Uncertain weather factors yield 50-50 prediction

• By AMY WOLD
• Advocate staff writer
• Published: May 31, 2009

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There’s a 50 percent chance the 2009 hurricane season will be an average one, according to forecasters with National Oceanic and Atmospheric Administration.

NOAA officials also predicted on May 21 that there is a 70 percent chance the 2009 season will have between nine to 14 named storms.

Of those, four to seven could grow into hurricane strength with one to three of those being major hurricanes with wind speeds of Category 3, 4 or 5. Storms in those categories have sustained winds of more than 110 mph.

A long-term average for a hurricane season is 11 named storms. Six of those storms become hurricanes, and two become major hurricanes, according to NOAA.

The 2009 hurricane season officially starts June 1 and runs through November.

However, there are more uncertainties with this year’s forecast than in recent years, said Gerry Bell, NOAA’s lead seasonal Atlantic hurricane forecaster.

Because of a number of uncertain weather patterns and conditions, there is about a 50 percent chance of having an average season. There is also a 25 percent chance of an above-average season, meaning more storms, and a 25 percent chance of a below average season.

One of these uncertainties is the Atlantic Multidecadal Oscillation — an up-and-down temperature cycle in the Atlantic Ocean that triggers decades of more active or less active hurricane seasons. Currently, the Atlantic Ocean is in the warmer and more active period, Bell said.

“We’re now 14 years into this high-activity area, and there’s no indication it’s coming to a close,” Bell said.

However, this warmer cycle could be countered if an El Niño forms in the Pacific Ocean this summer. This weather pattern increases the upper atmosphere winds and helps to “cap” a hurricane’s formation, while the opposite occurs during a La Niña.

In addition, storm strengthening could be hindered if the ocean temperatures in the eastern tropical Atlantic Ocean continue to be cooler than normal, Bell said.

As these conditions form, or fail to form, Bell said he’d be able to have a more refined forecast in August.

Regardless of the hurricane forecast, NOAA, state and local officials urge people to take personal responsibility and get prepared for the season.