The landfall of Hurricane Gloria (1985) on southern New England was accompanied by thousands of birds in the eye. Trapped birds are sometimes seen circling in the eye, and ships trapped in a hurricane report hundreds of exhausted birds resting on their decks. People experiencing an eye passage at night often see stars. This sinking air suppresses cloud formation, creating a pocket of generally clear air in the center. This strong rotation also creates a vacuum of air at the center, causing some of the air flowing out the top of the eyewall to turn inward and sink, replacing the loss of air mass near the center. The sharper the curvature and/or the faster the rotation, the stronger the centrifugal force.Īround 74 mph (119 km/h), the strong rotation of air around the cyclone balances inflow to the center, causing air to ascend about 10-20 miles (16-32 km) from the center, forming the eyewall. This straight line momentum leads to an outward pull against the curve of the wind moving around the center of the tropical cyclone. However, as the speed increases, an outward-directed force, called the centrifugal force, occurs because the wind's momentum directs the wind in a straight line. In tropical cyclones, as the air moves toward the center, the speed must increase. Conversely, the farther the hands are from the body the slower they spin. The closer they hold their hands to the body, the faster they spin. One way of looking at this is watching figure skaters spin. In other words, air increases its speed as it heads toward the center of the tropical cyclone. The conservation of angular momentum means that objects will spin faster as they move toward the center of circulation. It is probably related to the combination of "the conservation of angular momentum" and centrifugal force. The cause of eye formation is still not fully understood. An eye will usually develop when the maximum sustained wind speeds go above 74 mph (119 km/h) and is the calmest part of the storm. The hurricane's center is a relatively calm, generally clear area of sinking air and light winds that usually do not exceed 15 mph (24 km/h) and is typically 20-40 miles (32-64 km) across. Tsunami Preparedness and Mitigation: Individuals (You!).Preparedness and Mitigation: Communities. The Positive and Negative Side of Lightning.
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