May 21, 2009
NOAA forecasters say a near-normal Atlantic hurricane season is most likely this year. However, as with any season, the need to prepare for the possibility of a storm striking near you is essential.
In its initial outlook for the 2009 Atlantic hurricane season, which runs from June through November, NOAA’s National Weather Service Climate Prediction Center calls for a 50 percent probability of a near-normal season, a 25 percent probability of an above-normal season and a 25 percent probability of a below-normal season. Global weather patterns are imposing a greater uncertainty in the 2009 hurricane season outlook than in recent years. Forecasters say there is a 70 percent chance of having nine to 14 named storms, of which four to seven could become hurricanes, including one to three major hurricanes (Category 3, 4 or 5).
“This outlook is a guide to the overall expected seasonal activity. However, the outlook is not just about the numbers, it’s also about taking action,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center. “Prepare for each and every season regardless of the seasonal outlook. Even a near- or below-normal season can produce landfalling hurricanes, and it only takes one landfalling storm to make it a bad season.”
Shaping this seasonal outlook is the possibility of competing climate factors. Supporting more activity this season are conditions associated with the ongoing high-activity era that began in 1995, which include enhanced rainfall over West Africa, warmer Atlantic waters and reduced wind shear. But activity could be reduced if El Nino develops in the equatorial Eastern Pacific this summer or if ocean temperatures in the eastern tropical Atlantic remain cooler than normal.
NOAA’s seasonal hurricane outlook does not project where and when any of these storms may hit. Landfall is dictated by weather patterns in place at the time the storm approaches. For each storm, NOAA’s National Hurricane Center forecasts how these weather patterns affect the storm track, intensity and landfall potential.
Tropical systems acquire a name – the first for 2009 will be Ana – upon reaching tropical storm strength with sustained winds of at least 39 mph. Tropical storms become hurricanes when winds reach 74 mph, and become major hurricanes when winds increase to 111 mph. An average season has 11 named storms, including six hurricanes with two becoming major hurricanes.
NOAA scientists will continue to monitor evolving conditions in the tropics and will issue an updated hurricane outlook in early August, just prior to what is historically the peak period for hurricane activity.
NOAA understands and predicts changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.