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Salt Lake Community College
Geography 1700 – Natural Hazards
Student Name ___________________________
Quiz #4 – A. J. Allred, Adjunct Instructor
1. During a vigorous mid-latitude cyclone, sometimes called a frontal storm or “wedge” storm, buoyant dry
air will float over heavy, wet air, causing high winds and barometric pressure changes of about 300mb at
any given location.
True ____
False __X__
Dry air is not buoyant compared to wet air. In fact, wet air is chemically lightweight, and rises easily over
cooler, drier air. A barometric pressure change of 300 mb at any given place is impossibly high. A severe
storm can result from a drop in air pressure of 50-75 mb.
See also question #9 below.
2. Which of the following safety options should be most economical for preventing storm damage?
a. Maintain adequate insurance
b. Make a family emergency plan for evacuating and meeting somewhere to count heads
c. Collect emergency supplies
d. Ask the government for more funding
e. Live a safe distance from lakes, rivers and the ocean
Insurance by itself cannot prevent natural hazard damage. Evacuation plans, emergency supplies and
government programs cannot prevent damage either. Living in a safer place is the best way to prevent
damage.
3. Which of the following statements is false?
a. Water is a great source of energy for violent storms.
b. Utah is too far from the tropics to provide enough heat for severe storms.
c. Evaporation of water hides heat that can come back as clouds that release that heat, causing
powerful low-pressure updrafts.
d. Water helps make climate milder, but makes weather less predictable and sometimes dangerous.
e. All natural hazards derive their energy from some form of radioactivity.
All of the statements above are true, except ‘b’. Utah has plenty of its own heat, and needs no heat from the
tropics. Utah typically lacks enough water vapor to produce severe storms. Mountains may hamper
tornadoes at times, but the real shortage is water. With enough heat and water vapor, tornadoes can happen
even in high mountains.
4. Based on class discussion, which of the following combinations best represents a “dry line” storm?
a. 50° F and 45% humidity on one side and 62° F and 55% humidity on the other side
b. 92° F and 68% humidity on one side and 68° F and 65% humidity on the other side
c. 80° F and 55% humidity on one side and 78° F and 50% humidity on the other side
d. 90° F and 52% humidity on one side and 76° F and 50% humidity on the other side
e. 88° F and 80% humidity on one side and 42° F and 54% humidity on the other side
Weather storms are based on rising air that is warm and wet. When cooler, drier air is nearby, warm, wet air
rises more quickly for more severe weather. The most severe combination above involves the strongest
difference between warm & wet versus cool & dry.
Notice that option ‘e’ represents the most humid air adjacent to the most dry and cool air.
See also questions #10 and #12 below.
5. Weather forecasters can now predict tornado touchdowns and hurricane landfalls with great accuracy,
yielding warning times of as much as 11 minutes, compared to just 20 to 25 minutes of warning in the
past.
True ____
False _X___
Forecasters rarely predict anything. Forecast and prediction are fundamentally different processes. When
conditions are right, a ‘watch’ may be issued. When a tornado has been spotted or conditions are extremely
favorable, a ‘warning’ may be issued. Neither a watch nor a warning is a prediction.
6. Stormy weather in North America typically includes what conditions?
a. Rising air
b. Relatively high humidity
c. Tornadic, cyclonic or counter-clockwise winds
d. Ice in high clouds during summer
e. All of the above
Rising air tends to cool and condense vapor back into liquid, which also releases heat that was latent, or
hidden in the vapor. That release of heat provokes another cycle of rising air and high winds at the ground
surface. Even when ice is encountered at high altitude there is typically still enough latent heat in water
vapor to provoke continued rising air, especially when drier, cooler air is nearby.
Tornadic, or twisting winds in a severe storm move counter-clockwise.
7. Violent winds in mid-latitude tornadic storms are typically associated with:
a. Large amounts of latent heat that cause rapidly descending air
b. Relatively high air pressure and clockwise wind rotation due to Coriolis force
c. Collisions between air masses that differ greatly in temperature and humidity
d. Relatively low atmospheric pressure that causes masses of falling (descending) air
e. All of the above
Mid-latitude cyclonic storms involve latent heat in water vapor that contributes to rising air. Stormy
conditions are mostly about rising air, particularly when more stable air nearby helps rising air move faster.
Low atmospheric results from rising air, not falling (descending) air.
Eventually, a storm weakens and fades when less air is rising and more air is descending.
8. Hurricane storm surge involves high wind, high humidity, high atmospheric pressure and high rainfall.
True ___
False _X__
Low atmospheric pressure results from rising air that is very humid. Rising air provokes high wind. Rising
humid air eventually cools and condenses back into clouds that may produce rainfall.
So, severe storms involve warm, humid air that is lightweight and rises easily and can produce high surface
winds and heavy rain. At the ocean, high wind speed can produce high waves and ocean level that can lead
to upstream inundation (ocean flooding). Heavy rain can cause downstream flooding that combines with
inundation may cause building damage and human deaths by drowning.
9. A hurricane condition would be properly represented by about how much difference in sea level
atmospheric pressure across a region where the storm passes?
a. 15mb
b. 80mb
c. 507mb
d. 1013mb
e. None of the above is a reasonable figure
A drop in air pressure of 80mb is the only reasonable answer. A 15mb pressure drop may provoke a rain
storm or windy conditions, but nothing severe. Answers ‘c’ and ‘d’ are more extreme than ever seen on
earth.
See also question #1 above.
10. Tornadoes are “fueled” by atmospheric water vapor that contains vast amounts of latent heat. Even so,
some of the worst U.S tornado outbreaks occur when snow and ice storms are still occurring nearby.
True _X__
False ___
Stormy weather is based on rising air that is relatively warm and humid. When cooler, drier air is nearby,
warm/wet air can rise faster, provoking faster wind speeds, and even lightning, hail and heavier
precipitation.
See also question #4 above and question #12 below.
11. In 2005, Hurricane Katrina was probably the most anticipated natural disaster in human history. People
who died in Katrina were not necessarily foolish: many of them simply had no means of evacuating.
Others who died had survived previous hurricanes and were complacent.
True _X__
False ___
Everything in question #11 is true about Hurricane Katrina.
12. Blizzards contain substantial amounts of atmospheric heat. Freezing temperatures in a blizzard can
enhance the effect of a nearby fading hurricane or other “extra tropical” storm.
True _X__
False ___
See questions #4 and #10 above. In the United States, springtime can include cold air that remains from
winter, or even snow on the ground nearby when warm, wet air arrives from the ocean. The contrast
between cold/dry and warm/wet can provoke especially severe rising air, with substantial risk of lightning,
heavy rain and/or hail. With severe wind, a tornado may also appear.
13. If U.S. tornadoes tend to track from southwest to northeast, then should public safety services always
provide equal warnings to the broadest possible area anytime a tornado is expected?
Yes ___
No _X__
Public safety officials try to avoid warning people who are not in danger, to help prevent people taking
cover without good reason. If warnings are issued too often, people may become insensitive and fail to
respond when a genuine emergency arises.
The fact that tornadoes tend to move eastward and northward helps public safety officials determine what
areas are most in need of warnings. The process of deciding who to warn is difficult and yet must be done
quickly. Mistakes may occur, especially because tornado movement can change unpredictably. A tornado
may slow down, speed up, or even reverse direction, even though its overall movement is mostly eastward
and a little north as well.
14. Much of the United States and even parts of Canada are not protected from hurricane effects that
originate in the tropics. Even Utah and Arizona can receive precipitation from hurricanes.
True _X__
False ___
A severe storm may lose its hurricane status when it passes over land, but severe weather can continue for
hundreds of miles inland. The dry western United States can also receive moisture from a dissipating storm
that originated over the ocean far away. Even Canada can experience heavy rain from tropical storms move
far enough north and inland.
15. There is a strong negative correlation between the size of a U.S. hurricane or tornado and how often
such storms occur.
True _X__
False ___
Extremely large storms occur only rarely. Very small or minor weather changes can occur almost
everywhere at almost any time. As a general rule, the larger the hazard the less often it occurs.
16. During a tornado or hurricane, isolines for rainfall and air pressure tend to be:
a. Very close together, indicating rapid change in wind or rain
b. Very far apart, indicating rapid change in wind or rain
c. Close together for rain, and far apart for wind
d. Close together for wind, and far apart for rain
e. All of the above is a good description of a severe tornadic storm
Isolines connect points of equal value. Severe storms tend to include rapid drop in air pressure (caused by
rising air) and heavy precipitation.
So, isolines for falling air pressure tend to be close together, showing rapid change. The same is true for
heavy rainfall. These two concentrations of rapid change also tend to be close to each other, because rapidly
rising humid air is likely to also produce heavy precipitation.
17. Storms with lightning and hailstones are caused by greater heat inside a storm center that is surrounded
by less buoyant air. Air inside these kinds of storms is often frozen, even in the summer time.
True _X__
False ___
Ice and snow will appear in the higher parts of tall clouds. Even so, frozen air and water can still be buoyant
if surrounding air outside the storm is even colder and/or drier.
Even on a hot summer day, air aloft will be frozen somewhere high above. Frozen air may not rise as
quickly but can still contribute to stormy conditions below.
18. Which of the following characteristics of the atmosphere is the first factor to begin the process of storing
energy for a tornado, hurricane, blizzard or other severe storm:
a. sunshine
b. wind
c. rain
d. humidity
e. evaporation
Energy for stormy weather comes from solar rays. A large portion of solar energy is in the form of
sunshine.
Heat and pressure result when solar energy is absorbed. Heat causes evaporation of water and storage of
latent heat that can cause severe weather later on.
19.
Mid-latitude storms have which two conditions that make them capable of greater severity than simple
convective storms in the tropics?
a. More heat and more humidity
b. Great contrast in heat and humidity between air masses, and Coriolis effect
c. More heat and less Coriolis effect
d. More humidity and high elevation above sea level
e. More heat and less humidity
Heat and humidity are present in nearly all stormy weather. Storms can be more severe when warm, humid
air collides with drier, cooler air, resulting in faster wind speeds and more likelihood of lightning and
hailstones.
20. Which of the following statements regarding water vapor is true?
a. Evaporation does the same thing as condensation because both involve water
b. Severe storms erupt as evaporation forms towering high clouds
c. Evaporation in Arizona explains why Arizona is hotter than Alabama, Georgia or Florida
d. Severe storms begin with condensation that absorbs vast amounts of energy
e. Severe storms erupt as condensation releases vast amounts of energy stored in water
Evaporation is the process of ‘hiding’ heat in water vapor. Condensation is the opposite – converting
invisible water vapor back into visible liquid water, releasing latent heat back into heat that we can feel and
measure as higher temperature.
Evaporation does not form clouds; condensation does form clouds. Evaporation does not make Arizona
hotter than Florida. Lack of water makes Arizona hotter than Florida. Florida is cooler because water
absorbs heat by evaporation and clouds provide shade to block the sun.
Condensation does not absorb energy: condensation releases stored energy back into heat we can feel.
Answer ‘e’ is correct. Release of energy stored as latent heat helps wet air rise more rapidly, causing wind
and evaporation.