Atmospheric and oceanic conditions are primed to fuel an “extremely active” storm season in the Atlantic, with the potential to be one of the busiest on record, forecasters with the National Oceanic Atmospheric Administration (NOAA) said Thursday.

NOAA’s Climate Prediction Center (CPC), a division of the National Weather Service, every August provides an Atlantic hurricane update from the initial forecast in May. The updated outlook for the season, which ends Nov. 30, calls for 19-25 named storms (including the nine to date), with winds of at least 39 mph. May’s forecast had predicted 13-19 named storms.

Seven to 11 storms are forecast to become hurricanes, with winds of at least 74 mph, with three to six that could form into major storms, i.e. Category (Cat) 3, 4 or 5, with winds of at least 111 mph. 

“This is one of the most active seasonal forecasts that NOAA has produced in its 22-year history of hurricane outlooks,” said Commerce Secretary Wilbur Ross. 

Historically, only two named storms form on average by early August, with the ninth named storm typically not forming before Oct. 4, NOAA noted. 

However, Hurricane Isaias, which plundered the Carolinas in the first weekend of August then meandered up the Eastern Seaboard this week, was the ninth storm. Hurricane Hanna came ashore in South Texas in late July.  

An average season produces 12 named storms, including six hurricanes, three of which become Cat 3-5 hurricanes.

Overall hurricane season activity is measured by the Accumulated Cyclone Energy (ACE) index, which measures the combined intensity/duration of all named storms during the season. Based on the ACE projection, combined with the above-average numbers of named storms and hurricanes, “the likelihood of an above-normal Atlantic hurricane season has increased to 85%, with only a 10% chance of a near-normal season and a 5% chance of a below-normal season,” forecasters said.

“This year, we expect more, stronger, and longer-lived storms than average, and our predicted ACE range extends well above NOAA’s threshold for an extremely active season,” said lead CPC seasonal forecaster Gerry Bell.

Current oceanic and atmospheric conditions that could create an “extremely active” hurricane season are warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and Caribbean Sea, reduced vertical wind shear, weaker tropical Atlantic trade winds and an enhanced West Africa monsoon, NOAA said. Those conditions are expected to continue “for the next several months.”

There also is the possibility of a La Nina developing in the months ahead. La Nina, created cooler-than-average sea surface temperatures in the equatorial regions of the eastern Pacific Ocean, could further weaken the wind shear over the Atlantic Basin, allowing storms to develop and intensify.