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Research / Discovery

Hurricane Forecast Team reduces forecast, predicts average season in 2009

April 7, 2009

The Colorado State University forecast team predicts an average 2009 Atlantic basin hurricane season based on the potential for a weak El Nino event and an observed cooling of tropical Atlantic sea surface temperatures.

12 named storms, 2 major hurricanes

The team lowered its forecast from December and now anticipates 12 named storms forming in the Atlantic basin between June 1 and Nov. 30. Six of the storms are predicted to become hurricanes, and of those six, two are expected to develop into intense or major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.

This forecast has been reduced from the early December prediction of 14 named storms, seven hurricanes and three major hurricanes. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.

Weak La Nina conditions

"We expect current weak La Nina conditions to transition to neutral and perhaps weak El Nino conditions by this year's hurricane season. If El Nino conditions develop for this year's hurricane season, it would tend to increase levels of vertical wind shear and decrease levels of Atlantic hurricane activity," said William Gray, who is beginning his 26th year forecasting hurricanes at Colorado State University.

The team has seen anomalous cooling of sea surface temperatures in the tropical Atlantic over the past few months. Cooler waters are associated with dynamic and thermodynamic factors that are less conducive for an active Atlantic hurricane season.

54% probability of major hurricane making landfall along U.S. coastline

"Based on our latest forecast, the probability of a major hurricane making landfall along the U.S. coastline is 54 percent compared with the last-century average of 52 percent," said lead forecaster Phil Klotzbach of the Colorado State hurricane team. "We are calling for an average hurricane season this year - about as active as the average of the 1950-2000 seasons."

These factors are similar to conditions that occurred during 1951, 1968, 1976, 1985 and 2001 seasons. The average of these five seasons had about average activity, and Klotzbach and Gray predict the 2009 season will have activity in line with the average of these five years.

The team will issue forecast updates on June 2, Aug. 4, Sept. 2 and Oct. 1. The August, September and October forecasts will include separate forecasts of August-only, September-only and October-only Atlantic basin tropical cyclone activity.

Full news release and additional info

Contact: Emily Wilmsen
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