Rare December tropical storm could brew in Caribbean

Alex Sosnowski

Even though the Atlantic hurricane season has officially come to an end, additional tropical development is possible through the end of December. One disturbance over the Caribbean that is close to land could become the next Atlantic tropical depression or storm, according to AccuWeather meteorologists.

The Atlantic hurricane season officially extends from June 1 through Nov. 30, which is the period of time when tropical activity is mostly likely to happen in the basin, but like everything else in the weather, tropical systems can develop at any time given the right atmospheric conditions.

Tropical development has occurred during every month of the year in the Atlantic basin in the past, including December, although in most years, the winter and early spring months are quiet. Ten tropical storms that formed prior to December continued to churn in the basin into December in past years, and a total of 15 named storms formed during the last month of the year in the past, according to AccuWeather Meteorologist and Senior Weather Editor Jesse Ferrell.

A December storm hasn't occurred since an unnamed subtropical storm developed near the Azores on Dec. 5, 2013. Prior to that, Hurricane Olga churned across the basin during early December of 2008. Tropical Storm Zeta was named on Dec. 30 in the notoriously active and destructive 2005 hurricane season. It was only one of two storms that formed during the month of December and remained active into January. Hurricane Alice from 1954 was the other storm to stay alive into a new year.

An area of showers and thunderstorms AccuWeather meteorologists have been monitoring since last week is showing signs of life.

CLICK HERE FOR THE FREE ACCUWEATHER APP

Satellite images showed that the feature had a weak circulation Tuesday into Wednesday. There was another indication that potential development could occur, according to AccuWeather meteorologists. High-level clouds over top of the system were visible on satellite imagery -- a sign that air was rising near the disturbance's poorly-defined center.

This image was captured on midday Wednesday, Dec. 2, 2020. The disturbance does not look any better organized, when compared to 24 hours earlier, but conditions could change until the entire feature moves onshore in Central America on Thursday. (CIRA at Colorado State/GOES-East)

If a complete cyclonic wind pattern develops about a center, a depression could be dubbed. If a clear center is established and winds reach 39 mph or greater, a tropical storm would be born.

On Wednesday, part of the disturbance's weak circulation was over land, but much of the system remained offshore over the southwestern Caribbean. Until the system fully moves over land, the risk of development will continue.

"There is a short window in which this system in the southwest Caribbean has a chance to become a depression or even short-lived tropical storm before it moves over land over Central America Thursday afternoon," Dan Kottlowski, AccuWeather's top hurricane expert, said.

The next storm to develop will be given the name Kappa, the next letter in the Greek alphabet. The Greek alphabet first had to be utilized this season on Sept. 18, when a non-tropical system, similar to that of the feature currently northwest of Africa, evolved into a subtropical storm just offshore of Portugal. The designated list of names for the 2020 season had already been exhausted by that point.

This year's hurricane season has been not only hyperactive when compared to normal, but it has also been a record-breaker. The 30th storm of the season was Iota, which charged into Nicaragua on Nov. 16 as a Category 4 hurricane with 155-mph winds. However, since Iota dissipated over Central America, tropical activity has slowed considerably across the Atlantic basin.

By the middle of November, many of the prime development areas of the Atlantic, including the Gulf of Mexico and the western Atlantic, had been free of tropical activity due to strong winds aloft, colder air near the surface and dwindling moisture. By Dec. 1, the atmosphere across much of the Caribbean and all but the southeastern Atlantic had become too hostile to support tropical systems.

Waters are sufficiently warm to support a tropical disturbance in the southwestern Caribbean. Provided the disturbance remains offshore long enough and wind shear, which has been disrupting the system thus far, weakens, development could occur into Thursday.

"Frictional effects due to the proximity to land may inhibit development, but if the feature remains compact prior to pushing onshore, rapid organization and strengthening could take place," AccuWeather Senior Meteorologist Brett Anderson said.

Interests in Central America and the western part of the Caribbean are urged to closely monitor this feature this week.

Regardless of development or not, this slow-moving feature will drift westward and unleash drenching showers and locally gusty thunderstorms in Costa Rica, Panama and southern Nicaragua.

"This lower portion of Central America is at risk for dangerous flash flooding and mudslides from torrential rainfall over the rest of this week," Anderson said.

Central America has been hammered with multiple tropical systems during the latter part of this year's hurricane season. Major Hurricanes Eta and Iota struck within 15 miles of each other in northern Nicaragua during November, only about two weeks apart.

Beach and boating interests in the region should be aware of the risk of rough seas and surf that could quickly escalate to a more serious situation, should a tropical system ramp up to a depression and a storm.

If the southwestern Caribbean system becomes Tropical Storm Kappa and survives the trip westward into the Pacific, it would retain the name Kappa.

This wouldn't be the only storm to cross over to the other basin this season. The first named system in the eastern Pacific this year was Amanda, and it moved onshore in Central America and diminished. However, leftover moisture helped to give birth to Cristobal in the southwestern Gulf, which went on to strike the southern United States.

There is a chance the current Caribbean disturbance, if it develops, could be the last tropical system of the season, although AccuWeather forecasters explained that there will be some risk of development across part of the Caribbean and the central and southeastern part of the North Atlantic in the coming weeks.

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.