Updating its April forecast (see Daily GPI, April 10), the Colorado State University forecast team led by Phil Klotzbach and William Gray said the U.S. Atlantic basin likely will experience another active hurricane season, but coastal regions may face fewer major hurricanes making landfall than last year.

Maintaining its earlier predictions for the 2006 hurricane season, which starts Thursday, Colorado State’s forecast for the 2006 hurricane season sees 17 named storms, nine hurricanes and five intense hurricanes (Saffir/Simpson Category 3-4-5) with sustained winds of 111 mph or greater. The forecasters noted that long-term averages for activity are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year. The season traditionally ends Nov. 30.

In comparison, the devastating 2005 season witnessed 27 named storms, 15 hurricanes and seven intense hurricanes. As of the Minerals Management Service’s latest report May 3, a total of 1.295 Bcf/d was still offline in the Gulf of Mexico from Hurricanes Katrina, Rita and Wilma in 2005. Since Aug. 26, 2005, a total of 748.9 Bcf production has been lost due to the storms. The 2005 season was unusually destructive because of favorable broad-scale Atlantic upper-air steering currents that caused so many hurricanes to come ashore, Gray said.

The Colorado State team’s assessment of an active season is in line with that of the National Oceanic and Atmospheric Administration (NOAA), which released its updated forecast last week (see Daily GPI, May 23). NOAA is predicting 13 to 16 named storms, with eight to 10 becoming hurricanes, of which four to six could become major hurricanes of Category 3 strength or higher.

“The Atlantic Ocean remains anomalously warm and neutral ENSO (El Nino-Southern Oscillation) conditions are observed in the tropical Pacific,” said Klotzbach. “We expect neutral ENSO conditions to be present during the upcoming hurricane season. When the tropical Atlantic is warm and neutral ENSO conditions are present, Atlantic basin hurricane activity is usually enhanced.”

The hurricane forecast team predicts that tropical cyclone activity in 2006 will be 195% of the average season. By comparison, 2005 witnessed tropical cyclone activity that was about 275% of the average season.

“If the atmosphere and the ocean behave as they have in the past, we should have a very active season, but that doesn’t necessarily translate into storms that produce as much destruction as last year,” said Gray, who has led the Colorado State hurricane forecast team for 22 years.

As previously stated, the current active period of Atlantic major hurricane activity is expected to continue for another 15 to 20 years. However, Gray said it is statistically unlikely that the coming 2006-2007 hurricane seasons, or those that follow, will have the number of major hurricane U.S. landfall events as occurred in 2004-2005.

The hurricane forecast team’s probabilities for a major hurricane making landfall on U.S. soil are as follows:

The team also predicted above-average major hurricane landfall risk in the Caribbean. The forecast team’s landfall probabilities for the United States are based upon total predicted Net Tropical Cyclone activity, which is an aggregate measure of activity expected during the season and new mid-level steering flow predictors that show moderate skill in predicting whether storms are more likely to make landfall along the Gulf Coast, the Florida Peninsula and East Coast, or stay out to sea without making landfall. The team found that this year’s steering current predictors indicate that the Florida peninsula and East Coast have an especially heightened risk of experiencing hurricanes.

“In any one season, most U.S. coastal areas will not feel the effects of a hurricane no matter how active a season,” Klotzbach said. “The probability of landfall for any one location along the coast is very low. However, low landfall probability does not ensure that hurricanes will not come ashore, so coastal residents should always be prepared.”

According to the Landfall Probability Project, which Klotzbach and Gray update regularly, the Texas Gulf coast has a 28.4% chance of being within the vicinity of an intense hurricane this season, while the eastern sliver of the Texas Gulf Coast and the western half of the Louisiana Gulf Coast stand an 11.6% chance of being within the vicinity of an intense hurricane. The eastern half of the Louisiana coast through the western edge of the Florida Gulf Coast stands a 25.8% chance of being within the vicinity of an intense hurricane, while the rest of Florida’s Gulf Coast acreage has a 5.1-15.3% chance of being within the vicinity of an intense hurricane. For a detailed desription of tropical storm-force, hurricane-force and intense hurricane-force winds that are expected to occur at specific locations along the U.S. East and Gulf Coasts, visit www.e-transit.org/hurricane.

The hurricane team said its forecasts are based on the premise that global oceanic and atmospheric conditions — such as El Niño, sea surface temperatures and sea level pressure — that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons. For 2006, Gray and the hurricane forecast team expect continued warm tropical and north Atlantic sea surface temperatures, prevalent in most years since 1995, as well as neutral ENSO conditions, which is “a recipe for enhanced Atlantic basin hurricane activity.” The team found these factors are similar to conditions that occurred during the 1961, 1996, 2001 and 2004 seasons. The average of these four seasons had well above average activity, and Klotzbach and Gray predict that the 2006 season will have comparable activity to the average of these four years.

In studying the possibility that changes in Atlantic hurricane activity is tied somehow to global warming, Gray said he continues to see no such linkage. “Nature is causing these things — it’s not human-induced global warming,” he said. “Seasonal and monthly variations of sea surface temperature within individual storm basins show low correlations with monthly, seasonal and yearly variations of hurricane activity.”

The entire Atlantic hurricane forecast is available at https://hurricane.atmos.colostate.edu. The team said it will issue seasonal updates of its 2006 Atlantic basin hurricane activity forecast on Aug. 3, Sept. 1 and Oct. 3.

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