The upcoming hurricane season will likely be quieter than average, NOAA said today in their seasonal outlook, indicating that a strengthening El Niño and cool ocean temperatures will probably lead to unfavorable hurricane conditions over the Atlantic Ocean.
However, NOAA cautions that even a below-average season can still be active in terms of landfalls and damage, and that preparedness is crucial no matter the outlook.
On the whole, the NOAA outlook calls for a 70 percent chance of a below-average season, with a 20 percent chance for average storm totals, and a 10 percent chance of above average. Breaking the numbers down, NOAA is predicting the season will feature six to 11 named storms, three to six of which could become hurricanes, and up to two major hurricanes. The average number of named storms is 12, with six reaching hurricane status and three becoming major hurricanes.
“This is the highest probability of a below-average season since about 1998,” said NOAA administrator Kathryn Sullivan.
NOAA cites the current, potentially strengthening El Niño and cooler than average ocean temperatures as rationale for the below-average forecast. El Niño tends to dampen hurricane formation in the Atlantic by increasing wind shear, or the change in wind speed with height. In an environment with high wind shear, weak tropical disturbances have a more difficult time growing tall in the atmosphere. Warm sea surface temperature is the driving force behind hurricane intensity, and cooler temperatures decrease not only the intensity of the storms that do form, but also the formation of storms in general.
However, the below-average forecast doesn’t predict anything about landfalls, and it only takes one hurricane to do widespread damage. Hurricane Andrew in 1992 is the poster child for major hurricane landfalls in an otherwise “quiet” season. Andrew formed during the tail end of an El Niño and was the only hurricane to make landfall that year, devastating the southeast Florida coastline and becoming the costliest storm on record at the time.
— Natl Hurricane Ctr (@NHC_Atlantic) May 27, 2015
The caveat to the “quiet” outlook is exacerbated by the dearth of major hurricane landfalls over nearly the past decade, and even more so the lack of any hurricane landfall of any intensity in Florida since Wilma in 2005. In that time, more than 1 million people have moved to Florida who might have no experience preparing for or responding to a landfalling hurricane.
NOAA’s outlook is in line with those from other organizations, both academic and private, issued to date (see below). Last month, Colorado State University research scientist Phil Klotzblach released what he said is the group’s lowest-ever forecast issued in April. The U.K. Met Office, as well as private companies such as WeatherBELL Analytics and WSI, a sister company of the Weather Channel, are also predicting seasons well below average. Only London-based weather consortium Tropical Storm Risk is forecasting a season close to average, with 11 named storms, five hurricanes and two major hurricanes.
The Atlantic season, which by definition begins on June 1, got off to a somewhat early start with Subtropical Storm Ana in early May. Although “preseason” storms that spin up before June 1 occur on average every four to five years, Ana was the earliest first-named storm since April 20, 2003, when another Subtropical Storm Ana formed.