A hurricane is a powerful tropical storm with sustained winds of at least 119 kilometers per hour. It forms over warm ocean water, where evaporation feeds towering thunderstorms. The Coriolis effect spins the system into a vortex. A calm eye sits at the center, surrounded by the most violent winds.

Hurricanes go by different names. In the Atlantic and eastern Pacific, they are hurricanes. In the western Pacific, typhoons. In the Indian Ocean, cyclones. They are the same phenomenon. The Saffir-Simpson scale rates them from Category 1 to Category 5 based on wind speed. Category 5 storms can exceed 250 kilometers per hour.

Wind gets the headlines, but water kills more people. Storm surge pushes seawater inland, flooding coastal areas. Heavy rain causes flash floods and landslides. Hurricanes also spawn tornadoes. Warming oceans are making storms wetter and more intense, though the total number has not increased. Coastal development puts more people and property in harm's way. Evacuation planning and building codes save lives.

Key features

• Eye and eyewall
• Storm surge
• Saffir-Simpson scale
• Spiral rainbands
• Landfall and weakening