The Big Ones: How Natural Disasters Have Shaped Us (and What We Can Do About Them)

by Lucy Jones

All storms require a source of energy to keep their water in the air, and the air moving. For tropical cyclones, the source is the air found just over the ocean near the equator. Because this water is warm, so is the air above it, which rises, carrying moisture upward. This leaves less air near the surface, creating areas of lower pressure. This mechanism—warm air rising, lower pressure near the surface—is what sustains a hurricane, and why hurricane season peaks at the end of summer. A hurricane can form only when the water temperature of the top 150 feet of the ocean is at least 80°F, and that is most likely to occur after months of long days heating the ocean.