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Car takes on floods. (Photo D. Allen Covey / Courtesy VDOT)The Science Behind the Storms

By Kyle Orland
Maryland Newsline
Thursday, Nov. 13, 2003

1. Why do most hurricanes in the Northern Hemisphere move from east to west?

Answer: Because the tropical trade winds blow from east to west. The same trade winds that brought many explorers to the new world push most Northern Hemisphere hurricanes from east to west.

(Source: The Straight Dope)


2. Fill in the blank: Doubling the maximum wind speed of a hurricane will _________ the damage the hurricane does.

Answer: More than double. Potential damage for a hurricane generally increases exponentially with wind speed, so doubling the windspeed more than doubles the potential damage. A hurricane with a maximum wind speed of 148 mph could do up to 250 times more damage than a hurricane with a 74 mph maximum wind speed!

(Source: NOAA's Hurricane Research Division)


3.  What are the main conditions needed for a hurricane to form?

Answer: A cluster of tropical thunderstorms combines with warm, moist ocean air. Warm sea waters heat the air above them, creating a column of low pressure and moist air that is twisted by the rotation of the earth underneath it. Eventually, the rising moisture cools to form the towering, spiraling clouds that are the start of a hurricane.

(Sources: United Kingdom Met Office, University of Illinois)


4. Why does a hurricane’s intensity decrease rapidly over land?

Answer: Because the land is rougher, cooler and not as moist as the ocean. Once a hurricane makes landfall, it can no longer draw heat and moisture from the ocean, which makes it hard to maintain the area of extremely low pressure needed to sustain the center of the storm.

(Sources: NOAA's Hurricane Research Divison, Texas A&M Meteorology Department)


5.  Which of the following is NOT a major difference between a hurricane and a land-based cyclone?

Answer: A land-based cyclone can't reach hurricane-force wind speeds. Land-based cyclones can be just as windy and powerful as hurricanes. A hurricane is a tropical cyclone that forms over the ocean during the summer or fall.

(Source: Western Michigan University)


6.  Which of the following is NOT used to measure a hurricane’s wind speed?

Answer: An analysis of wave height and storm distance. There are a variety of different methods for determining a storm’s wind speed. In one of the most accurate methods, the National Oceanic and Atmospheric Administration drops wind-measuring instruments called dropsondes into a hurricane from specially designed planes called Hurricane Hunters.  

(Source: WeatherLand)

7.  What is the expected maximum sustained wind speed for a class five hurricane—considered the most destructive?

Answer: At least 155 mph.

The Saffir-Simpson scale ranks a hurricane’s destructive potential on a scale from one to five. The ranking, first used in 1971 by Herbert Saffir and later modified by Robert Simpson, uses predicted values for wind speed, barometric pressure and storm surge (how much the coastal water levels will rise) to calculate a storm’s ranking.

(Source: National Hurricane Center)


8.  In what part of a hurricane are the strongest winds found (in the Northern Hemisphere)?

Answer: The “right” side of the hurricane (the northern side for a west-moving storm). This trend is reversed in the Southern Hemisphere.

(Source: NOAA's Hurricane Research Division)


9.  At what sustained wind speed does a tropical storm become a hurricane?

Answer: Once a tropical cyclone’s sustained wind speeds reach 74 mph (or 33 meters per second) it officially changes from a tropical storm to a hurricane. A tropical depression changes into a tropical storm when its sustained wind speed reaches 39 mph.

(Source HowStuffWorks.com)


10.  Which of the following is NOT a positive environmental effect of a hurricane?

Answer: Hurricane winds aid birds in their migration. Hurricanes are best known for their terrible destructive power, but there are positive environmental effects to the storms, too. It can be hard to keep this in perspective, though, especially if you're a bird being blown hopelessly off course by a hurricane's shifting winds.

(Source: The Louisiana Coastal Wetlands Conservation and Restoration Task Force)

Copyright © 2003 University of Maryland Philip Merrill College of Journalism

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