Sam, the fourth named storm to form in less than a week, was expected to strengthen into a “major” hurricane by the weekend.
Tropical Storm Sam strengthened into a hurricane early Friday and was expected to intensify rapidly as it moved west across the Atlantic Ocean, forecasters said.
The hurricane was more than 1,400 miles east of the eastern Caribbean as of 5 a.m. Eastern time, moving west at 15 miles per hour with maximum sustained winds of 75 m.p.h., according to the National Hurricane Center.
Sam, which formed on Thursday in the central Atlantic, is the fourth named storm to develop in less than a week and the 18th overall in a busy 2021 hurricane season.
The hurricane was not projected to immediately affect land, and no coastal watches or warnings were in effect. But forecasters said it would likely strengthen into a “major” hurricane by Friday night or Saturday morning. The Saffir-Simpson scale classifies major hurricanes as Category 3 or higher, with maximum sustained winds above 110 m.p.h.
It has been a dizzying couple of months for meteorologists as the arrival of peak hurricane season — August through November — led to a run of named storms that formed in quick succession, bringing stormy weather, flooding and damaging winds to parts of the United States and the Caribbean.
The links between hurricanes and climate change are becoming more apparent. A warming planet can expect 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.
Ana became the first named storm of the 2021 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, including three to five major hurricanes of Category 3 or higher in the Atlantic.
NOAA updated its forecast in early August, predicting 15 to 21 named storms, including seven to 10 hurricanes, by the end of the season on Nov. 30. Sam is the 18th named storm to form this year.
Last year, there were 30 named storms, including six major hurricanes, forcing meteorologists to exhaust the alphabet for the second time and move to using Greek letters.
It was the most named storms on record, surpassing the 28 from 2005, and the second-highest number of hurricanes.