The 1997-98 record El Nino is expected to dissipate before the most active part of the 1998 hurricane season, but other global climate factors could produce slightly below-average hurricane activity, hurricane researcher William Gray, Colorado State University, Fort Collins, forecasts. He and his colleagues predict nine tropical storms will form in the Atlantic Basin between June 1 and Nov. 30. From those storms, five hurricanes will evolve, and two will go on to become intense hurricanes with sustained winds of 111 mph or greater. On average, 9.3 tropical storms, 5.8 hurricanes, and 2.1 intense hurricanes form annually.
The team's 1998 forecast comes on the heels of a hurricane season in which activity was flattened by the strongest El Nino event on record. Nevertheless, the Atlantic Basin still managed to produce seven tropical storms, three hurricanes, and one intense hurricane.
"Even though El Nino negatively influenced our 1997 hurricane forecast, it is our belief that this event will die before or shortly after the 1998 hurricane season begins." Gray notes. "The most difficult aspect of the 1998 forecast is to determine whether residual effects from El Nino will have any impact on over all hurricane activity. We will have to wait and see."
When El Nino is in place, it produces upper-level westerly winds at 40,000 feet in the tropical Atlantic Ocean that help block hurricane development. Gray and other forecasters watching this El Nino believe these warm water temperatures will be replaced by cold water sometime in the early spring or summer. These cooler water temperatures, or La Nina conditions, help to promote hurricane activity.
Although the strength or weakness of El Nino is a major influence on hurricane activity, other global climate conditions...