Ch12 Review/Critical qq

Why are tornadoes associated with hurricanes?

As a hurricane makes landfall, its surface winds weaken while upper level winds remain strong. Wind shear develops between horizontal winds at the surface with winds aloft, which contributes to tornado development.

What role is played by barrier islands in the hurricane threat to the U.S. Atlantic and Gulf Coasts?

. Many barrier islands in the U.S. have been developed, some with entire cities built on their shores. These locations are particularly vulnerable to the hazards of hurricanes due to their lack of protection from the open ocean. Barrier islands absorb the brunt of hurricane waves and storm surges, providing some protection for coastal beaches and shoreline structures.

10. What is the basis for the Saffir-Simpson Hurricane Wind Scale?

. The Saffir-Simpson Hurricane Wind Scale is primarily based on maximum sustained wind speed.

What are some alternatives to evacuating people from low-lying coastal areas when a hurricane approaches?

. Vertical evacuation, taking shelter on upper floors of well-constructed buildings, may be an alternative in areas where evacuation options are limited.

How is it possible for a tropical storm to cause considerable inland flooding?

A tropical cyclone occurs in a warm and very humid air mass. High precipitable water amounts in the storm system translate into the potential for very heavy rainfall and inland flooding. The flood potential tends to be greatest where topographic relief is great and rainfall is enhanced orographically.

. What three conditions are required for a tropical cyclone to form?

A tropical cyclone requires relatively high sea-surface temperatures, a sufficient Coriolis Effect to initiate a cyclonic circulation, and relatively weak winds in the middle and upper troposphere over oceanic hurricane breeding grounds.

7. What distinguishes a tropical depression from a tropical storm?

A tropical depression has maximum sustained winds of at least 37 km per hr, and a tropical storm has maximum sustained winds of at least 63 km per hr. Once a system is classified a tropical storm, it is given a name.

Describe the recent trend in hurricane frequency in the Atlantic basin. What factors may be responsible for that trend?

Frequency of intense hurricanes in the Atlantic basin has increased over the last half-century. The increase in frequency is due to an increase in sea-surface temperatures in the tropical Atlantic, an amplified ridge that has been in place over the central and eastern North Atlantic, and weaker vertical wind shear in the tropics over the central North Atlantic. The African easterly jet stream has also been more favorable for hurricane development.

Why are Atlantic hurricanes most likely to form in late summer and early autumn—much later than the time of peak incoming solar radiation?

Hurricanes in the Atlantic are most likely to occur in late summer and early autumn because this is when sea surface waters are the warmest. Sea-surface temperatures do not reach their seasonal maximum until 6 to 8 weeks after the date of most intense solar radiation.

Why did the goal of hurricane modification prove unworkable?

New data called into question the working program hypothesis that seeding hurricanes with silver iodide crystals would reduce wind strength. For instance, scientists discovered that eye wall clouds in hurricanes do not contain enough supercooled water for seeding to be effective and changes in eye-wall diameter occur as part of a hurricane's natural evolution.

Describe how the Saharan Air Layer (SAL) influences Atlantic tropical cyclones.

The Sahara air layer inhibits tropical cyclone development over the North Atlantic. The SAL is a mass of dry, dusty, stable air with strong vertical wind shear that suppresses the deep convection required for tropical cyclone development. If a tropical cyclone comes in contact with SAL, convection within the storm diminishes and the system weakens.

Which sector of a landfalling hurricane is responsible for the greatest storm surge?

The greatest storm surge usually occurs on the side of the approaching intense tropical cyclones where the winds are onshore. In the Northern Hemisphere, the highest storm surge typically occurs to the right of the path of the advancing storm's center of lowest surface pressure marked by the eye.

In general terms, compare and contrast the weather in the tropics with weather at middle latitudes.

Weather in the tropics shows little seasonal variation in temperature and moisture, causing little change in surface air pressure. This is opposite from weather at middle latitudes, which varies by season. Fronts and frontal weather do not occur in the tropics due to broad expanses of warm, humid air whereas middle latitude weather is dominated by air masses with different temperature/humidity characteristics separated by weather fronts along which extratropical cyclones occur. Afternoon thunderstorms typically occur in the tropics as a result of intense solar heating.

Contrast the characteristics of a hurricane with those of a typical extratropical cyclone.

a. A hurricane is a warm-core low pressure system that forms in a uniform mass of warm and humid air, has no fronts, and is about one-third the diameter of a typical extratropical cyclone. Hurricanes spend most of their life cycle over the ocean.

Identify and describe the hazards of hurricanes.

a. Hazards of hurricanes are heavy rains and inland flooding, strong winds, tornadoes, and storm surge. Hurricanes may track well inland, causing persisting heavy rains that bring flooding.

What are some of the problems associated with evacuating large numbers of people from low-lying coastal areas when a major hurricane threatens?

a. Hurricanes often have sudden changes in direction or intensity, which is troublesome for those in coastal communities when making decisions about evacuation timing or routes. In some areas, the time required for evacuation may be lengthy, and advanced warning may be needed. Grid lock on highways also causes problems in areas where many people are forced to use the same way out.

Describe the typical weather in the eye of a hurricane.

a. In the eye of a hurricane, air descends, the sky is nearly cloud-free, and winds are light.

What factors contribute to the rapid growth in human population of hurricane-prone regions of the southeast United States?

a. More resort hotels, high-rise condominiums, and homes are being built near the shoreline. Vacation periods and seasonal visitors increase the population of coastal zones throughout the year. An infrequency of major hurricanes during the 1970s and 1980s also gave people a false sense of security, encouraging development of coastal areas.

Why is the U.S. Pacific coast rarely the target of hurricanes?

a. Most hurricanes that form off the Pacific coast of Central America track toward the west, away from the U.S. Also, ocean waters off the U.S. Pacific coast are too cold to sustain hurricanes.

. Why does a hurricane weaken when the system tracks from ocean to land?

a. Once a hurricane moves over land, it begins to dissipate due to a lack of warm, moist air over the ocean needed to sustain a hurricane. Also, winds rapidly diminish because of greater surface roughness (land versus ocean).