Forecasters with the National Oceanic and Atmospheric Administration and its Climate Prediction Center have raised the likelihood for a below-normal season for the rest of the Atlantic hurricane season.
Their updated outlook predicts a 70-percent chance of a below-normal season, a 25-percent chance of a near-normal season, and only a 5-percent chance of an above-normal season. The probabilities in their May 22 outlook were 50 percent, 40 percent and 10 percent, respectively.
Normal is the 30-year seasonal average of 12 named storms, six hurricanes and three major (category three or higher) hurricanes. This update predicts a 70-percent likelihood of seven to 12 named storms (top winds of 39 mph or higher), including three to six hurricanes (top winds of 74 mph or higher), of which zero to two could become major hurricanes (winds of at least 111 mph).
The primary factors influencing the increased chance of a below-normal season are listed below:
1) Overall atmospheric conditions are not favorable for storm development.
2) Overall oceanic conditions are not favorable for storm development.
3) The El Nino circulation pattern in the Pacific Ocean is still likely to develop and to suppress storm development by increasing vertical wind shear, stability, and sinking motion in the atmosphere.