Tropical Storm Arlene, the first named storm of the 2017 Atlantic hurricane season, has developed in the north Atlantic Ocean. Arlene formed from Subtropical Depression One, which developed on Wednesday, and then became Tropical Depression One on Thursday morning.
Arlene is the first tropical storm in April to exist in the Atlantic Basin since Ana in 2003, which also formed on April 20, just a few hours earlier. It's also the farthest north a tropical storm has formed in the Atlantic so early in the season.
Prior to the beginning of the satellite era, which began in the 1970s, this type of storm was practically impossible to detect, according to the National Hurricane Center, so it is possible that others have occurred prior to 1970.
This is the third consecutive year a system has formed in the Atlantic before the official June 1 start of the hurricane season.