Eyewall (noun, “EYE-wall”)
This is a ring of intense rain and wind that swirls around the calm center of a tropical cyclone. These powerful storms develop over warm ocean waters just north and south of the equator. They have different names in different regions of the world. Tropical cyclones are “hurricanes” when they occur in the western Atlantic and eastern Pacific north of the equator. They’re “typhoons” in the western Pacific, and “cyclones” south of the equator. All tropical cyclones are destructive storms that have spinning bands of wind and rain. At the center, there’s a calm spot called the eye. Surrounding the eye are the strongest storms of the hurricane or cyclone — the eyewall. The eyewall gets its name because the clouds often pile up higher around the eye. This creates a wall of clouds around the eye when the storm is seen from above.
When ocean waters get warm, they warm the air above them, too. That warm air rises up, leaving an area with low pressure below it. Cooler air rushes in to the space and begins to warm. As the warm air rises, it cools and forms clouds — which produce wind and rain. The clouds grow as more warm air comes up, and the system begins to spin. The spinning creates a calm eye in the middle of the storm. The clouds around the calm eye will have the fastest spin, piling up clouds around the calm center and creating the eyewall.
In a sentence
Scientists use the wind speeds in the eyewall of a tropical cyclone to judge its intensity.