How Common are Atlantic Tropical Systems in May?

A tropical system could form near the Southeast coast of the United States later this week, which is several weeks ahead of the official start of the Atlantic hurricane season.

The Atlantic hurricane season officially runs from June 1 through Nov. 30.

Tropical systems during or prior to May and beyond November are uncommon, but they do occur.

According to Hurricane Expert Dan Kottlowski, "A tropical or subtropical storm forming in the Atlantic during May is not unprecedented."

The early and preseason tropical systems tend to form close to North and Central America.

The last time there was a named tropical system during May was in 2012.

According to Senior Meteorologist Kristina Pydynowski, "Tropical Storms Alberto and Beryl occurred during May of 2012."

A tropical depression formed during late May of 2009.

A tropical storm or hurricane in May or earlier in the year does not necessarily mean the upcoming season will be a busy one.

"There is no correlation between a tropical storm or hurricane prior to June and an above-average hurricane season," Kottlowski said.

The two tropical storms in May of 2012 were followed by 10 hurricanes and seven additional tropical storms later in the 2012 season with Hurricane Chris and Tropical Storm Debby during June.

However, the first tropical storm of the 2009 season did not occur until the middle of August that year.

"There were only three hurricanes and six tropical storms during the 2009 season," Pydynowski said.

On average, there are 12 named storms in the Atlantic each year with six becoming hurricanes, according to the NHC. will release its 2015 Atlantic hurricane season forecast during the middle of May.

In addition to the southern part of the East Coast, the northern Gulf states could be affected during June or earlier, due to warmer-than-average waters.

According to Chris Landsea, Ph.D., science and operations officer of the National Hurricane Center (NHC), there have been 20 tropical storms and four hurricanes during May, during the period from 1851 to 2014. A hurricane has never made landfall in the U.S. during May.

There has tended to be more named storms early in the season during recent decades, when compared to the entire 164 years of official record keeping.

The invention and use of weather satellites has contributed greatly to detection of budding tropical systems.

"We also have better tools for classifying tropical and subtropical systems now, compared to several decades ago when a number of systems were miss-diagnosed as non-tropical," Kottlowski said.

For example, during the middle of May 1916, a tropical storm formed near Cuba, traveled over part of the Southeastern coast of the U.S. and impacted Charleston, South Carolina. Had the system not ventured over land, it might have gone undetected.

While the realm of possibilities of a system later this week range from a weak non-tropical low pressure area to a hybrid system or perhaps a full-blown tropical storm, wind and rough surf will ramp up from northeastern Florida to southeastern Virginia.