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April 2005                                                                            Volume 8 - Number 3

Preparedness Updates...

Gray’s and Klotzbach’s Predictions for the 2005 Hurricane Season

By Anhdai Tran

On 3 December 2004, Dr. William Gray, Philip Klotzbach, and their hurricane team at Colorado State University released their predictions for the 2005 hurricane season. The predictions, which Dr. Gray has issued and updated since 1983, are detailed in the report, “Extended Range Forecast of Atlantic Seasonal Hurricane Activity and U.S. Landfall Strike Probability for 2005.”

Hurricane season officially begins on 1 June and lasts until 30 November. For 2005, Gray and Klotzbach forecast a “slightly above-average hurricane season,” although not as active as the 2004 season. In addition, they predict:

-- 11 named storms (tropical storms and hurricanes)

-- 6 hurricanes (3 of which will be intense: Category 3 to 5, winds 111 miles per hour and higher)

-- 49% probability that a major hurricane (Category 3 to 5) will hit Florida and the East Coast

-- 39% probability that a major hurricane (Category 3 to 5) will hit the Gulf Coast

-- No major El Nino event

This can be compared with actual tropical storm and hurricane activities in previous years:

-- 2000: 14 named storms; 8 hurricanes (3 of which were major hurricanes)

-- 2001: 15 named storms; 9 hurricanes (4of which were major hurricanes)

-- 2002*: 12 named storms; 4 hurricanes (2of which were major hurricanes)

-- 2003: 16 named storms; 7 hurricanes (3of which were major hurricanes)

-- 2004: 14 named storms; 9 hurricanes (9of which were major hurricanes)

(* = El Nino Year)

Since 1995, forecast procedures—based on the relationships between the West African rainfall and the stratospheric Quasi-Biennial Oscillation with the major hurricane activities in the Atlantic basin in the following 6-11 months—have proved inaccurate. As such, the 2005 predictions are based on a statistical forecast procedure that Gray and Klotzbach recently developed. The new extended forecast procedure uses six predictors located in various parts of the world: far North Atlantic, Gulf of Alaska, Western North America, Equatorial U, Southeast United States, and Subtropical Northeast Pacific. These six predictors were shown to be accurate in hindsight analysis of hurricane activity in previous years.

Gray and Klotzbach will issue seasonal updates of their predictions on 1 April, 31 May, 5 August, 2 September and 3 October 2005.

Gray’s and Klotzbach’s forecasts are available at: http://hurricane.atmos.colostate.edu/Forecasts