Experts know why hurricane season off to slow start

- It's got something to do with the Madden-Julian oscillation -- but you knew that, right?

Associated Press
Published Saturday, September 09, 2000

MIAMI-- With the peak of the 2000 Atlantic hurricane season just days away, experts are trying to figure out why a year predicted to be above average is off to a slow start.

They think they have the answer: It's called the Madden-Julian oscillation.

The atmospheric disturbance is flowing across the Atlantic Ocean and combining with a weakening La Nina to suppress hurricane formation.

Since the June 1 start of the season, two hurricanes have formed, causing little damage and one storm-related death.

"The oscillation is a tropical phenomenon that comes by several times during the hurricane season and affects high-level thunderstorm formation,'' hurricane specialist Jack Beven of the National Hurricane Center in Miami said Friday. "But you still can get storms at any time, and people should not let their guard down.''

Experts say that such a mild start is not necessarily unexpected.

"You look back at the last two hurricane seasons in 1998 and 1999 and we had one storm each year (by) the middle of August,'' Beven said. "All of a sudden, the switch got turned on and it was one storm after another.''

Chris Landsea, an expert at the National Oceanic and Atmospheric Administration's hurricane research division on Virginia Key near Miami, agreed that "we really still have to pay attention. These things can still come out of the Caribbean and aim right at us.

Landsea said a weakening La Nina has caused more "vertical shear,'' winds from different directions and altitudes that tear apart hurricanes.

Then there's that Madden-Julian oscillation. The atmospheric wave begins in the Indian Ocean and moves eastward. Usually it dissipates over the eastern Pacific.

"This year, for some reason, it has gotten into the Atlantic a bit and helped to shut things down,'' Landsea said.

But just as the wave has a phase which suppresses activity, it also has a period where it makes conditions more favorable for hurricane formation.

"The enhancing phase is showing up now,'' Landsea said.

The hurricane center and Colorado State University professor William Gray have issued forecasts for at least 11 named storms, seven hurricanes and three major hurricanes this season.

So far, there have been five named storms and two hurricanes, none of them major. The peak of the average season arrives Sunday.

This year's first hurricane, Alberto, whirled away in the north Atlantic to become the longest-lived August tropical storm on record, but it never threatened land.

A minor Hurricane Debby soaked parts of the Caribbean in late August before breaking up over Cuba, first throwing a scare into South Florida. A man in Puerto Rico died when he slipped from his roof while trying to dismantle an antenna.

Another three named storms never reached hurricane intensity.

On the Net: http://www.nhc.noaa.gov/