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NOVA scienceNOW: Hurricanes

Viewing Ideas

Before Watching

1. Called typhoons in the Western Pacific or tropical cyclones worldwide, hurricanes are destructive natural events that cause major loss of life and property. But what are they and how do they form? Help students learn more about hurricanes by making a chart on the board (or a handout) that includes basic information about them. Discuss the following with students:

   1. What is a hurricane?
   2. What causes it to form?
   3. What are the main parts of a hurricane?
   4. What stages do they go through?
   5. What causes hurricanes to increase in intensity?
   6. How do scientists classify hurricanes?
   7. How long do they last?
   8. How large an area can a hurricane affect?
   9. How many usually occur in a ten-year period?
   10. Describe any beneficial effects of hurricanes.

   Use a world map to explore where hurricanes form and where they travel. (See Links & Books for more information about hurricanes.)

2. Have students research and report on the three major weather events that have happened in their local area. What happened? How long did each event last? What was the impact of each weather event? (Note: They should include a written narrative of any personal experiences they, family, or friends recall.) How does it compare to harsh weather they have read about?

3. Some population centers are susceptible to area-wide hazards that may require evacuation. Hurricanes are just one example of weather-related hazards. Other natural hazards include fire, flooding, earthquakes, and mud slides. Ask students if they know what to do in the case of a disaster. Have them research their local civil defense plan (which outlines a coordinated response to natural and other types of disasters). What hazards have people prepared for? How will citizens get instructions? What are citizens supposed to do? Have students find out what their school's emergency plan is. You might also have them create personal weather emergency plans.

After Watching

1. Florida is in the pathway of many hurricanes. Students have probably seen television news stories showing people preparing their property for the worst. Often before the arrival of these storms, people are asked to leave their homes voluntarily. Many leave, but many others do not. In certain cases, some of the people who stay lose their lives. Tell students that they are residents in a city that is 14 feet below sea level and a hurricane is heading toward the area. What might be some reasons they would leave or stay? (Reasons for not leaving might include not wanting to leave their home, believing that they have taken enough safety precautions such as boarding up their home, or thinking the storm will not be too severe. Reasons they leave usually have to do with the desire to ensure their own and their family's safety.)

2. Settlers built New Orleans on a swamp between the Mississippi River and Lake Pontchartrain. They built a levee around the swamp and then pumped out the water. Los Angeles, on the southern California coast, is a city without a local water supply. Amsterdam, capital of The Netherlands, was built on dikes designed to keep out the North Sea. To say the least, these cities were difficult to build. What purpose might have compelled early settlers to defy such obstacles? Have students research these cities to see why each was established at its location. Is there a common theme among these reasons? (All were located on water, which is an important trade route. Other factors were Amsterdam's excellent farmland and New Orleans' geopolitical interest to France as the location from which they could control the Mississippi and the continent's interior, thereby denying the English access to this region.)

3. Explore with students some of the topographical features of New Orleans to help them understand the dangers the city faces if a strong hurricane hits. How many square miles is the city? How many airports does the city have? How many roads leave the city? How many square miles of wetlands protect New Orleans? How has the size of the wetlands changed over the last four decades? How is the size of the wetlands projected to change over the next 10 years? What are the implications for the city? (See Links & Books for more resources and information.)

4. It's intuitive that there is a relationship between wind speed and wave height—strong winds produce big waves. But is it a simple linear relationship or is it more complex? Have students calculate the center value (mid-point for each range of numbers) in kilometers per hour for the wind speeds given in the table below. (The table below, originally in knots, has been converted into kilometers and miles per hour, so that students can see how these speeds compare. See Links & Books for information on the Beaufort Wind Scale.) Then, have students make a graph by plotting the center values for wind speed (x-axis) against the wave height (y-axis). (See the sample graph below.) Is there a pattern? What relationship is there between wind speed and wave height?

   Beaufort Wind Scale

   Wind Speed		Wave Height	Appearance of Wind Effects
   miles/hour	kilometers/hour	meters	on water
   <1	<1	<0.3	Mirror-like surface
   1-3	1-5	<0.3	Scaly ripples
   4-7	6-11	<0.3	Small wavelets
   8-12	13-19	<0.3	Large wavelets
   13-18	21-29	0.3-1.2	Small waves, numerous whitecaps
   19-24	31-39	1.2-2.4	Moderate waves, many whitecaps
   25-31	40-50	2.4-3.9	Larger waves, many whitecaps
   32-38	51-61	3.9-6.0	White foam streaks off breaking waves, more 3.9 meter than 6.0 meter waves
   39-46	63-74	3.9-6.0	Moderately high waves of greater length, approximately equal numbers of 3.9 and 6.0 meter waves
   47-54	76-87	6.0	High waves, spray may reduce visibility
   55-63	89-101	6.0-9.1	Very high waves with overhanging crests, visibility reduced
   64-73	102-117	9.1-13.7	Exceptionally high waves, foam patches cover sea, low visibility
   74+	>119	>13.7	Exceptionally high waves. Air filled with foam, white sea, visibility greatly reduced

   Source: Based on the Beaufort Wind Scale, National Oceanic and Atmospheric Administration, www.noaa.gov

   

   Now have students explore possible hurricane damage caused by three different wave heights (2 meters, 4 meters, and 6 meters) and their associated wind speeds. They can begin their research with the Beaufort Wind Scale (estimates wind strengths based on observable effects) or the Saffir-Simpson Hurricane Scale (rates hurricane intensity). (See Links & Books for information on both scales.)

Web Sites

Hurricane Features
www.comet.ucar.edu/nsflab/web/hurricane/311.htm
Describes hurricanes and how and where they form, including information on winds, storm surges, and damages.

The Creeping Storm
www.pubs.asce.org/ceonline/ceonline03/0603feat.html
Provides a civil engineering article with detailed descriptions about the location of New Orleans and the probable consequences of a hurricane.

Consequences of Landscape Deterioration
www.coast2050.gov/reports/Chap6.pdf
Reports on the consequences of landscape deterioration on New Orleans and all of Louisiana.

National Weather Service Chicago
www.crh.noaa.gov/lot/webpage/beaufort/
Provides a detailed description of the Beaufort Wind Scale.

Land Beaufort Scale
www.ncdc.noaa.gov/oa/climate/conversion/beaufortland.html
Describes what happens to land conditions as wind force increases.

Knots to Miles Per Hour Conversion Chart
www.ncdc.noaa.gov/oa/climate/conversion/windchart.html
Shows math conversions for knots to mph.

Science and Technology Focus, Ocean in Motion: Waves-Beaufort Wind Scale
www.onr.navy.mil/focus/ocean/motion/waves4.htm
Includes chart that tells wave height and sea conditions as wind strength increases.

Books

Challoner, Jack. Eyewitness: Hurricane and Tornado. New York: Dorling Kindersley, 2003.
Discusses how and where hurricanes and tornados form, along with models, illustrations, and full-color photographs.

Allaby, Michael, and Jackson, Stephanie. How the Weather Works. New York: Readers Digest Association, 1995
Focuses on weather experiments, record keeping, and forecasting techniques.

Lynott, Bob. How Weather Works and Why. Portland, OR: Gadfly Press, 1994.
Introduces how weather works and explains extreme weather phenomena.