As the Atlantic remains much quieter on the storm front than many expected just a few short months ago, respected hurricane forecasters William Gray and Philip Klotzbach of the Colorado State University (CSU) hurricane forecast team reduced their 2006 Atlantic hurricane season predictions last week for the third time since late May. While the forecasters added one more hurricane to their September prediction, they decreased their overall storm prediction by two.
Gray and Klotzblach said developing El Nino conditions in the central and eastern Pacific have led the team to continue to call for below-average activity for the remainder of the 2006 Atlantic basin hurricane season. The new forecast released Tuesday calls for two more named storms, one more hurricane and no more intense or major (Saffir/Simpson category 3-4-5) hurricanes for the remainder of the hurricane season (October-November).
With the observed activity through September 2006 of nine named storms, five hurricanes and two major hurricanes, a total of 11 named storms are predicted to form in the Atlantic basin during 2006 with six of these predicted to become hurricanes. Two major hurricanes with sustained winds of 111 mph or greater have already formed, and the forecast team said it does not expect any more major hurricane formations this year.
In September, the CSU team predicted 13 named storms, five of which would become hurricanes with two major hurricanes (see NGI, Sept. 11). The September forecast was down from the team’s August forecast of 15 named storms, seven hurricanes and three intense hurricanes (see NGI, Aug. 7). In late May (see NGI, June 5), Klotzbach and Gray had called for 17 named storms, nine hurricanes and five major hurricanes. The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
“We have experienced average hurricane activity through September,” said Klotzbach, lead author of the forecast. “August was inactive, but September had above-average activity. We expect October to have below-average activity largely due to developing El Nino conditions in the central and eastern Pacific. November activity in El Nino years is very rare.”
The team said Atlantic basin tropical cyclone activity for the 2006 season will be considerably less than previously predicted largely because of the unexpected El Nino conditions that developed late this summer as well as the development of mid-level dryness in the tropical Atlantic — with large amounts of African dust — that greatly reduced August activity.
“Typically, El Nino conditions put an early end to hurricane formation in the Atlantic basin,” Gray said. “This year, El Nino has developed faster than almost anyone predicted.”
The team noted that while June and July 2006 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. Three named storms (Chris, Debby and Ernesto) formed during August, but only Ernesto briefly reached hurricane status. Four named storms (Florence, Gordon, Helene and Isaac) formed during September, and all four became hurricanes with Gordon and Helene became major hurricanes. No hurricanes have struck the U.S. coastline so far this season.
The forecasters said the United States has been very fortunate over the past few decades — until the 2004 and 2005 seasons — in experiencing only a few major hurricanes making U.S. landfall. The team explained that 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, the team said.
Gray and Klotzblach said a verification and discussion of all 2006 forecasts will be issued on Nov. 17 followed by the first 2007 seasonal hurricane forecast in early December.
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