Can hurricanes form outside of the official tropical season in the Atlantic?
By Brian Lada, AccuWeather meteorologist and staff writer
The Atlantic hurricane season draws to a close on Nov. 30, but this does not always mean that the threat of tropical systems is over until the following season.
The Atlantic hurricane season officially begins on June 1 and lasts until Nov. 30. This span of time is when weather conditions are most favorable for tropical development.
However, under the right conditions, tropical systems can take shape outside of the traditional hurricane season.
According to National Hurricane Center records, dating back to 1851, at least one named tropical storm or hurricane has occurred during every month of the year in the Atlantic. However, off-season systems are not common and do not develop every year.
“If there’s going to be early season development, it’s most likely going to take place across the south-central Atlantic well east of Bermuda,” AccuWeather Hurricane Expert Dan Kottlowski said.
“The reason for that is that’s where a lot of upper-level storms develop, and if they can drift far enough south into the warmer water, they may take on a sub-tropical, or maybe even a tropical, appearance,” Kottlowski said.
A subtropical storm is a type of hybrid storm, showing both tropical and non-tropical characteristics, and can eventually transition into a named tropical storm or hurricane.
This was the case for Arlene in the 2017 Atlantic hurricane season. The system first became a subtropical depression on April 19, 2017, eventually becoming Tropical Storm Arlene over the open waters of the Atlantic.
Why the 2017 Atlantic hurricane season ranks among the top 7 most intense ever recorded
AccuWeather delivers aid in Puerto Rico, finds rays of hope and resiliency
AccuWeather hurricane center
Many of the tropical systems that develop between December and May are similar to Arlene, spending their lives spinning over the Atlantic Ocean rather than the Caribbean Sea or Gulf of Mexico, closer to land.
“It would be very, very rare for something to development in the Gulf of Mexico as we go into December,” Kottlowski said.
This is due to strong upper-level winds, called the westerlies, shifting over the Gulf of Mexico and the Caribbean Sea during winter. These disruptive winds are usually entrenched over the region during the winter months, preventing disturbances from becoming organized into tropical systems.
These winds begin to weaken and shift northward later in the spring, making May the most common month for off-season tropical development in the Atlantic basin.
When tropical systems do develop between December and May, they tend to remain weak with a majority of systems never reaching hurricane status.
Since records began, there have only ever been two hurricanes that have reached Category 2 status outside of the tropical season, and none that have become a major, Category 3 or higher, hurricane.
Hurricane Amanda was one of the strongest off-season storms recorded in the Atlantic Basin, becoming a Category 2 hurricane with winds of 105 mph. This was also one of the few early-season storms to impact the United States directly, making landfall in Florida on May 28, 1863.
Comments that don't add to the conversation may be automatically or manually removed by Facebook or AccuWeather. Profanity, personal attacks, and spam will not be tolerated.
More Weather News
Weather News - December 18, 2018, 10:36:44 PM EST
A powerful storm plowed into Washington state on Tuesday afternoon, bringing a tornado, high winds, heavy rain and heavy snow.
Weather News - December 18, 2018, 2:20:05 PM EST
A major storm that will plow into the eastern half of the United States late this week could throw a wrench into plans for early holiday travelers as well as holiday shipping.
Weather News - December 18, 2018, 10:14:22 PM EST
Expect more storms with heavy rain, heavy mountain snow and rough seas to lash the West Coast of the United States into Christmas Day.
Weather News - December 18, 2018, 10:48:58 AM EST
A slow-moving storm system will bring daily downpours to parts of the Middle East through Thursday.
As wildfires rage and threaten to destroy everything in their paths, we often hear that they are contained by a certain percentage.
Weather News - December 18, 2018, 2:42:41 PM EST
Following far-reaching snowstorms from November and early December, a lack of Arctic air will generally limit the chances of a white Christmas to the northern tier states and the mountains of the West for Dec. 25, 2018.
Fighting wildfires costs the United States billions of dollars each year. It turns out that humans have ignited a significant chunk of these destructive blazes.
Weather News - December 18, 2018, 9:24:30 AM EST
A stormy weather pattern is expected to persist across much of Europe through the Christmas holiday.