Subtropical storm Alex: Is climate change to blame for rare January hurricanes?

A subtropical storm is surprising meteorologists as it forms early in January, nearly six months ahead of the typical tropical storm season.

Subtropical storm Alex is building over the Atlantic Ocean and is gaining strength as it approaches the Azores Islands, a chain of nine major islands owned by Portugal. By Thursday morning, Alex had produced sustained winds of 70 mph.

The Atlantic hurricane season officially runs from June through November. The first named storm doesn't typically appear until July. However, 2016 is shaping up to be a very different year, with named storms forming near simultaneously in both the Atlantic and the Pacific Oceans in January. (Hurricane Pali, the first named storm of the year, began forming in the Pacific last week.)

“Alex is the first tropical or subtropical storm to form in January since an unnamed system did so in 1978, and is only the fourth known to form in this month in the historical record that begins in 1851,” the National Hurricane Center wrote in its forecast discussion.

A tropical storm forms before June, usually in the month of May, about once every 10 years, according to calculation completed by The Weather Channel based on the longer-term average. Similarly, about once every 10 years, a tropical storm forms in December. These rare storms are typically less intense and weaker due to cooler water temperatures.

This year, however, Atlantic water temperatures are unusually warm, about 2-4 degrees Fahrenheit above average, partly due to El Niño, but also as a result of climate change, as Jeff Masters, founder of Weather Underground and a former hurricane chaser reports:

Global warming made Alex's formation much more likely to occur, and the same can be said for the formation of Hurricane Pali in the Central Pacific. To get both of these storms simultaneously in January is something that would have had a vanishingly small probability more than 30 years ago, before global warming really began to ramp up.

Alex, which is showing maximum wind speeds of 70 mph Thursday morning, has an intensity of 60 knots, according to the National Hurricane Center. Alex is centered about 560 miles south-southwest of the Azores and is approaching the island chain at a rate of 18 mph.

The storm will likely reach the Azores Thursday night and remain through Friday. Three to 5 inches of rain can be expected, complimented by flash floods, mudslides, and gale-force winds.

As of early Thursday morning, no tropical storm warning has been issued. Alex has the potential to transform back into a non-tropical low-pressure system by the time it reaches the Azores, according to The Weather Channel.

Alex’s current classification as a subtropical storm means it exhibits characteristics of both tropical and non-tropical storms. That includes, “a broad wind field, no cold or warm fronts, and generally low-topped thunderstorms displaced from the center of the system,” according to The Weather Channel. Subtropical storms also have the potential to form into fully tropical storms.

This report includes material from The Associated Press and Reuters.