By Mary Gilbert, CNN Meteorologist
(CNN) — Hurricane Lee has strengthened into a major Category 4 storm with maximum sustained wind speeds of 130 mph, according to the 5 p.m. EDT advisory from the National Hurricane Center.
“Additional strengthening is expected tonight. Fluctuations in intensity are expected after that, but Lee is forecast to remain a powerful major hurricane well into next week,” the center said.
Lee, which was a Category 1 storm earlier Thursday, has been intensifying with exceptional speed in the warm waters of the Atlantic Ocean, strengthening by 50 mph in the last 12 hours.
The hurricane is located about 780 miles east of the northern Leeward Islands, the hurricane center said in its 5 p.m. update.
The storm will likely reach its peak intensity this weekend and is still expected to be a dangerous hurricane over the southwestern Atlantic early next week, though it’s too soon to know whether this system will directly impact the US mainland.
Dangerous surf and rip currents will spread across the northern Caribbean on Friday and begin affecting the United States on Sunday, the center said.
There is increasing confidence that the center of Lee will pass to the north of the northern Leeward Islands, the Virgin Islands and Puerto Rico this weekend and into early next week. There is a potential for tropical storm conditions to occur on some of these islands over the weekend.
The swells are expected to reach portions of the Lesser Antilles on Friday, and the British and US Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda this weekend.
Even more rapid intensification is expected because the forecast track takes the hurricane across some of the warmest waters in the Atlantic Ocean and through relatively calm upper-level winds – ripe conditions for a hurricane to grow more fierce.
“All the ingredients are in place for the storm to really intensify,” Jason Dunion, director of NOAA’s Hurricane Field Program, told CNN.
Lee’s winds are expected to peak at 160 mph, or Category 5-strength, Friday night as it approaches the eastern Caribbean and is still expected to be a dangerous hurricane over the southwestern Atlantic early next week.
Also Thursday, a tropical depression in the eastern Atlantic strengthened into Tropical Storm Margot, just a few hundred miles west of the Cabo Verde Islands, the center said. Margot currently has winds of 40 mph and steady strengthening is expected – the center is forecasting Margot to become a hurricane over the weekend. The forecast track shows the storm turning to the north over the central Atlantic early next week, but it is not expected to threaten any land areas as of Thursday.
The waters in the Atlantic are not quite as warm as the steamy conditions in the Gulf of Mexico, which gave rise to Hurricane Idalia last week. However, sea-surface temperatures across the portion of the Atlantic Ocean that Lee is set to track through are still a staggering 2 degrees Celsius (3.6 degrees Fahrenheit) above normal after rising to “far above record levels” this summer, according to David Zierden, Florida’s state climatologist.
“To get to Category 4 or 5 intensity the environment has to be nearly perfect, which it looks like is the forecast for Lee,” Zierden told CNN.
Lee’s maximum forecast intensity of 150 mph is equivalent to the strongest storm in the Atlantic basin this season – Hurricane Franklin – and stronger than any storm so far in the eastern Pacific. If Lee tops 150 mph, it will be the most powerful hurricane to roam either basin this year.
That forecast is also just 7 mph shy of Category 5.
“This storm definitely has the potential to be a Category 5,” Dunion said, adding that nothing in Lee’s forecast path is expected to hinder the storm’s development leading up to the weekend.
The last Category 5 hurricane to roam the Atlantic basin was 2022’s Hurricane Ian. Before that, 2019’s Dorian and Lorenzo were the most recent hurricanes to achieve the feat. Only 39 Category 5 hurricanes have occurred since 1924, according to data from NOAA.
Any shifts along Lee’s track as it nears the Leeward Islands would increase the threat of more direct impacts like heavy rainfall and strong winds. Anyone in the eastern Caribbean – including the Leeward Islands, Puerto Rico and Hispaniola – as well as the Bahamas will need to keep a close eye on the forecast headed into the weekend.
Lee is ramping up in intensity as the peak of the Atlantic hurricane season approaches. Sunday, September 10, is the climatological peak of Atlantic hurricane season, when the basin is at its busiest on average. A flurry of tropical activity surrounding this date is not out of the ordinary, but it can turn hazardous fast.
The 2023 Atlantic season has already been busy: It is tracking above average for a number of different metrics including number of named storms, number of hurricanes and number of major hurricanes, according to Philip Klotzbach, a research scientist at Colorado State University.
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CNN’s Robert Shackelford, Monica Garrett and Nouran Salahieh contributed to this report.