Hurricane Sam spins in the Atlantic as a Category 3; Bermuda in the 'cone of uncertainty'

Sam will pass well to the northeast of the Leeward Islands, then curl northward in the direction of Bermuda

Hurricane Sam is churning through the tropical Atlantic Ocean as a Category 3 hurricane and will curl northwestward before reaching the Leeward Islands.

Sam rapidly intensified over the weekend, becoming the fourth major hurricane – Category 3 or higher – of the 2021 Atlantic hurricane season. The storm's maximum sustained winds increased from 85 mph to 140 mph in the 24-hour period ending Saturday at 5 p.m. Eastern time. That's a 55-mph increase, far exceeding the criteria for rapid intensification: 35 mph in 24 hours or less.

According to the National Hurricane Center, Sam peaked in intensity Sunday evening when its maximum sustained winds reached 155 mph, just shy of Category 5 intensity (157 mph).

Sam's intensity has ticked down a bit as of Monday, but it remains a powerful Category 3 hurricane more than 700 miles east-southeast of the northern Leeward Islands.

The NHC said fluctuations in intensity are possible over the next few days, but Sam is forecast to remain a major hurricane through at least Thursday night.

Hurricane Sam is moving northwestward at about 8 mph, and this general track is expected to continue into midweek, with an increase in forward speed expected on Thursday. A turn to the north is then expected on Friday.

On this forecast track, Sam will pass well to the northeast of the northern Leeward Islands Wednesday and Thursday, then curl northward in the direction of Bermuda by this weekend.

Although Bermuda is included in the hurricane's "cone of uncertainty," the center of the storm is likely to pass to the east of the archipelago. However, the storm's effects will extend far from its center, so some impacts from rain, wind and storm surge are possible in Bermuda this weekend.

Additionally, swells generated by Sam will reach the Lesser Antilles on Monday and will impact these islands for the next several days. Swells are then expected to reach Bermuda and the Bahamas mid- to late week, eventually spreading to the East Coast of the United States late this week. These swells could cause life-threatening surf and rip current conditions, the NHC warned.

Last Thursday (Sept. 23), Sam became the 18th named storm of the 2021 Atlantic hurricane season. That made it the second-earliest "S" storm on record in the Atlantic, behind only Sally in 2020, according to a tweet by NHC hurricane specialist Philippe Papin.

In addition to Hurricane Sam, three other systems are also being monitored for possible tropical development in the Atlantic this week.