Professor Paul Thursday - The Cape Verde Hurricane

Hurricanes can form in a wide range of places over the Atlantic Ocean and the Gulf of Mexico during any given season. One of the more common areas that hurricanes form late in the hurricane season is near the Cape Verde Islands off the west coast of Africa. In fact, many of the strongest hurricanes that have struck the US originated in this area. Let's dive into what makes this part of the world a factory for hurricanes.

Oddly enough, the Sahara Desert is partly responsible for this process. During the summer, as the Sahara Desert becomes home to the extreme heat for which it is known, areas to the south along the coast of the Gulf of Guinea and throughout the African steppes head into their rainy season. The juxtaposition of this cooler, wet region and the extreme heat over the Sahara produces a westerly-oriented jet stream known as the African Easterly Jet (because winds are moving from east to west). When this jet stream becomes established, it has the tendency to become wavy as a parade of troughs progress westward from near the Gulf of Guinea out over into the Atlantic Ocean. These disturbances oftentimes emerge in the vicinity of the Cape Verde Islands as they continue their westward progression.

This jet stream stays most active during the months of May through September. In May and June, the troughs that head out into the Atlantic produce some bands of thunderstorms, but they typically fizzle out as they head further west towards the US and Caribbean. This is because the water temperatures over the Atlantic have not become warm enough to support hurricane or tropical storm development yet. However, by late July into October, the water temps of the Atlantic become warm enough for these tropical waves to intensify as they travel west of the Cape Verde Islands. At times, they reach hurricane status as they continue across the 80+ degree waters. Since these types of hurricanes have such an expanse of warm, open waters to traverse before they reach the Caribbean or US, they have the most time to strengthen. Therefore, the strongest hurricanes that form each season are typically Cape Verde hurricanes. During an average season, two Cape Verde hurricanes will occur.