Salt Lake Community College
Geography 1010 – Meteorology
AJ Allred, Adjunct
Quiz #9
Note to Question 1: The textbook indicates that a warm front can produce substantial storminess IF
there is a large amount of water available. The result can be substantial instability that can lead to vast
amounts of latent heat release and rapidly rising air. However, notice what the textbook also says
about general differences between cold fronts and warm fronts.
1. Compared to a cold front, the arrival of a warm front should be accompanied by ______
a. Gradual cloudiness, with light to moderate wind and rain over a longer period of time.
b. Intense rain, strong, gusty winds and lightning, hail and severe downdrafts.
c. Much more vertical cloud development, including very tall cumulo-nimbus clouds.
d. Only rain, never freezing rain, hail, snow or sleet.
e. A greater likelihood of tornadoes and damaging micro burst winds than with a cold front.
Note to Question 2: Dry lightning just means a convective storm with rapidly moving air, but not a
great deal of moisture for heavy precipitation. A “dry line” storm is something very different from
just lightning. What does the textbook say is an alternate name for “dry line” storms?
2. A “dry line” storms tends to produce some dry lightning and cloud cover with light winds,
but very little rain due to lack of moisture. Dry line storms can be hazardous, but much less
so than any of the mid-latitude cyclone storm types.
True ___
False ___
Note to question 3: Ask yourself this: Does cold air more easily “fill the bucket” when water is
present? Is hot air “thirsty” and very unlikely to surrender water by reaching vapor saturation,
otherwise called “dew point” or “full bucket”?
3. Which of the following dew point temperatures represents weather during which body
perspiration will not help a person cool off by evaporation?
a. 41ºF
b. 48ºF
c. 82ºF
d. 61ºF
e. 70ºF
Note to question 4: Do ocean regions produce more humidity and moisture for storms than continent
land masses? If so, then what combination below provides the classic dry air collision with wet air?
4. Which of the following air mass collisions is most likely to produce a “dry line” storm that
results in a tornado?
a. mT and cT
b. mT and cP
c. mP and cP
d. cP and cA
e. None of the above. Dry line storms are about dry air, not cold or humid air
Note to question 5. Is Utah possibly the driest state in the United States because it is not located near
any major source of water? Even Arizona has the Gulf of California and Gulf of Mexico. What
happens to moisture in air masses after they pass over hundreds of miles of high mountains? What
kind of terrain lies between Utah and the mP (Maritime Pacific) wet air that passes across the U.S.
west coast?
5. Westerly winds can gradually convert dry, stable cP air from Siberia into cool, moist and
unstable air that brings precipitation to the U.S. west coast. Some of that moisture could
reach Utah, although most of it is typically dropped by orographic precipitation on high
mountains along the way.
True ___
False ___
Note to question 6. A stationary front is not an occluded front. A stationary front is simply not
moving forward along the ground, but air may still be rising, releasing latent heat and precipitation.
In fact, stationary fronts can produced heavy precipitation in one place over time, instead of spreading
precipitation over a wide area along a ground path that is typically toward the east.
6. A stationary front has lost its energy, and precipitation will diminish quickly as clear skies
develop.
True ___
False ___
Note to question 7. The arrival of humid, buoyant air can trigger a severe storm if a collision occurs
with cold and/or dry air. The speed of rising air is directly related to comparative buoyancy and the
speed of potentially damaging surface winds is directly related to the speed of air rising near the
center of a cyclone. The speed of rising air is also closely associated with the size of hailstones and
the separation of electrically charged particles that result in lightning and thunder.
7. A sudden, substantial change in humidity is associated with weather that could result in a
tornado or other severe thunderstorm.
True ___
False ___
Note to question 8. Everything in Question 8 is consistent with mid-latitude cyclones. In Utah, a
developing storm in Utah frequently exhibits this same pattern: an arriving storm begins with an
invasion of warm wind, followed by a sharp drop in temperature and precipitation associated with an
arriving cold front.
8. In Utah, when the weather is changing for a storm, we often say “The wind before the warm
and the warm before the storm.” This pattern results from mid-latitude cyclones in the
United States that often begin with warm air invading cool air, often followed by cold air
wedging underneath warm air.
True ___
False ___
Note to question 9. Everything in Question 9 is true. Sometimes a front is stationary because a
“blocking high” prevents cyclones from their usual migration from west to east. In such cases, there
may be drought under a persistent high-pressure pattern while a nearby low-pressure system produces
excessive precipitation instead of sprinkling moisture along a path.
9. A stationary front can cause flooding because precipitation persists over one area, instead of
being pushed to new areas by either a cold front or warm front.
True ___
False ___
Note to question 10. Mid-latitude cyclones do pivot around a center point. In the northern
hemisphere, the center or interior of a cyclone is always lower pressure, so winds move inward as they
rise. Anti-cyclones turn clockwise, with descending air that presses outward, away from the center.
Westerly winds do not shift to easterlies.
10. In mid-latitude cyclones, the center or pivot point around which winds move is always a cell
of ______.
a.
b.
c.
d.
e.
high pressure flowing outward and rising (rising air is always part of storminess)
low pressure moving inward and clockwise
high pressure air that lifts rapidly and turns counter-clockwise
low atmospheric pressure associated with rising air and counter-clockwise motion
All of the above are possible in mid-latitude cyclones. The difference is whether or not
westerly winds have shifted to an easterly direction or not.
True ___
False ___
Note to question 11. In your experience, does dry snow stick to anything? What happens when
you pass through Utah’s famously powder snow? Utah is dry, isn’t it? So, our mountain-top
snow tends to be made of widely spaced ice crystals with lots of dry air in between. Fluffy, lightweight snow doesn’t stick to anything. On the other hand, liquid water just runs off. What is the
state of water in between powdery-dry frozen snow and wet rainwater runoff? Is there a danger
zone air temperature for an airplane in flight?
11. When air is very humid, which of the following temperatures is probably the most
hazardous to airplanes in flight, and to trees and power lines on the ground?
a 49ºF
b. 18ºF
c. 37ºF
d. -22ºF (minus)
e. -70ºF (minus)
Note to question 12. Mid-latitude cyclones are much more common in the northern hemisphere
because most land mass is north of the Equator. Oceans can host severe storms, but classic
cyclones that mix differing air masses is a phenomenon that is most likely over land, not ocean,
because continental interiors produce severe differences in humidity and heat. Oceans tend to
produce relatively more mild, steady weather due to the ability of water to absorb heat and release,
reducing the swings in temperature that so often occur over land masses. Likewise, vast expanses
of water tend to have much more steady humidity levels, whereas land masses vary widely, from
very dry to humid.
12. Mid-latitude cyclones tend to be more severe in the southern hemisphere due to vast
amounts of ocean heat and the fact that Antarctica is much larger than Greenland. The
contrast between warm ocean and ice-covered land results is heavier snowfall and greater
chill factor. These traits are the trademarks of mid-latitude climates and weather.
True ___
False ___
If you watch the news, golf courses in Utah are often still busy in November while in Colorado
people are shoveling heavy, wet snow from driveways or even roof tops. Why is that?
Colorado borders “tornado alley”. The U.S. Midwest hosts the collision of air masses, with cP
(polar) winds colliding with mT (wet, warm) air, a recipe for severe weather in mid-latitude
cyclones that are characteristic of large mid-latitude continents.
13. Mid-latitude cyclones in the United States tend to weaken as they move through the
western United States. A storm in Oregon will move on toward Utah, and a Utah storm
will move on to Colorado. On reaching Colorado, stormy weather will often______
a. Worsen, because westerly flow is now exposed to conflicting air masses such as cP and
mT. A new source of moisture is now available, and Colorado storms are often much
more severe than in Utah.
b. Diminish, because air continues to dry out by precipitation as it moves west to east.
c. Neither of the above is true, because the westerlies do not exist east of the Rocky
Mountains in Colorado.
d. Neither of the above is true, because westerlies from Oregon to Utah do not continue on to
Colorado due to blockage by the Wasatch mountains.
e. Neither of the above is true, because cT air from Mexico will always prevent development
of ‘dry line’ storms.
Note to question 14. Read this question carefully. Recall which way the two major types of air
flow move across the United States.
14. Trade winds tend to bring warm, moist air from the Pacific Ocean. The result is rain that
begins in Oregon and gradually converts to snow by the time air masses reach Utah.
True ___
False ___
Note to question 15. At night, dry ground easily radiates vast amounts of long-wave thermal
energy back into outer space. If clouds are present at night, then much of that radiation is going to
be absorbed by water and then radiated back to Earth. So, cloudy nights tend to be warmer than
clear skies with bright stars.
Also, ask yourself the difference between “dew point” temperature and “air temperature”. What is
the difference? Does “dew point” mean “full bucket” or “vapor saturation”? If so, then do these
temperatures represent the minimum temperature required for fog formation?
15. Which of the following conditions is most likely to produce ground fog?
a. Air with relative humidity at 40% and weak outgoing surface radiation
b. Air at 68ºF, dew point temperature of 67ºF and strong outgoing surface radiation
c. Air at 22ºF, humidity at 55% and thick cloud cover
d. Air at 41ºF with dew point 50ºF higher
e. None of the conditions above have any chance of producing fog