Atlantic Disturbance Could Become Unusual January Subtropical Storm

Quincy Vagell
Published: January 9,2016

The tropical Atlantic is usually in its winter slumber in January.
That may not be the case in 2016.
An area of low pressure is swirling in the western Atlantic Ocean east of Bermuda, producing a large area of tropical-storm force winds.
Although the storm does not currently have any tropical characteristics, the National Hurricane Center is monitoring it for possible development into a subtropical storm in the week ahead.

Latest Satellite

A subtropical storm displays features of both tropical and non-tropical systems, including a broad wind field, no cold or warm fronts, and generally low-topped thunderstorms displaced from the center of the system.
(MORE: Tropical vs. Subtropical Storms)
Despite the current disturbance having a sizable wind field with maximum winds in excess of 50 mph, and a well-defined center of circulation, its structure is comprised of a cold and warm front, as analyzed by buoy observations and satellite imagery.
As the system moves east-southeast across the open Atlantic, it may eventually begin to take on some subtropical characteristics.
Any future organization with this system would likely be in a hybrid nature, exhibiting characteristics of both a non-tropical and tropical low.

Possible Atlantic Subtropical Development

This low passed by Bermuda to the east, where winds had gusted to 59 mph early Friday afternoon. The farther south the system moves with time, the somewhat higher probability it may have for further organization, due to warmer sea-surface temperatures and lesser amounts of wind shear.
Should the system become a subtropical storm, it would be given the name "Alex."
Even if the low does not become subtropical, it is likely to remain a formidable system as it moves into the central Atlantic, possibly growing in size, producing large waves and strong winds. Some of this elevated surf is likely to reach the north and northeast coasts of The Bahamas, the Turks and Caicos, Puerto Rico, and Leeward Islands next week.

Early Season Tropical/Subtropical Storms

According to NOAA’s Hurricane Research Division, only two purely tropical storms have formed in the month of January in the north Atlantic since 1851. This does not include subtropical storms, although it appears that only two such storms have developed over the same time-frame in January. Also, a small handful of tropical systems have formed in December before dissipating in January, most recently including Tropical Storm Zeta in 2005-2006.
(MORE: 2005's Record-Breaking Tropical Season)
The Atlantic hurricane season officially runs from June 1 through November 30, but storms have, on an occasional basis, formed before and after that date.
Based on the long-term average, about once every 10 years, a tropical storm forms before June, most often in the month of May. This includes Tropical Storm Ana, which began as a subtropical storm in early May of 2015, eventually transitioning into a tropical system.
Likewise, roughly once every 10 years, a tropical storm has formed in the month of December. Post-season and pre-season tropical systems are usually relatively weak, in part due to cooler sea-surface temperatures in the winter and spring months, limiting the ability for such storms to intensify.

Other Recent Tropical Oddities

The north Atlantic is not alone when it comes to unusual winter tropical activity. Just a couple of weeks ago in late December, a tropical depression formed just north of the equator in the central Pacific. This system, Tropical Depression Nine-C, became the lowest latitude western hemisphere tropical cyclone on record, according to The Weather Channel’s hurricane specialist Michael Lowry.
Nine-C struggled to organize, later dissipating on January 1.

Latest Information on Pali

Almost as quickly as Nine-C weakened, another tropical disturbance started organizing in the central Pacific. This next system rapidly organized into Tropical Storm Pali, becoming the earliest tropical cyclone on record in either the central or eastern north Pacific.
The ongoing El Niño is likely a major factor in this recent tropical activity, especially in the Pacific, as the pattern is associated with significantly warmer than average sea-surface temperatures over the region.
While ocean temperatures may not generally be supportive for central Pacific tropical development in winter seasons without an El Niño, this year’s record-tying El Niño has supported more favorable conditions in the area.
(MORE: Could a Weakening El Niño Cause an Active Hurricane Season?)
It is difficult to say with any certainty if this recent and potential upcoming pre-season tropical activity will be a sign of things to come once hurricane season officially begins later this year.
Check back with weather.com for more information in the coming days.
MORE: Retired Atlantic Hurricanes and Tropical Storms