Atlantic Hurricanes With Dr. Jeff Halverson: Understanding the 21st Century's New Threat
| 26. Question and Answer | |
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| 27. The Death of a Hurricane | |
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This video explains what happens as a hurricane’s life cycle nears its finish. Here we learn about an important concept known as the Bermuda High. This atmospheric phenomenon has a big effect on steering hurricanes toward land or away from it as they approach the United States. + View video + Download Quick Time |
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National Standards: D.1, 5-8; students should develop an understanding of structure of the earth system. D.1, 9-12; students should develop an understanding of energy in the earth system. |
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| 28. Forces That Weaken Hurricanes | |
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When a hurricane is seriously weakened by dry air, cold water or wind shear, the vortex collapses, weakens and spreads over a larger area. Once this happens, the storm can generally not recover. While the peak wind speeds will be less, the area of tropical storm or weak hurricane force winds may expand considerably - which still puts significant populations at risk. + View video + Download Quick Time |
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Media Content: It's unusual for a hurricane to maintain Category 5 status for as many days in a row as Isabel did, and sooner or later there are enough atmospheric and oceanic forces that conspire to weaken a storm. These forces include cold ocean waters, destructive wind shear and dry air blowing off the U.S. continent. + Download media National Standards: E.2, K-4: students should develop understanding about science and technology. D.1, 5-8; students should develop an understanding of structure of the earth system. D.1, 9-12; students should develop an understanding of energy in the earth system. |
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| 29. Bermuda High- Steering Hurricanes | |
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Much of what determines how much hurricane damage occurs in the U.S. in any given year is not just the number of intense storms, but whether atmospheric currents steer these storms into the mainland, or curve them safely out to sea. + View video + Download Quick Time |
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Media Content: What factors cause a storm to be steered into or away from the U.S. coastline? This animation shows a large, permanent high-pressure cell called the Bermuda High pushing hurricanes across the tropical Atlantic from Africa toward North America. Some years, the Bermuda High is located more to the west, over the center of the Atlantic, causing storms to re-curve off the U.S. east coast. They may never make landfall, remaining over open ocean. But in other years, such as 2005, the Bermuda High shifts to the west and south, closer to the U.S. coast. This delays re-curvature until a storm is over Florida, or the Gulf Coast. + Download media National Standards: E.2, K-4: students should develop understanding about science and technology. D.1, 5-8; students should develop an understanding of structure of the earth system. D.1, 9-12; students should develop an understanding of energy in the earth system. |
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| 30. Cold Trails | |
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One storm can impact the intensity of another following closely on its heels. Hurricanes stir up cold water from the abyssal deep. The cold water limits the amount of fuel available to a trailing storm - because evaporation of ocean water is very sensitive to the ocean's temperature. In fact, a temperature change of just a few tenths of a degree Celsius can have a demonstrable impact on storm intensity. + View video + Download Quick Time |
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Media Content: As hurricanes approach the U.S. coast, some will weaken and some will intensify. What happens is very often a function of the ocean surface temperature offshore. Sources of cold water that steal the thunder from hurricanes and weaken them. As this satellite sequence shows, storms leave behind a trail of cold water called a storm wake. In this case, we see first Hurricane Danielle moving up the eastern seaboard, and trailing water that is several degrees cooler. Floyd comes along and crosses behind Danielle's wake. It's likely that Danielle's trail of cold water inhibited the ultimate intensification of Floyd prior to his landfall in North Carolina. + Download media National Standards: E.2, K-4: students should develop understanding about science and technology. D.1, 5-8; students should develop an understanding of structure of the earth system. D.1, 9-12; students should develop an understanding of energy in the earth system. |
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