Colorado State University Hurricane Team Calls for Above-Average 2011 Hurricane Season in Early December Forecast

Note to Reporters: The entire forecast report will be available on the web at or with the news release at no later than 8 a.m. MST.

The Tropical Meteorology Project at Colorado State University today called for an above-average Atlantic basin hurricane season in an early extended-range forecast for 2011.

The report marks the 28th year for the CSU hurricane forecasting team which is led by Philip Klotzbach and William Gray.

The team anticipates 17 named storms, 9 hurricanes and 5 major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater for the 2011 hurricane season, which runs from June 1 through Nov. 30. These forecast numbers for 2011 are close to the active Atlantic basin hurricane season experienced in 2010.

For 2010, the team accurately predicted well above-average hurricane activity for the Atlantic basin. Just as hurricane season began in June, the team called for 18 named storms, 10 hurricanes and five major (Category 3-4-5) hurricanes. Observed were 19 named storms, 12 hurricanes and five major hurricanes.

“The U.S. was extremely lucky in 2010 in that none of the 12 Atlantic basin hurricanes that formed crossed the U.S. coastline,” Klotzbach said. “On average, about 1 in 4 Atlantic basin hurricanes makes U.S. landfall, and therefore, we would expect to see more landfalling hurricanes in 2011.

"There is significant uncertainty with this earliest outlook, issued six months prior to the start of the hurricane season. Given the current upper ocean heat content anomalies in the tropical Pacific, we believe that El Nino conditions are unlikely. This could mean a more active hurricane season,” Klotzbach said.

“This forecast is based on an extended-range early December statistical prediction scheme we’ve developed based on 58 years of data,” Gray said. “At this point, we are uncertain whether La Nina conditions or neutral conditions are more likely for the 2011 hurricane season. Sea surface temperatures in the far North Atlantic remain at record warm levels, which is an indication that we are in an active multi-decadal period for Atlantic hurricane activity.”

The statistical model used by the CSU Hurricane Forecast Team explains a considerable amount of hurricane variability in hindcasts issued from 1950-2007. Over this time period, the three-predictor scheme correctly forecast above- or below-average seasons in 44 out of 58 years.

For the 2011 Atlantic basin hurricane season, the CSU hurricane forecast team predicts:

• A 73 percent chance that at least one major hurricane will make landfall on the U.S. coastline in 2011. The long-term average probability is 52 percent.

• For the U.S. East Coast, including the Florida Peninsula, the probability of a major hurricane making landfall is 49 percent (the long-term average is 31 percent).

• For the Gulf Coast from the Florida Panhandle west to Brownsville, the probability is 48 percent (the long-term average is 30 percent).

• The team predicts the probability of a major hurricane making landfall in the Caribbean as 62 percent (average for the last century is 42 percent).

Along with today’s report, the team has updated the Landfall Probability Web site that provides probabilities of tropical storm-force, hurricane-force and major hurricane-force winds making landfall at specific locations along the U.S. East and Gulf Coasts within a variety of time periods. U.S. landfall probabilities are available for 11 regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine. Probabilities are also available for Central America and the Caribbean. With the help of Bridgewater State College in Massachusetts, the website is available to the public at

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

The team will issue seasonal updates of its 2011 Atlantic basin hurricane activity forecast on April 6, June 1 and Aug. 3.

Tropical Cyclone Parameters Extended Range
(1950-2000 Averages in parentheses) Forecast for 2011
Named Storms (9.6) 17
Named Storm Days (49.1) 85
Hurricanes (5.9) 9
Hurricane Days (24.5) 40
Major Hurricanes (2.3) 5
Major Hurricane Days (5.0) 10
Accumulated Cyclone Energy (96.7) 165
Net Tropical Cyclone
Activity (100%) 180