CSU team predicts well below-average hurricane season

Colorado State University researchers continue to predict a well below-average hurricane season for the Atlantic basin in 2015, citing the likely development of a strong El Niño event as well as continued unfavorable hurricane formation conditions in the tropical Atlantic.

The CSU Tropical Meteorology Project team is calling for eight named storms during the Atlantic hurricane season, which officially runs from June 1 to Nov. 30. The eight named storms that are predicted include Ana, which developed in early May. Of those eight named storms, researchers expect three to become hurricanes and one to reach major hurricane strength (Saffir/Simpson category 3-4-5) with sustained winds of 111 miles per hour or greater.

The team bases its forecasts on over 60 years of historical data that include Atlantic sea surface temperatures, sea level pressures, vertical wind shear (the change in wind direction and speed with height in the atmosphere), El Niño (warming of waters in the central and eastern tropical Pacific), and other factors.

Similar to past seasons

So far, the 2015 season is exhibiting characteristics similar to the 1957, 1965, 1972, 1982, 1987 and 1997 hurricane seasons, all of which had below-normal activity, said Phil Klotzbach, lead author of the report.

“The tropical Atlantic continues to exhibit conditions that are less conducive for tropical cyclone formation, and the chances of a strong El Niño event this summer and fall appear to be quite high,” Klotzbach said. “Historical data indicate fewer storms form in these conditions.”

The team predicts that 2015 tropical cyclone activity will be about 45 percent of the average season. By comparison, 2014’s tropical cyclone activity was about 75 percent of the average season.

The CSU team will issue another forecast update Aug. 3.

This is the 32nd year that CSU researchers have issued the Atlantic basin season hurricane forecast. William Gray launched the report in 1984.

The CSU forecast is intended to provide a best estimate of activity to be experienced during the upcoming season, not an exact measure.

Klotzbach cautioned coastal residents to take the proper precautions, regardless of the below-average basinwide forecast. Inactive Atlantic hurricane seasons can still have major U.S. hurricane damage, with two relatively recent notable examples being 1983 (Hurricane Alicia) and 1992 (Hurricane Andrew).

“It takes only one landfall event near you to make this an active season,” he said.

Landfall probability

The report also includes the probability of major hurricanes making landfall on U.S. soil:

  • 28 percent for the entire U.S. coastline (average for the last century is 52 percent)
  • 15 percent for the U.S. East Coast including the Florida peninsula (average for the last century is 31 percent)
  • 15 percent for the Gulf Coast from the Florida panhandle westward to Brownsville (average for the last century is 30 percent)
  • 22 percent for the Caribbean (average for the last century is 42 percent)

The full report and photos are available at tropical.atmos.colostate.edu/.

The forecast team also tracks the likelihood of tropical storm-force, hurricane-force and major hurricane-force winds occurring at specific locations along the coastal United States, the Caribbean and Central America through its Landfall Probability website (www.e-transit.org/hurricane). The site provides information for all coastal states as well as 11 regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine.

Landfall probabilities for regions and counties are adjusted based on the current climate and its projected effects on the upcoming hurricane season.

Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State University in Massachusetts.

Funding for this year’s report has been provided by Interstate Restoration, Ironshore Insurance, Macquarie Group and a grant from the G. Unger Vetlesen Foundation.

-Released June 1, 2015-

Tropical Cyclone Parameters Extended Range
(1981-2010 Climatological Median Forecast for 2015 in parentheses)
Named Storms (12) 8
Named Storm Days (60.1) 30
Hurricanes (6.5) 3
Hurricane Days (21.3) 10
Major Hurricanes (2.0) 1
Major Hurricane Days (3.9) 0.5
Accumulated Cyclone Energy (92) 40