Above-average year expected

• By AMY WOLD
• Advocate staff writer
• Published: Jun 1, 2008 - UPDATED: 12:05 a.m.

• Print
• Email
• Save
• Reprints
• Twitter
• Share

• Del.icio.us
• Digg
• Facebook
• Reddit
• 

Hurricane season starts June 1, and forecasts are pointing toward another at or above-average year, according to a release May 22 from the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

The center is predicting 12 to 16 named tropical storms and hurricanes, with six to nine becoming hurricanes. Two to five of those will be Category 3 or higher.

“That’s pretty much a safe bet every single year until the sea surface temperatures cool off,” said Barry Keim, Louisiana state climatologist.

Current ocean conditions are in the warmer cycle of the Atlantic Multidecadal Oscillation.

In this cycle, ocean surface temperatures in the north Atlantic Ocean go up or down by as little as 1 degree and influence the number and strength of hurricanes, he said.

The last “warm” spell in the cycle was from 1945 to 1969, then the ocean surface temperature cooled again to usher in a few decades of much fewer and weaker hurricanes.

The north Atlantic Ocean is about 12 years into one of the “warmer” cycles. Until that turns around, a higher-than-average number of storms should be expected during hurricane season, Keim said.

The exception would be during years when El Niño occurs.

El Niños increase upper atmosphere winds and essentially “cap” hurricane formation, while the opposite occurs during a La Niña, he said.

There is a weak La Niña occurring now, Keim said.

“It creates a very hospitable environment for hurricanes to vent in the upper atmosphere,” he said. 

It’s likely that this La Niña effect will continue at least through the early part of hurricane season, Keim said, but it’s  not known how long those conditions will last.

Although the formation of storms has been above average, the last two years were relatively quiet for the United States and especially the Gulf of Mexico coast, Keim said.