BATON ROUGE, LA (WAFB) - The 2015 hurricane season got off to an early start with May's tropical storm Ana, but history tells us pre-season storms like Ana are not always a sign of an active season ahead.
In fact, even with Ana, almost all hurricane forecasting groups are calling for Atlantic storm counts this season to be below-average.
NOAA's late May outlook called for only six to 11 named storms for the coming season with three to six of those as hurricanes, compared to an average of 12 and six, respectively.
So, what is the reasoning behind this season's low-count forecasts? Three key factors at play are expected to slow tropical development.
The first is the presence of El Nino, which is identified by warmer-than-normal sea-surface temperatures over the central and eastern equatorial Pacific. These warm waters change the behavior of the atmosphere overhead and those impacts often translate downstream over the Atlantic basin with enhanced mid- and upper-level winds. Those faster upper-air winds produce shear that works against the growth of tropical systems.
Next is near-normal to cool surface waters over the main development region of the tropical Atlantic. Warm water is the primary fuel for tropical systems and cooler water generally means less energy available.
Third is a seasonal forecast for higher-than-average surface pressures across much of the tropical Atlantic coupled with a tendency for subsidence. Above-average surface pressures and sinking air from aloft are both inhibitors for storm development.
However, even with an outlook for reduced storm numbers, keep in mind that low storm counts don't always mean a reduced storm threat for Louisiana. Audrey in 1957, Betsy in 1965 and Andrew in 1992 all struck during years with eight or fewer total storms.