A. By June the Caribbean Sea and Gulf of Mexico are warm enough for tropical cyclones (which include cyclones, hurricanes, and typhoons) to form. The warm, moist air rises from the surface, forming clouds as it cools; at the same time, surrounding cooler air quickly takes the warm air’s place, forming a swirling system. Tropical storms do best in the summer, when there is relatively little wind shear (the change in wind direction or speed higher in the atmosphere).

In addition to warm oceans, tropical cyclone development also requires an initial disturbance in the atmosphere. One disturbance is the tail end of cold fronts that are most vigorous during wintertime. Those are responsible for much of the development we see in May and June and at the end of the season in October and November. The second primary source of disturbance is tropical atmospheric waves (changes in temperature, pressure, or wind velocity). Those waves become stronger toward the middle to latter part of the summer.