Colorado State University (CSU) forecasters have lowered expectations for Atlantic hurricane activity through mid-August, assigning an 80% probability that activity will remain below normal from Aug. 5 through Aug. 18.
The university’s forecast calls for less than 2 units of Accumulated Cyclone Energy, or ACE, during the two-week period. ACE measures the combined strength and duration of tropical storms and hurricanes. Researchers placed the probability of near-normal activity at 15% and above-normal activity at 5%.
The quieter outlook comes as the Atlantic has no active tropical cyclones and the National Hurricane Center is not monitoring any areas for potential development during the next seven days. Global forecasting models also show only weak indications of tropical cyclone formation through Aug. 18.
Forecasters attributed the reduced expectations largely to atmospheric conditions that are unfavorable for storm development. Strong El Niño conditions are expected to produce elevated vertical wind shear across the tropical Atlantic. Wind shear can disrupt a developing storm’s circulation and prevent thunderstorms from organizing around its center.
The Madden-Julian Oscillation, a large-scale pattern of tropical rainfall and atmospheric circulation, is also forecast to strengthen over the tropical Pacific. That positioning typically suppresses Atlantic hurricane activity. European forecasting models project well-above-normal wind shear across the Atlantic’s main development region during the coming weeks.
The forecast period normally marks the beginning of the seasonal increase in Atlantic storm activity, which typically accelerates through August before reaching its climatological peak in September.
The university’s broader seasonal forecast also calls for a below-average Atlantic hurricane season.