Sam, a Category 1 storm, forecast to rapidly intensify into next major hurricane

·4 min read

Hurricane Sam developed over the open waters of the eastern Atlantic on Friday morning after becoming the 18th named storm of the 2021 hurricane season on Thursday morning. AccuWeather forecasters expect Sam to strengthen further into a major hurricane prior to approaching the islands of the northern Caribbean next week.

Sam was located 1,365 miles to the east-southeast of the northern Leeward Islands, packing winds of 75 mph, and was moving toward the west at 14 mph as of Friday midday.

"Intensification is expected into the weekend," AccuWeather Senior Meteorologist Rob Miller said.

The strengthening system is expected to take a west to west-northwest path across the central Atlantic through this weekend. Beyond that, AccuWeather forecasters say there is a range of possibilities as to where Sam may track across the basin, but they urge interests from Bermuda to the Bahamas, the East Coast of the United States and Atlantic Canada to monitor the system for potential impact.

Hurricane Sam is seen more than 1,400 miles away from the Leeward Islands on Friday, Sept. 24, 2021. (Photo/AccuWeather RealVue™ satellite)

"Sam could approach the northern Leeward Islands by Tuesday of next week as a major hurricane," Miller said, meaning the storm's maximum sustained winds could be at least 111 mph -- the threshold for a Category 3 hurricane.

Beginning this weekend, swells propagating outward from the center of the storm will produce rough surf along the eastern shores of both the Leeward and Windward islands. Sam will also stir up rough seas for any ships navigating the open Atlantic, and forecasters are urging anyone involved with maritime operations to monitor the situation as large waves could be a threat even at a great distance from the storm's center.

A zone of strong winds in the middle levels of the atmosphere was still present over the Caribbean and the central Atlantic. This phenomenon, known as wind shear, can prevent tropical systems from strengthening, under certain conditions.

"Wind shear is expected to decrease around the zone of the Atlantic where Sam is tracking toward this weekend and that should not be a deterrent for strengthening," AccuWeather Meteorologist Randy Adkins said. But, it's possible the system will encounter more disruptive wind shear near the Bahamas and Cuba next week, if Sam manages to navigate that far to the west.

"What happens with Sam over the next two to three days will determine, in part, whether or not Sam becomes a threat for the Leeward Islands and Puerto Rico," Adkins said.

"The faster that Sam strengthens over the next few days the farther north it is likely to track," Adkins added.

On the other hand, if the tropical system were to strengthen over the open ocean, then it may be more prone to turning northward due to the physical forces exerted by the rotation of the Earth.

The track of the tropical system beyond it passing near the northern islands of the Caribbean is less certain. One scenario would allow the system to turn northward as westerly winds strengthen near North America. In that case, it may become a direct concern for Bermuda or perhaps Atlantic Canada during early October.

However, there is potential for the system to continue to track to the west as it nears the islands of the northern Caribbean and the Bahamas. In that scenario, it could wander close to the East Coast of the U.S.

Teresa, Victor and Wanda are the only names remaining on the list now that Sam has been named.

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Once the list has been exhausted, and that is likely to happen this season, storms will be named using a supplemental list prepared by the World Meteorological Organization. Adria, Braylen and Caridad are the first three names on the list, which is being used for the first time after the Greek alphabet was retired earlier this year. The Greek alphabet had been used to name storms during only two Atlantic seasons: the hyperactive 2020 and 2005 hurricane seasons.

Two other tropical systems, tropical depressions Peter and Rose, have dissipated over the Atlantic Ocean. Peter fell apart north of Puerto Rico on Wednesday night. By Thursday morning, Tropical Depression Rose had dissipated over the central Atlantic.

In addition to Hurricane Sam over the eastern Atlantic, there is the potential for Odette, a storm that first formed off the East Coast, to regenerate over the open waters of the north Atlantic.

2021 Atlantic Tropical Storm Supplemental List

Supplemental names for Atlantic tropical storms should the original list be exhausted.

"Odette has a better than 50/50 chance of regaining tropical storm status, although due to dry air that has infiltrated this strengthening circulation, it would likely be subtropical in nature," Adkins said. A subtropical storm has both tropical and non-tropical characteristics. Even if it does develop further, it will meander around the North Atlantic and could even loop around in the coming days.

Hurricane season is still far from over, with more than two months left. AccuWeather's tropical weather team is expecting up to 25 named storms this season, which officially ends Nov. 30.

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