Forecasters said warmer-than-normal sea surface temperatures and wind patterns that favor storm formation mean chances are higher for an above-normal season. However, that is tempered with the expected development of an El Nino weather pattern over the Pacific may suppress storms later in the season.
The season so far has produced four tropical storms and two hurricanes. Twelve to 17 tropical storms were expected with as many as five to eight hurricanes, compared to a normal Atlantic season that produces about a dozen named storms, forecasters said. A couple could become major hurricanes with winds of 111 mph or higher.
Last year was one of the busiest seasons on record with 19 named systems, including Irene, one of the costliest storms in U.S. history.
The high activity in the Atlantic has been happening since 1995 because of the right ocean and atmospheric conditions, said Gerry Bell, the lead seasonal forecaster at NOAA’s Climate Prediction Center.
Early-season activity in the deep tropics off Africa’s coast, which produced Ernesto and Tropical Storm Florence early this month, also generally indicates a more dynamic season, Bell said.
“Conditions are more conducive right now, but we expect them to become less favorable if El Nino develops as expected,” Bell said.
El Nino, which is expected to form this month or in September, warms Pacific waters near the equator and increases wind shear over the Atlantic, tearing storms apart. The peak of the Atlantic hurricane season runs from August through October.
“We have a high confidence that El Nino will develop this month or next, but also that its influence will be delayed until later in the season,” Bell said.
The Atlantic hurricane season got off to an earlier-than-official start this year when Tropical Storm Alberto formed May 19 off the South Carolina coast.
Forecasters name tropical storms when their top winds reach 39 mph; hurricanes have winds of at least 74 mph.
No major hurricane has made a U.S. landfall in the last six years, since Hurricane Wilma cut across Florida in 2005. This August marks the 20th anniversary of Hurricane Andrew’s catastrophic landfall in South Florida as a Category 5 storm.