The first day of the 2011 Atlantic hurricane season started right on cue Wednesday with a small area of low pressure forming off the east coast of Florida, and forecasters at Colorado State University (CSU) said they expect that system signals the opening of six months of above-average tropical storm activity.
The CSU forecast team, known as the CSU Tropical Meteorology Project, is forecasting 16 named storms forming in the Atlantic Basin by Nov. 30, with nine turning into hurricanes, five of them major hurricanes (Category 3 or higher). A combination of expected neutral El Nino Southern Oscillation conditions and favorable atmospheric and oceanic conditions in the tropical Atlantic will be the major factors determining hurricane production, they said.
"We continue to foresee well above-average activity in the 2011 Atlantic hurricane season," the CSU forecasters said.
The first low-pressure area of the season, which was located about 200 miles east of Jacksonville, FL, Wednesday morning, moved west-southwest toward Florida's west coast during the day, spreading shower and thunderstorm activity over portions of northern and central Florida by mid-afternoon. Significant development of the system was not anticipated as it moved over land through Wednesday night, according to the National Hurricane Center (NHC). There was a 20% chance of the system becoming a tropical cyclone by Friday afternoon, NHC said. By that time the system could have moved over the northwestern Gulf of Mexico. If the system strengthens into a storm, it will be named Arlene, NHC said.
NHC was also tracking disorganized cloudiness and showers associated with a broad surface trough over the southwestern and west-central Caribbean Sea. Some gradual development of that system was possible once upper-level winds become more conducive late Thursday and Friday, but there was only a 10% chance of the system becoming a tropical cyclone, NHC said.
The CSU forecast team said it sees a 72% chance that at least one major hurricane will make landfall on the U.S. coastline this year. Probabilities first issued by CSU in April include a 48% chance that a major hurricane will make landfall on the U.S. East Coast, including the Florida peninsula (the long-term average is 31%); a 47% chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville, TX (the long-term average is 30%); and a 61% chance of a major hurricane tracking into the Caribbean (the long-term average is 42%) (see Daily GPI, April 7).
A total of 19 named storms formed in 2010, with 12 of them becoming hurricanes, including five intense hurricanes. The long-term (1950-2009) averages for the Atlantic hurricane season are 10 named storms, six hurricanes and two intense hurricanes; the 1995-2009 averages are 14, eight and four, respectively.
The consensus forecast is for an active hurricane season this year, with WSI Corp. (see Daily GPI, May 25), the National Oceanic and Atmospheric Administration (see Daily GPI, May 20), AccuWeather.com (see Daily GPI, April 26; April 1) and MDA EarthSat all calling for above-average numbers of named storms and hurricanes.
The 2011 Atlantic hurricane season isn't likely to produce as many hurricanes as 2010, but is likely to send at least one tropical storm into the North American coastline, according to most forecasts.
The CSU team said it will issue a forecast update on Aug. 3.
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