class #18: friday, october 8

Class #18 Friday, October 8, 2010

Class #18: Friday, October 8

Chapter 8 Tropical Cyclones

1

Review sheet for test #2

• Test is on Wednesday, October 13• Test covers chapters 6, 7, 8 except for the

material in boxes 6.1 (p.162), 6.2 (pp. 168-9), 6.3 (pp. 176-7), 7.1 (p.196), and 7.2 (p.204).

• Format of the test will be similar to test #1

Class #18 Friday, October 8, 2010 2

Fig. 8-29, p. 235

More about the life cycle of tropical cyclones

• Some go on to become extratropical cyclones in middle latitudes

• In the Western Pacific Ocean, an occasional typhoon will go on to become a supertyphoon. These have sustained winds > 150 miles per hour

• A widening eye usually indicates a weakening of the storm

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More about the life cycle of a tropical cyclone

• On a day to day basis, the intensity of tropical cyclones is influenced by the sea surface temperatures it encounters.

• The hurricane season of 2005 broke many records for tropical cyclones—27 named storms in the North Atlantic

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Fig. 8-30, p. 236

Fig. 8-31, p. 237

How hurricanes cause destruction

• Winds: hurricanes are classified as to wind damage using the Saffir-Simpson scale from 1 (weakest) to 5 (strongest)

• Hurricanes can contain “mini-swirls” that are tornado-sized with even stronger winds than the main hurricane

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Fig. 8-32, p. 239

Table 8-3, p. 240

How hurricanes cause destruction

• The storm surge is the process of wind-induced seawater flooding– Causes 90% of hurricane deaths– Worst at high tide (new and full moon)– Worst with strong winds– Worst with lowest sea-level pressure– Worst with low-lying land– Depends on coastal and underwater shape

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How hurricanes cause destruction

• Rainwater causes flooding • From 1970-2000 more deaths were caused by

flooding than other types of hazards in hurricanes

• Massive flooding can occur with even weak tropical cyclones or tropical storms

• Hurricane rains have some beneficial effects

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Fig. 8-33, p. 241

How hurricanes cause destruction

• Flooding from tropical storm Allison in June 2001 killed at least 20 people and damaged houses with costs near $5 billion

• Allison caused rain in every Gulf and Atlantic state from Texas to Maine

• Allison caused nearly 36 inches of rain in Houston, TX

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Fig. 8-34, p. 242

Forecasting and tracking hurricanes

• The story of Bryan Norcross– Broadcast weather information during

hurricane Andrew in Florida in 1992– Andrew was a category 5 hurricane– Norcross remained on the air when many of the

other stations were off the air– He broadcast forecasts and valuable

information about safety in hurricanes

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Box 8-3, p. 243

Box 8-3, p. 243

Flooding in Hurricane Hugo

Fig. 8-35, p. 244

Fig. 8-36, p. 245

Fig. 8-37, p. 245

Fig. 8-38, p. 246

Long-term forecasting of hurricanes

• These forecasts are less than perfect• They rely heavily on the cycles of El Niño

and La Niño for forecasting in the North Atlantic

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Fig. 8-39, p. 247