1 Born in West Africa When hot, dry air from theSahara desert meets cooler, moist air from the Sahel region to the south, small storms form.
2- Across the Atlantic Some storms remain small. But a few gather warm ocean moisture, speeding up as they travel west. When bands of these thunderstorms form a swirling pattern, the system is called a tropical depression.
3- Tropical storms and hurricanes An "eye" forms at the storm's center. Winds spin around it. When winds reach 40 miles per hour, the system is called a tropical storm. When winds reach 74 miles per hour, the storm is a hurricane.
4- After the storm Hurricanes weaken over land. Some storms never hit land. Instead, they turn northeast and die out over the Atlantic Ocean.