A hurricane is a Category 5 hurricane with maximum sustained winds of 185 mph and maximum sustained rainfall of 20 inches.
Its maximum sustained wind speed is 275 mph and rainfall is 3 inches.
Satellite images of the storm show the storm grew to a Category 4 hurricane in a matter of hours.
The storm grew as much as 10 feet in size over a period of about five hours, with its winds reaching 280 mph.
The storm is located just off the coast of the United States in the Gulf of Mexico and has been centered in the northern part of the Atlantic Ocean, according to a statement from the National Hurricane Center.
The storm was last active in February 2017.
It was reported to have moved westward toward the United Kingdom on Thursday.
The U.K. government tweeted that it was “monitoring the situation”.
In the U.S., Tropical Storm Katrina has moved northward over the east coast of North America and is expected to strengthen to a category 5 hurricane on Friday.