Note to Editors: The complete hurricane forecast report and a list of frequently asked questions are available at http://newsinfo.colostate.edu/index.asp. Charts and previous forecasts will be available after 8 a.m. MST at http://hurricane.atmos.colostate.edu.
The hurricane forecast team at Colorado State continues to downgrade its 2006 forecast for the Atlantic basin based on changing climate signals and below-average activity in the first third of the season.
The forecasting team of Philip Klotzbach and William Gray today released a new report that calls for a total of 13 named storms to form in the Atlantic basin this season. Of these, five are predicted to become hurricanes and two are anticipated to evolve into intense hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater. The new forecast is down from the team’s August forecast of 15 named storms, seven hurricanes and three intense hurricanes.
The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
"We predict September and October will exhibit characteristics of a more average year based on the activity so far this season and climate signals through August," Klotzbach said. "Current conditions in the Atlantic indicate that we will now see a slightly below-average hurricane season with far less activity than was experienced in each of the last two years."
These changes include dryer tropical Atlantic mid-level moisture fields, high levels of West African dust over the Atlantic, and a warmer eastern equatorial Pacific indicating a potential El Nio event this fall.
June and July experienced average amounts of tropical cyclone activity with two named storms forming – Alberto and Beryl. Unlike 2005 when two major hurricanes – Dennis and Emily – developed and intensified in the tropical Atlantic and Caribbean, no hurricane activity occurred in the deep tropics during June and July 2006.
August 2006 had about average named-storm activity, but the amount of intense activity was well below-average. Only one hurricane – Ernesto – formed during August – and lasted less than one day due to interaction with land. On average, about six hurricane days occur during August.
The Colorado State hurricane team’s monthly predictions through October:
-The September-only forecast calls for five named storms, three hurricanes and two major hurricanes, which is slightly above-average for September.
-The October-only forecast calls for two named storms, one hurricane and no major hurricanes, which is below average.
"Despite the lower predictions, residents living along the U.S. coastline should always be prepared for major storms," Gray said.
The hurricane forecast team has said the United States has been fortunate over the past few decades – until the 2004 and 2005 seasons – in experiencing only a few major hurricanes making U.S. landfall.
Between 1995 and 2003, 122 named storms, 69 hurricanes and 32 major hurricanes formed in the Atlantic basin. During that period, only three of the 32 major hurricanes – Opal, Bret and Fran – crossed the U.S. coastline. Based on historical averages, about one in three major hurricanes that forms in the Atlantic basin comes ashore in the United States.
But in the past two years, 13 major hurricanes formed in the Atlantic basin – seven of them striking the U.S. coast.
"For many years, we have been warning of the return of major hurricane landfall events similar to what was experienced in the 1940s through the 1960s," Klotzbach said. "We also warned that destruction was likely to be higher than was previously experienced due to increased coastal population and wealth per capita."
"We recommend that there not be too much read into the last two hurricane seasons of 2004-2005," Gray said. "The activity of these two years was unusual but well within natural bounds of hurricane variation. This is how nature sometimes works."
What made the 2004-2005 seasons so unusually destructive was not the high frequency of major hurricanes but the high percentage of major hurricanes that were steered over the U.S. coastline. These major landfalling hurricane events were primarily a result of favorable upper-air steering currents present over the past two seasons.
The team continuously works to improve forecast methodologies based on a variety of climate-related global and regional predictors.
For a detailed description of the many detailed forecast factors, visit the Web at http://tropical.atmos.colostate.edu.
The team will issue a seasonal update and an updated monthly forecast for October 2006 Atlantic basin hurricane activity on Oct. 3.