Colorado State University Hurricane Forecast Team Continues to Call for Above-Average Atlantic Basin Activity

Note to Reporters: Downloadable photos and a full copy of the 2011 hurricane season report may be found with the news release at or at

The Colorado State University hurricane forecast team today maintained its earlier season hurricane forecast, calling for 16 named storms in the Atlantic basin for the 2011 season.

Above-normal sea-surface temperatures and expected reduced vertical shear in the tropical Atlantic along with near-neutral El Nino-Southern Oscillation (ENSO) conditions will likely contribute to an above-average season. The team held to its April prediction of 16 named storms with nine of the 16 becoming hurricanes in the Atlantic basin between June 1 and Nov. 30. Five are expected to develop into major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.

“We are predicting the same levels of activity that were forecast in early April due to favorable atmospheric and oceanic conditions in the tropical Atlantic,” said William Gray, in his 28th year of forecasting at Colorado State. “We continue to anticipate an above-average probability of United States and Caribbean major hurricane landfall.”

Klotzbach and Gray estimate the 2011 season will have roughly as much activity as was experienced in five similar years: 1951, 1981, 1989, 1996, and 2008.

The team also updated its U.S. landfall probabilities, which are calculated based on historical landfall statistics and then adjusted by the latest seasonal forecast.

“Based on our historical analysis along with our current forecast, the probability of a major hurricane making landfall along the U.S. coastline is approximately 72 percent,” said lead forecaster Phil Klotzbach. “These probabilities are based on the idea that more active seasons tend to have more landfalls, but coastal residents should prepare the same way every year for landfall, regardless of how active or inactive the forecast might be.”

Other probabilities for a major hurricane making landfall on various portions of the U.S. coast:

– A 48 percent chance that a major hurricane will make landfall on the U.S. East Coast, including the Florida Peninsula (the long-term average is 31 percent).

– A 47 percent chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville (the long-term average is 30 percent).

-A 61 percent change of a major hurricane tracking into the Caribbean (average for the last century is 42 percent).

Probabilities of tropical storm-force, hurricane-force and major hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts within a variety of time periods are listed on the forecast team’s Landfall Probability Web site. The site provides U.S. landfall probabilities for 11 regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine. Individual state probabilities are also available. Gray and Klotzbach recommend that coastal residents consult this website to learn of their local hurricane impact probabilities on multiple timescales.

The website, available to the public at, is the first publicly accessible internet tool that adjusts landfall probabilities for regions, states and counties 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 College in Massachusetts. In addition, probabilities for various islands in the Caribbean and landmasses in Central America are now available on the Landfall Probability Web site.

The hurricane forecast team predicts tropical cyclone activity in 2011 will be approximately 175 percent of the average season. By comparison, 2010 witnessed tropical cyclone activity that was about 196 percent of the average season.

The hurricane team’s forecasts are based on the premise that global oceanic and atmospheric conditions – such as El Nino, sea surface temperatures and sea level pressures – that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.

The team will issue a final seasonal forecast update on Wednesday, August 3.

-Released June 1, 2011-
Tropical Cyclone Parameters Extended Range
(1950-2000 Climatology Averages Forecast for 2011
in parentheses)
Named Storms (9.6)* 16
Named Storm Days (49.1) 80
Hurricanes (5.9) 9
Hurricane Days (24.5) 35
Intense Hurricanes (2.3) 5
Intense Hurricane Days (5.0) 10
Accumulated Cyclone Energy (96) 160
Net Tropical Cyclone
Activity (100%) 175
* Numbers in ( ) represent average year totals based on 1950-2000 data.