With just one storm that made landfall in the United States, this year’s Atlantic hurricane season officially ended Saturday as the weakest since 1982.
Hurricanes need moist air to form, and the low number of Atlantic hurricanes was due in large part to dry air over the Gulf of Mexico, the Caribbean Sea and the tropical Atlantic Ocean, according to National Oceanic and Atmospheric Administration. The Atlantic hurricane season runs from June 1 to Nov. 30.
“This unexpectedly low activity is linked to an unpredictable atmospheric pattern that prevented the growth of storms by producing an exceptionally dry, sinking air and a strong vertical wind shear in much of the main hurricane formation region, which spans the tropical Atlantic Ocean and Caribbean Sea,” said Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center, in a statement.
This year’s season ranks as the sixth-least active since 1950, in terms of the collective strength and duration of tropical storms, and it was the third below-normal season since 1995, when the current high-activity era for Atlantic hurricanes began.
In an average year, there are 12 named storms, including six hurricanes and three major hurricanes. Though there were 13 named storms in 2013, only two – Ingrid and Humberto – developed into hurricanes, and neither became a major hurricane.
A tropical storm is a cyclone with sustained wind speeds of 39 to 73 mph. A storm becomes a hurricane when winds top 74 mph and a major hurricane when winds top 110 mph.