Weather and Climatology Chapter 9

Why is the weather associated with a cold front usually of short duration?

The slope of the front is relatively steep so the rising motion occurs in a narrow band and the rate of advance is fairly fast.

Approach of a cold front, a warm front, or both: Pressure falls when front approaches

both

Approach of a cold front, a warm front, or both: Warm air is lifted over cold air

both

The FIRST sign of an approaching warm front is the appearance of nimbostratus clouds. (t/f)

false

The term cyclogenesis refers to the decay of a cyclone. (t/f)

false

The winds in an anticyclone generally all blow from the east. (t/f)

false

When surface cyclones form, they almost invariably occur just ahead of an upper air ridge. (t/f)

false

A dryline causes uplift to occur because:

the lifted air mass is moister than the intruding air mass.

Which phase of the midlatitude cyclone's life cycle is associated with a cold-type occluded front?

the phase just prior to the dissipation of the storm

Typically, upper-level air flow is slower over anticyclones than over cyclones. (t/f)

true

When a warm front passes, temperature rises and the wind usually shifts. (t/f)

true

A wind shift in a clockwise direction, as from south to west, is termed ________ wind shift.

veering

The modern view of cyclogenesis, updated from traditional polar front theory to provide a better three-dimensional view, is known as:

the conveyor belt model

warm air -----------> ______________/ _______________/ _____________/ <---------- cold air the diagram above shows a _______ front.

warm

Approach of a cold front, a warm front, or both: Cirrostratus clouds followed by altostratus

warm front

Approach of a cold front, a warm front, or both: Long lasting, steady rainfall

warm front

What type of occluded front is most common along the west coasts of continents?

warm-type occluded front

When the center of a mature wave cyclone passes to the south, you should expect:

winds shifting from east to north and heavy precipitation.

If you were 200 kilometers ahead of the surface position of a warm front, you would find the frontal surface at a height of ________ km overhead.

1

The width or horizontal extent of a typical mid-latitude low pressure system would be:

1000km

A warm front is said to exist when: A) advancing warm air overrides retreating cold air. B) moving cold air overrides warmer air. C) warm air pushes underneath cold air. D) invading cold air pushes underneath warmer air.

A) advancing warm air overrides retreating cold air.

Which of the following lists the stages of the mid-latitude cyclone life cycle in the proper order? A) cyclogenesis, open-wave, occlusion, dissipation B) open-wave, occlusion, cyclogenesis, dissipation C) occlusion, dissipation, open-wave, cyclogenesis D) cyclogenesis, open-wave, dissipation, occlusion

A) cyclogenesis, open-wave, occlusion, dissipation

A trough aloft is generally associated with: A) cyclonic flow at the surface. B) convergence of the jet steam. C) clear skies. D) anticyclonic flow at the surface.

A) cyclonic flow at the surface

Rain long foretold, long last; short notice, soon past. The FIRST FIVE words of this weather proverb: A) refer to a warm front. B) refer to an anticyclone. C) refer to the formation of cumulonimbus clouds. D) have no basis in fact. E) refer to a cold front.

A) refer to a warm front.

Middle-latitude anticyclones in the Northern Hemisphere: A) rotate clockwise. B) travel from east to west. C) have cold fronts but not warm fronts. D) are large low-pressure systems.

A) rotate clockwise.

A midlatitude cyclone forms in western Canada, and very rapidly moves through the Dakotas and passes over the Great Lakes region, bringing very cold temperatures with it. This storm would probably be called a(an):

Alberta Clipper

Why does occlusion lead to the demise of a mid-latitude cyclone?

All of the warm air has been lifted aloft.

In 1921, J. Bjerknes and his co-authors published what came to be known as the polar front theory. Which one of the following statements is correct regarding this theory? A) It was shown to be applicable only to winter storms in the Southern Hemisphere. B) The main features of the theory remain an important part of present-day meteorological thought. C) Although it was useful at the time, it is no longer a useful model. D) The polar front theory was largely incorrect from the very beginning.

B) The main features of the theory remain an important part of present-day meteorological thought.

A ridge aloft is generally associated with: A) cyclonic flow at the surface. B) anticyclonic flow at the surface. C) divergence of the jet stream. D) stormy weather.

B) anticyclonic flow at the surface.

If a warm front is approaching, you can expect: A) falling temperatures. B) rising temperatures. C) clearing skies. D) calm winds.

B) rising temperatures.

Which of these best describes the reason most high pressure systems bring clear skies? A) high temperatures aloft B) sinking air aloft C) rising air aloft D) cold air near the surface E) low temperatures aloft

B) sinking air aloft

The clear skies that separate the head of the comma from the tail in a mid-latitude cyclone are associated with what feature of the storm? A) the warm conveyor belt B) the dry slot C) the mT air mass D) the cold conveyor belt

B) the dry slot

The more violent nature of weather produced by a cold front can be attributed to which two factors? A) the gradual slope and fast forward motion of the front B) the steep slope and fast forward motion of the front C) the gradual slope and slow forward motion of the front D) the steep slope and slow forward motion of the front

B) the steep slope and fast forward motion of the front

A mature mid-latitude cyclone cloud pattern most closely resembles what when viewed from a satellite? A) an octopus B) a starfish C) a comma D) a circle

C) a comma

Which of these is common to both cold and warm fronts? A) divergence of surface winds B) light to calm winds C) lifting of warm air over cold D) decreasing precipitation rates E) steady barometer readings

C) lifting of warm air over cold

The glaze (or freezing rain) that sometimes forms in association with warm fronts occurs when: A) snow melts against a warm surface and later freezes. B) rain freezes as it falls through the air. C) rain strikes a very cold surface and freezes directly to it. D) rain falls during the day and freezes at night.

C) rain strikes a very cold surface and freezes directly to it.

All of the following are common locations for cyclongenesis EXCEPT for: A) the eastern side of the Rocky Mountains. B) the North Pacific. C) the Great Lakes region. D) the Gulf of Mexico.

C) the Great Lakes region.

The lifting of air and the resulting formation of clouds and rain is more gentle (gradual) for a: A) cold front. B) occluded front. C) warm front. D) divergence zone. E) mesocyclone.

C) warm front.

Compared to warm fronts, cold fronts have: A) the same gradient and a faster advance rate. B) the same gradient and the same advance rate. C) a shallower gradient and a slower advance rate. D) a steeper gradient and a faster advance rate. E) a shallower gradient and the same advance rate.

D) a steeper gradient and a faster advance rate.

As a warm front approaches, which progression of clouds are you most likely to see? A) cirrus, cumulonimbus B) altostratus, cirrostratus, stratus, cumulonimbus C) cirrocumulus, cirrus, nimbostratus, stratus D) cirrus, cirrostratus, altostratus, nimbostratus

D) cirrus, cirrostratus, altostratus, nimbostratus

After a cold front passes, which of these does NOT usually occur? A) wind direction shift B) marked temperature drop C) clearing skies D) falling barometer

D) falling barometer

Another common term for the wave cyclone is: A) tropical cyclone. B) polar-front cyclone. C) intertropical convergence zone. D) midlatitude cyclone.

D) midlatitude cyclone.

Surface cyclones move at a speed that is: A) determined by the jet stream. B) a product of the surface pressure gradient force. C) five times greater than the speed of a cold front. D) one-quarter to one-half the speed of the winds at the 500-mb pressure level.

D) one-quarter to one-half the speed of the winds at the 500-mb pressure level.

Middle-latitude cyclones in the Northern Hemisphere: A) have cold fronts but not warm fronts. B) travel from east to west. C) are large high-pressure systems. D) rotate counterclockwise.

D) rotate counterclockwise.

Surface low-pressure systems usually develop in conjunction with a ridge aloft. (t/f)

false

What feature of the upper-level wind pattern must exist for the origin and development of a surface low?

Divergence aloft must be present, usually in conjunction with an upper-level trough.

Explain why divergence in the flow aloft is a necessary condition for the development and intensification of a midlatitude cyclone.

Divergence aloft represents the outflow of air molecules that have been carried up from the surface by the rising air associated with low pressure. When the outflow of molecules at the top is greater than the inflow of molecules at the surface, more molecules will be exiting the low pressure system than are entering. This results in a deepening of the low pressure.

Compared to other types of fronts, the weather associated with a cold front usually: A) covers more area. B) involves less precipitation. C) does not involve thunderstorms. D) is less violent but of longer duration. E) is more violent but of shorter duration.

E) is more violent but of shorter duration.

When speed divergence occurs in the upper atmosphere, what effect does it have on cyclogenesis?

It greatly enhances cyclogenesis by increasing convergence on the surface below.

Surface winds for an anticyclone are convergent. (t/f)

false

Describe the favored locations for surface cyclones and anticyclones with respect to the upper-level ridges and troughs.

Surface lows tend to develop on the downwind side of troughs and surface highs are favored on the downwind side of ridges.

What is the cause-and-effect relationship between the pattern of upper-level winds and surface low- and high-pressure systems?

Upper level wind patterns strongly control the origin and development of surface systems.

The approximate lifetime of a wave cyclone is:

a few days to a week

A blocking high is caused by:

a persistent anticyclone.

On a weather map, a line with blue triangles on one side and red semicircles on the other represents:

a stationary front

The development of major winter storms in the midwest depends strongly on:

air mass contrasts

A ________ cold front occurs when a strong high-pressure circulation brings colder, mP air into the eastern United States from the Atlantic Ocean.

backdoor

A wind shift in a counterclockwise direction, as from east to north, is termed ________ wind shift.

backing

In the United States, the air mass most commonly found at the back of a cold front is:

cP

Which air mass type is generally found on the poleward side of a midlatitude cyclone?

cP

What cloud type is often seen as the first sign of an approaching warm front?

cirrus

On a weather map, ________ fronts are shown with blue triangular points along a blue line.

cold

Severe weather, including tornadoes, is most often associated with a ________ front.

cold

Approach of a cold front, a warm front, or both: An "invading" cP air mass

cold front

Approach of a cold front, a warm front, or both: Severe thunderstorm/tornado

cold front

Approach of a cold front, a warm front, or both: Winds shift from southwest to northwest

cold front

The cloud type most frequently associated with a cold front is:

cumulonimbus

The arrival of a cold front brings: A) mild weather. B) gentle rains. C) higher temperatures. D) cumulonimbus clouds. E) stationary winds.

cumulonimbus clouds

The wind direction in a low pressure system is:

dependent on your location relative to the storm center

Thunderstorms can be generated when a cT air mass meets an mT air mass and creates a frontal boundary called a:

dryline

A front with a surface boundary that is not moving is known as a stable front. (t/f)

false

Cyclones usually form alone, although sometimes they are associated with anticyclones. (t/f)

false

Cyclones usually move fastest in summer. (t/f)

false

Freezing rain and/or sleet occur most often with a cold front. (t/f)

false

Frontal systems cause clouds by adding moisture to the air. (t/f)

false

Generally, a change in wind direction from southwest to northwest means bad weather will come soon. (t/f)

false

Occluded fronts characterize the beginning stages of a middle latitude cyclone. (t/f)

false

Straight west-to-east winds aloft cause maximum cyclone development. (t/f)

false

The general term applied to warm air moving up over a colder air mass is:

overrunning

warm air -----------> ______________/ _______________/ _____________/ <---------- cold air Refer to the diagram of a front shown above. If the warm air at the back is stable, what kind of cloud is most likely to form and produce precipitation in association with the front?

nimbostratus

An approaching wave cyclone would be indicated by a ________ barometer reading.

rapidly falling

The weather most typically associated with a blocking high is:

repeated storms that can lead to flooding in one part of the country.

The energy of a mid-latitude cyclone comes mainly from:

sinking cold air and rising warm air

The life cycle of a midlatitude cyclone generally has ________ stages.

six

Outside of the Great Lakes region, rising barometric pressure and a wind from the northwest generally mean that:

skies will clear.

The type of weather most frequently associated with cold fronts is

thunderstorms and other severe weather

Cold fronts are steeper than warm fronts. (t/f)

true

Cold fronts generally travel faster than warm fronts. (t/f)

true

Cyclogenesis frequently occurs in Colorado. (t/f)

true

Cyclogenesis refers to the birth of a cyclone. (t/f)

true

Cyclones forming over the North Pacific generally travel further southward during the winter. (t/f)

true

Downstream from a ridge aloft, the wind direction is northwest. (t/f)

true

Humid air is less dense than dry air. (t/f)

true

Middle-latitude cyclones quickly die out once all the warm air has been lifted aloft. (t/f)

true

Middle-latitude cyclones typically develop along segments of the polar front. (t/f)

true

Most cyclones and anticyclones are generated by upper-level air flow. (t/f)

true

People usually pay more attention to cyclones than they do to anticyclones. (t/f)

true

Ridges and troughs are features of the upper level wind pattern. (t/f)

true

Speed divergence helps maintain surface lows. (t/f)

true

The region between the warm front and cold front of a wave cyclone is the warm sector. (t/f)

true

Thunderstorms are most common along a cold front. (t/f)

true