How rare are December tropical systems?

JACKSONVILLE, Fla. -- – Hurricane season may have come to a close, but there could be another tropical system in December.

The National Hurricane Center continues to watch an area in the open Atlantic, which has a medium chance of becoming a subtropical or tropical storm by late week.

So, how often do we December tropical systems?

In recorded history, only 28 systems became subtropical or tropical cyclones in December in the Atlantic basin.

The most recent December system was in 2013. However, it was never named and was defined as a subtropical storm in a later reanalysis of the season.

The last named storm in December was Olga in 2007.

Olga started as a subtropical storm near Puerto Rico, and then pushed eastward.

The system became a tropical storm and impacted Puerto Rico, the Dominican Republic and Haiti. 40 deaths were reported from Olga.

The December lull

It’s much harder for a tropical system to form because the atmosphere is vastly different in the tropical Atlantic compared to the peak months of September and October.

Cold fronts can now reach deep into the Caribbean and open Atlantic, which brings cool, dry air into that region.

Another major factor is water temperatures.

Water temps across all of the Atlantic are significantly cooler than in September. These water temps will continue to cool as we move forward into winter.

Most systems in December form similar to the current area in the open Atlantic - an area of low pressure in the open Atlantic that attempts to organize into a subtropical storm.

The Reason for the Season

If this area does become a named storm, it would be “outside” the Atlantic hurricane season, which runs from June 1 - November 30.

This is defined as “hurricane season” as the vast majority of tropical systems occur during these six months.

Outside of the season, December is the second most-likely month to see tropical activity.

May is the busiest outside hurricane season with 52 recorded storms. 2022 was the first year since 2014 a May storm did not form.

There have been preliminary discussions about starting the hurricane season in mid-May, and the National Hurricane Center does issue updates starting on May 15.

The good news is the system will stay well away from land, so if we end up with a named storm, it will simply be a system for the history books.