Karen was a subtropical storm in the North Atlantic Ocean late Thursday Eastern time, the National Hurricane Center said in its latest advisory.
Karen is the 11th named storm to form in the Atlantic in 2025.
The Atlantic hurricane season started on June 1 and runs through Nov. 30.
In late May, the National Oceanic and Atmospheric Administration, the parent agency of the National Weather Service, predicted that this would be an above-average season, with 13 to 19 named storms. In early August, a revised forecast from NOAA predicted 18 named storms for the season and said up to nine of them could become hurricanes.
Last year, there were 18 named storms, 11 of which became hurricanes. Five of those hurricanes became what the Hurricane Center calls "major," or Category 3, 4 or 5 on the Saffir-Simpson scale.
Hurricane Beryl was one of two Category 5 hurricanes last year, and it set records for the earliest point in a season that a storm had grown so big. In contrast, this year was one of the slowest starts to a season in 20 years.
Like the other most powerful storms last year, Beryl's quick intensity was a result of above-average ocean temperatures. But this year, in the main region where storms typically form, the ocean heat content -- the measure of thermal energy stored in the ocean that can fuel storms -- has been slightly below average in June.
Experts think it is probable that a major hurricane will make landfall in the U.S. this season. Climate experts have warned intense storms like these are more likely to occur, with more rapid intensification likely in a warming world.
Last year was also one of the most costly for hurricanes in the United States. Hurricanes Helene and Milton combined caused about $113 billion in damages and more than 250 deaths. This May, the Trump administration said it would no longer maintain a database of so-called billion-dollar disasters.
The Trump administration has slashed the number of employees at many of the agencies traditionally responsible for planning for and responding to natural disasters, including NOAA, the Weather Service and the Federal Emergency Management Agency.
Climate change is also affecting the amount of rain that storms can produce. In a warming world, the air can hold more moisture, which means a named storm can hold and produce more rainfall, like Hurricane Harvey did in Texas in 2017, when some areas received more than 40 inches of rain in less than 48 hours.
Researchers have also found that storms have slowed down, staying over areas for more extended periods, over the past few decades.