It's time to break out the Greek alphabet.

The 21th named storm of the Atlantic hurricane season formed on Friday, meaning forecasters have officially run out of planned names for storms this season. This is only the second time in recorded history that the Atlantic season has made it through the alphabet, and it's the earliest it has happened, as well.

The World Meteorological Organization lists 21 names for hurricanes and tropical storms at the start of each season, working its way through the alphabet but skipping Q, U, X, Y, and Z. Usually the hurricane season doesn't see enough intense storms to make it through that list, but the formation of Tropical Storm Wilfred on Friday marked the end of the line. Now, meteorologists will turn to the Greek alphabet. Subtropical storm Alpha already formed Friday and drifted into Portugal, and Tropical Storm Beta is currently swirling in the Gulf of Mexico. Wilfred, Alpha, and Beta also set a record by marking the first time three storms had formed in just six hours, Tomer Burg, a PhD candidate at the University of Oklahoma, told The Weather Channel.

The WMO has been naming storms since 1953, and it ran out of names for the first time in 2005. Wilma finished off the alphabet when it formed October 16, 2005, and eventually became a Category 5 storm. Five more storms followed it over the next two months. Kathryn Krawczyk