May 26th, 2011

Summary of 2011 Hurricane Season Forecasts

Posted at 1:00 AM ET

With the start of the Atlantic hurricane season just a few days away, Guy Carpenter has summarized the various forecasters’ predictions for the 2011 season. AccuWeather, the Colorado State University (CSU), the National Oceanic and Atmospheric Administration (NOAA) and Weather Services International (WSI) have released forecasts for the forthcoming season and there seems to be a general consensus that 2011 will see above-average activity with an increased risk of hurricane landfalls in the United States. The most recent forecasts are outlined in the table below.

Summary of Hurricane Forecasts for 2011 (Sources: AccuWeather, CSU, NOAA, WSI)

Total Named Storms (>39 mph)

Hurricanes (>74 mph)

Major Hurricanes (>111 mph)

Average storm development (based on data from 1950 – 2009)




AccuWeather (released March 30)




CSU (released April 6)




NOAA (released May 19)




WSI (released April 27)




Although an above-average 2011 season is forecast, hurricane activity is expected to be down compared to last year. The 2010 season was the third most active on record, with the formation of 19 named storms, 12 hurricanes and five major hurricanes. Despite this activity, there was little impact on the United States coastline. For the 2011 season, meteorologists said the main factors affecting the forecasts are the positioning of the Azores/Bermuda high (which influences the path of hurricanes), sea surface temperatures (SSTs) in the Atlantic and the El Niño/La Niña-Southern Oscillation (ENSO).

El Niño, a phenomenon marked by the warming of SSTs in the equatorial Pacific, tends to suppress the development of hurricanes (as demonstrated in 2009). Conversely, La Niña cools SSTs in the Pacific and typically enhances Atlantic basin activity (as seen in 2010). When announcing its 2011 forecast, NOAA said the current La Niña weather system is likely to dissipate in May or June but its lingering impact could reduce wind shear through the 2011 season and drive above-average activity. NOAA also stated SSTs across the Atlantic are up to two degrees Fahrenheit warmer than average.

Although NOAA did not make any landfall predictions for the coming season, other forecasters warn that the United States coastline faces a significant threat. The CSU said that the chances of at least one major hurricane making landfall in the United States in 2011 is 72 percent, notably higher than the long-term average of 52 percent. For the U.S. East Coast, including the Florida Peninsula, the probability of a major hurricane making landfall is 48 percent, again up on the average of 31 percent. For the Gulf Coast, from the Florida Panhandle west to Brownsville, the probability is 47 percent, compared with a long-term average of 30 percent.

AccuWeather has also stated there is likely to be an increased risk of landfalling hurricanes along the U.S. mainland in 2011. Specifically, AccuWeather sees an early season landfall threat in the western Gulf of Mexico and the southern Caribbean, with the Texas and Louisiana coastline particularly vulnerable. The threat shifts into the U.S. Southeast during the middle and late parts of the season, with a high probability of landfall along the Florida Peninsula and the Carolinas, AccuWeather said. AccuWeather also predicted that northern New England and the Canadian Maritime provinces were likely to be threatened towards the end of the season.

WSI added to the consensus when it warned that changing weather conditions could result in multiple landfalling hurricanes along the U.S. coastline this year. WSI said its hurricane landfall prediction model suggests two or three landfalling hurricanes this season, with western Gulf states particularly vulnerable.

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Guy Carpenter’s CAT-i service provides clients with real-time bulletins on natural catastrophes (hurricanes, windstorms, earthquakes, major floods) that have the potential to incur significant losses to the (re)insurance industry. The service provides concise reports summarizing damage details and includes information on the type of event, location, event parameters and the likely magnitude of the economic/insured loss. The reports are updated as soon as new information becomes available. CAT-i subscribers receive the reports in real-time as they are published. CAT-i updates are also freely available on GC, Guy Carpenter’s (re)insurance industry blog, along with additional Guy Carpenter industry-leading intellectual capital.

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