The 2009 Atlantic hurricane season officially gets underway on June 1, and forecasters are predicting that it will be anything but severe.
According to the extended range forecast of Philip J. Klotzbach and William M. Gray of Colorado State University, the 2009 hurricane season has only an average probability of a major hurricane making landfall in the United States.
Released on April 7, the forecast predicts a relatively calmer season than that of last year with 12 named storms and 6 hurricanes, 2 of which are expected to be between category 3-5.
In contrast, the 2008 hurricane season saw 16 named storms and 8 hurricanes, 5 of which were category 3 or higher.
CSU’s extended range hurricane forecast is based on statistical analysis of cyclone activity in the Atlantic basin over the last 58 years. It also looks at current surface temperatures and takes into account the likely trends of both the La Nina and El Nino phenomena, all of which can affect the development of hurricanes.
If La Nina conditions subside and El Nino conditions begin to develop, the resulting rise in temperature would increase vertical wind shear and thus lower the degree of hurricane activity.
Currently however, cool surface temperatures which are being deemed anomalous by researchers are being observed and are expected to play a larger role in this year’s relatively weak hurricane season.
The life of a hurricane begins just North or South of the equator over ocean water that is at least 80 degrees Fahrenheit. It starts off as a much smaller and less violent tropical storm but grows in size and intensity as it feeds off the warm water and quickly rises thousands of feet into the air. The result of this ascent is that as the storm rises into the cooler air above, it creates an atmospheric disturbance in the general area that allows for sustained activity. This gives the system time to gather more heat from the ocean and to essentially funnel it upwards as it grows larger. Eventually, it grows large enough to reach heights that facilitate extremely rapid cooling, which creates an even larger atmospheric disturbance. This will allow all the surrounding air to become susceptible to the Coriolis Force, and from sea level to as high as 30,000 feet it will begin to move in the same direction, thus creating the familiar cyclone. It will then begin to move off and will either grow or dissipate depending on temperature, humidity and level of wind shear.
Philip J. Klotzbach and William M. Gray, 2009 Atlantic Seasonal Hurricane Forecast, The Tropical Meteorology Project
Tropical Cyclone Formation, Environment Canada
2008 Atlantic hurricane season, Wikipedia