The agency cited several factors in calling for a busier season. Vertical wind-shear, the upper-level crosswinds that can prevent storm structures from forming, is lower than normal. The African monsoon, which allows wind patterns to more easily create storms off the continent’s west coast, is stronger. The agency said there’s an increased chance this year will see a La Niña, the cooling in part of the Pacific Ocean that can reduce wind shear over the Atlantic.