Hurricane Forecast Team at Colorado State University Continues to Call for Active Season

Note to Reporters: Downloadable photos and a full copy of the 2011 hurricane season report may be found with the news release at http://www.news.colostate.edu or at http://hurricane.atmos.colostate.edu/.

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

The combination of neutral El Nino – Southern Oscillation (ENSO) conditions in the tropical Pacific along with continued warm sea surface temperature anomalies and unusually low sea-level pressure anomalies in the tropical Atlantic will likely lead to a very active hurricane season, Colorado State scientists said.

“We are predicting the same levels of activity that we were forecasting in early April and June due to favorable Atlantic and neutral ENSO conditions in the tropical Pacific,” said William Gray, in his 28th year of forecasting at Colorado State.

Klotzbach and Gray estimate the 2011 season will have roughly as much activity as was experienced in four similar years: 1952, 1966, 2005 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.

“After significant warming in the tropical eastern and central Pacific during the late winter and early spring, it appears that neutral conditions are likely to persist for the next several months,” Klotzbach said. “The upper-ocean heat content in the central and eastern tropical Pacific is typically a good indicator of future trends in ENSO. Following dramatic warming during the January-March time period, the upper ocean heat content has leveled off and begun to decrease, which indicates to us that the potential for a transition to El Nino has been greatly reduced.”

For the remainder of the season, Klotzbach also recalculated probabilities for a major hurricane making landfall on the U.S. coast:

• A 70 percent chance that a major hurricane will make landfall on the U.S. coastline (full-season average for the last century is 52 percent)

• A 46 percent chance for the East Coast, including the Florida Peninsula (full-season average for the last century is 31 percent).

• A 45 percent chance for the Gulf Coast from the Florida Panhandle west to Brownsville (full-season average for the last century is 30 percent).

The probability for at least one major hurricane making landfall in the Caribbean is 59 percent (full-season 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 http://www.e-transit.org/hurricane, 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 University 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.

CSU RESEARCH TEAM
EXTENDED RANGE ATLANTIC BASIN HURRICANE FORECAST FOR 2011
-Released Aug. 3, 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
Major Hurricanes (2.3) 5
Major 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.

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