El Niño causes stronger wind shear, which reduces the number and intensity of tropical storms and hurricanes. El Niño can also strengthen the trade winds and increase the atmospheric stability across the tropical Atlantic, making it more difficult for cloud systems coming from Africa to intensify into tropical storms.
The outlook calls for a 50 percent chance of a below-normal season, a 40 percent chance of a near-normal season, and only a 10 percent chance of an above-normal season. For the six-month hurricane season, which begins June 1, NOAA predicts a 70 percent likelihood of 8 to 13 named storms (winds of 39 mph or higher), of which 3 to 6 could become hurricanes (winds of 74 mph or higher), including 1 to 2 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher).
These numbers are near or below the seasonal averages of 12 named storms, six hurricanes and three major hurricanes, based on the average from 1981 to 2010. The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea and Gulf of Mexico.
“Thanks to the environmental intelligence from NOAA’s network of earth observations, our scientists and meteorologists can provide life-saving products like our new storm surge threat map and our hurricane forecasts,” said Kathryn Sullivan, Ph.D., NOAA administrator. “And even though we expect El Niño to suppress the number of storms this season, it’s important to remember it takes only one land falling storm to cause a disaster.”
Humberto was the first of only two Atlantic hurricanes in 2013. It reached peak intensity, with top winds of 90 mph, in the far eastern Atlantic.
Gerry Bell, Ph.D., lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center, said the Atlantic – which has seen above-normal seasons in 12 of the last 20 years – has been in an era of high activity for hurricanes since 1995. However, this high-activity pattern is expected to be offset in 2014 by the impacts of El Niño, and by cooler Atlantic Ocean temperatures than we’ve seen in recent years.
“Atmospheric and oceanic conditions across the tropical Pacific are already taking on some El Niño characteristics. Also, we are currently seeing strong trade winds and wind shear over the tropical Atlantic, and NOAA’s climate models predict these conditions will persist, in part because of El Niño,” Bell said. “The expectation of near-average Atlantic Ocean temperatures this season, rather than the above-average temperatures seen since 1995, also suggests fewer Atlantic hurricanes.”
NOAA is rolling out new tools at the National Hurricane Center this year. An experimental mapping tool will be used to show communities their storm surge flood threat. The map will be issued for coastal areas when a hurricane or tropical storm watch is first issued, or approximately 48 hours before the anticipated onset of tropical storm force winds. The map will show land areas where storm surge could occur and how high above ground the water could reach in those areas.