The 2015 Hurricane Season Gets Underway

Tropical Storm Ana (May 9, 2015)  Source: NASA

Today is the first day of the 2015 hurricane season in the Atlantic Ocean.  An average hurricane season features 10 named tropical storms, 6 hurricanes and 2 major hurricanes.  A system becomes a tropical storm when sustained winds around the center of the storm reach 39 mph.  A tropical storm becomes a hurricane when sustained winds reach 74 mph and a hurricane is classified as “major” once sustained winds reach at least 111 mph and it becomes a Category 3 on the “Saffir-Simpson” Hurricane Intensity Scale.  A system is given a name when it becomes a tropical storm.

NOAA recently released their forecast for the 2015 hurricane season.  They predicted 6 to 11 tropical storms, of which 3 to 6 will become hurricanes and 2 of those will become major hurricanes.  That would make 2015 an average or slightly below average season.  Tropical meteorologists at Colorado State University are also calling for a below average hurricane season in the Atlantic Ocean with only 7 tropical storms, 3 hurricanes and 1 major hurricane. 

NOAA cites the presence of El Nino as a primary factor for expecting an average or quieter than average season.  “El Nino” refers to the unusual warming of the tropical East Pacific Ocean off the west coast of Mexico and Central America.  This helps create unfavorable conditions in the tropical Atlantic including increased wind shear – or wind speeds that change direction with height. 

A quieter than average hurricane season doesn’t necessarily mean it won’t be a damaging or deadly hurricane season.  For example, although 1992 was a quieter than average hurricane season with only 7 tropical storms, it featured one of the worst hurricanes in U.S. history.  Hurricane Andrew was only the third Category 5 storm on record to make landfall in the United States when it came ashore in south Florida in August 1992.  Last season was also quiet in the Atlantic Ocean with 8 named tropical storms.  However, 2014 saw the Atlantic’s first Category 4 hurricane (Gonzalo) since 2011.

In a rare occurrence, the first tropical storm of the 2015 season already developed before this season officially began on May 8 when “Ana” was named.  Tropical Storm Ana made landfall in South Carolina.  June and July are typically quiet in the tropics as the ocean water continues to warm to the 80 degree threshold they require to develop.  Mid-August to Mid-October is typically the busiest period of the hurricane season.  Hurricane season ends on November 30.  NOAA will update their seasonal forecast in early August.

My colleagues and I on the WUSA9 Weather Team will keep viewers apprised of the latest weather conditions in the tropics both on-air and online.  The next tropical storm that develops will be named “Bill.”