it makes landfall in Central America

As the third named storm to emerge during November, Tropical Storm Sara serves as a reminder that the Atlantic hurricane season hasn’t quite ended.

Sara formed in the western Caribbean Sea before making landfall Thursday on the northern coast of Honduras, dumping torrential rains in a slow weekend crawl across parts of Central America. The National Hurricane Centre in Miami said the storm could dump up to 40 inches (101.6 centimetres) of rain in some areas and is expected to move over Belize Sunday before dissipating over the Yucatan Peninsula early Monday.

Sara follows two other named storms so far this month. Tropical Storm Patty brought heavy rain to the Azores and dissipated without striking land. Then Hurricane Rafael struck Jamaica and the Cayman Islands before tearing across Cuba as a Category 3 storm.

That has made for an unusually active final month for the hurricane season, when forecasters typically see a single named storm every year or two. And the 2024 season still has two weeks to go. Here are some things to know about November hurricanes.

WHY DOES HURRICANE SEASON TYPICALLY WIND DOWN IN NOVEMBER?
The hurricane season for storms in the Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico officially runs from June 1 to November 30. Though named storms have been known to form before and after that six-month period, hurricane season reflects the months when weather conditions are more favourable for producing tropical storms and hurricanes.

Ocean temperatures must reach at least 79 degrees Fahrenheit (26 Celsius) to fuel hurricanes. Hurricane season is also when the upper atmosphere tends to have reduced wind shear, or changes in wind speed and direction that tear hurricanes apart. Those hostile winds tend to ramp up later into the fall, making it more difficult for November storms to form, said Levi Silvers, a hurricane researcher at Colorado State University.

”We have the water temperatures to allow for these storms to form,” Silvers said. “But it’s increasingly unlikely we’re going to get the conducive winds.”

HOW UNUSUAL ARE HURRICANES IN NOVEMBER?
Based on the 30-year period from 1991 to 2020, November typically sees one tropical storm every year or two. Storms that strengthen into hurricanes are rarer during the season’s final month, with one occurring generally every two years, according to the hurricane centre.

Since 1851, a total of 125 tropical storms have been recorded during November, said Brian McNoldy, a hurricane researcher at the University of Miami. About half of those storms, 63, went on to become hurricanes. And 12 strengthened into major hurricanes with winds above 110 mph (177 kph).

Rafael earlier this month forced the evacuation of 283,000 people in Cuba and destroyed 460 homes. It was the Atlantic basin’s first November hurricane since 2022, when the season wrapped up with three storms. One of them, Hurricane Nicole, became the first November hurricane to make landfall in Florida since 1985.

Only two other November hurricanes are known to have struck the US, in 1861 and in 1935, according to the National Oceanic and Atmospheric Administration.

WHAT ARE SOME NOTABLE NOVEMBER STORMS?
Since 1953, there have been seven November hurricanes devastating enough to have their names retired, McNoldy said.

The last ones were Hurricanes Eta and Iota, both Category 4 storms when they smashed into the Caribbean coast of Nicaragua two weeks apart in November 2020. The back-to-back hurricanes were blamed for a combined 239 deaths and $8.2 billion in damage across Central America.

They struck at the end of the most active hurricane season on record with 30 named storms. The busy 2020 season exhausted the year’s alphabetical list of storm names by mid-September. Later storms, including Eta and Iota, were identified using Greek letters.

Other destructive November hurricanes that had their names retired were Otto in 2016, Paloma in 2008, Noel in 2007, Michelle in 2001 and Lenny in 1999, according to McNoldy.

IS CLIMATE CHANGE EXTENDING THE THREAT OF HURRICANES?

There have been 18 named storms since 2000 that formed outside the official hurricane season, either before June or after November. One of them, Hurricane Alex, spun up on January 12, 2016. Does that mean climate change caused by humans is lengthening the hurricane season?

“The role I could see climate change playing in extending the bounds of the traditional hurricane season is the warming ocean,” said McNoldy, noting that sea surface temperatures in the Gulf of Mexico and the Caribbean have remained unusually warm into mid-November.

However, scientists still have unsettled questions regarding what influence climate change may have on seasonal wind shear patterns that tend to keep tropical cyclones at bay outside the official hurricane season, Silvers said.

“The idea that we’re seeing more hurricanes with climate change is still pretty controversial,” Silvers said. “I think what seems clear is we’ve had a lot of high-impact hurricanes and rapidly intensifying hurricanes. It could be that, with climate change, you don’t get more hurricanes, but you get stronger hurricanes.”