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AT325 > Thunderstorms and Radar > Flashcards

Thunderstorms and Radar Flashcards

1
Q

Other than the power control, the most important control on an airborne radar is the:

A

tilt control

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2
Q

Airborne weather radar typically has what wavelength? Ground Based Radar has what wavelength?

A

3 cm and 5cm respectively

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3
Q

The longer the wavelength of radar utilized, the larger:

A

the diameter of the antenna used

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4
Q

If you wanted to be able to “see” cloud droplets (not preceipitation) on an airborne radar, would a smaller or larger wavelegth work better?

A

smaller (around .5cm)

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5
Q

The intensity of the radar signal returned froma weather “target” is a function of what?

A
  1. droplet size
  2. droplet number density
  3. composition of the hydrometeors
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6
Q

With respect to radar beam width, greater accuracy occurs (at fixed wavelength) with a narrow beam, wide beam, or medium beam?

A

narrow beam

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7
Q

Range resolution refers to the ability of radar to what?

A

distinguish between two targets the same direction from the radar, but at different distances

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8
Q

In order to show as two separate targets, echoes must be separated by at least how many beam widths?

A

1 beam width

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9
Q

Attenuation is any process that what?

A

reduces the power density of a radar beam

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10
Q

Precipitation attenuation is worst for which band of radar?

A

x-band radar

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11
Q

Range attenuatation is normally proportional to what”

A

the inverse of the square of the distance to the target

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12
Q

a radar shadow occurs when what happens?

A

rain attenuates the signal so strongly that insufficient energy is returned to the radar receiver to be displayed

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13
Q

The fundamental difference between the echo image of a non-severe storm and that of a severe storm is that the sever storm will exhibit what?

A

scalloped contour outlines

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14
Q

You should avoid thunderstorms by what distance, when flying above the freezing level?

A

20 nm

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15
Q

You should avoid thunderstorms by what distance, when flying below the freezing level?

A

10 nm

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16
Q

The danger of flying into a radar shadow (on airborne radar) is what?

A

there may be undetected thunderstorm activity in the area of the radar shadow

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17
Q

A hook echo on a radar scope is the signature of what?

A

a mesocyclone

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18
Q

If a thunderstorm possesses a hook echo, in what quadrant of the storm would you expect to find it?

A

southwest

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19
Q

Do all tornadic thunderstorms exhibit a well-defined hook echo?

A

no

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20
Q

doppler radar measures what exactly?

A
  1. radial velocity relative to the radar antenna
  2. velocity shears
  3. areas of likely turbulence
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21
Q

What is a BWER?

A

bounded weak echo region, which is an area of low reflectivity radar returns, surrounded by high reflictivity returns, signifying an area of strong updrafts

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22
Q

What does TVS stand for?

A

tornado vortex signature

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23
Q

Stormscope and strikefinder detect what”

A

lightning discharges

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24
Q

What are some strengths of spheric detectors, compared to airborne radar (lightning detectors)

A

lower cost, easier to use, little or no precipitation attenuation, and it can be used safely on the ground

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25
Q

What are some weaknesses of spheric detectors compared to radar?

A

they are less precise than un-attenuated radar, can’t show precip not associated with a thunderstorm, they experience aliasing of pixels toward the aircraft position, particularly when severe thunderstorms are present

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26
Q

Most damage due to sever thudnerstorms is concentrated in which region of the US?

A

Central plains and east of mississippi river

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27
Q

What are the national weather service criteria for a severe thunderstorm?

A
  1. hail with diameter 1 in or greater, or
  2. wind damage or wind gusts greater than 58 mph, or
  3. a tornado
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28
Q

What is necessary for the formation of a thunderstorm?

A
  1. source of moisture
  2. conditionally unstable atmosphere
  3. a mechanism to trigger an updraft
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29
Q

In addition to the basic requirements, what additional requirement is necessary for a severe thunderstorm to occur?

A

strong vertical wind shear

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30
Q

Out of the three requirements of a thunderstorm, which is least responsible for how the storm organizes?

A

amount of moisture present

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31
Q

A front, terrain features, outflow from another t-storm, and differential heating of air over surfaces with different properties are all likely to create a boundary that could result in the lifting necessary to produce a t-storm. T/F?

A

True, a strong updraft however is not likely to create one

32
Q

What spatial scale does the term “mesoscale” refer to?

A

a few to a few hundred kilometers

33
Q

What type of t-storm always rotates?

A

supercell t-storm

34
Q

what type of t-storm has an anvil?

A

all t-storms have anvils

35
Q

What type of t-storm can have an overshooting top>

A

all t-storms can have an overshooting top

36
Q

What develops when cool air generated by evaporation of rain within the downdrafts spreads outward away from the t-storm after reaching the surface?

A

gust front

37
Q

What is the term used to describe the bulge at the top of a t-storm caused by strong updrafts?

A

overshooting top

38
Q

What term describes the accumulation of rain-cooled air near the surface, under a t-storm

A

cold pool

39
Q

What t-storm feature typically forms over the gust front as warm air is lifted?

A

shelf cloud

40
Q

Most t-storms do not extend very far into the stratosphere, why?

A

because the air in the stratosphere is stable

41
Q

A downdraft in a t-storm does what?

A

results from the drag created by falling precipitation particles, and is enhanced by evaporational cooling

42
Q

A thunderstorm’s anvil is composed of what?

A

ice crystals

43
Q

where do airmass t-storms tend to occur?

A

in environments where the winds do not increase substantially with height

44
Q

Where and when would you most likely see an airmass t-storm?

A

far from any frontal boundaries, 4:00 PM

45
Q

what is the primary mechanism that triggers the updraft of an airmass t-storm?

A

solar heating of the surface

46
Q

Why is wind shear a key environmental condition for severe t-storm formation?

A

Strong winds cause the updraft to tilt and separate from the downdraft, allowing the inflow of warm, moist air to continue to feed the storm.

47
Q

What type(s) of t-storms contain thunder and lightning?

A

All thunderstorms

48
Q

What type of thunderstorms form far from frontal boundaries?

A

airmass t-storms

49
Q

what type of t-storms appear as hook shaped echoes on radar reflectivity?

A

supercell t-storms

50
Q

What type of t-storms commonly form along the tail of a comma cloud associated with an extratropical cyclone?

A

frontal squall line t-storms

51
Q

what type of thunderstorms appear as a long continuous line on radar reflectivity, extending hundreds of miles?

A

frontal squall line t-storms

52
Q

what type of t-storms account for most of the large, damaging tornadoes and large hail?

A

supercell t-storms

53
Q

What type of t-storms are responsible for much of the summer rainfall on the Central Plains?

A

mesoscale convective system t-storms

54
Q

What type of t-storm has an anvil that can grow to cover an area the size of an entire U.S. state?

A

mesoscale convective systems

55
Q

What type of t-storm has an anvil and may have mammatus clouds on the underside of the anvil?

A

all t-storms

56
Q

What type of t-storms form when a low level jet helps to transport warm moist air into the storm and provides the low-level wind shear that contributes to storm rotation?

A

supercell t-storms

57
Q

What is true about a gust front?

A

it often produces a shelf cloud or a roll cloud, it can trigger new t-storm growth, and it is shallower than a t-storm

58
Q

where is the most common location for a frontal squall line to form?

A

ahead of a cold front

59
Q

what is a typical width of the region of heavy precipitation in an MCS squall line?

A

10 km

60
Q

what is a typical width of the entire precipitation region in an MCS squall line?

A

100 km

61
Q

What type of air is normally introduced into a t-storm by a rear inflow jet?

A

dry air

62
Q

what is the term used to describe eddies that develop on either end of a bow echo?

A

bookend vortices

63
Q

What feature of a t-storm sometimes appears as a fine line of lower radar reflectivity?

A

anvil

64
Q

Which of the following is true near the end of the lifecycle of an MCS?

A

the trailing stratiform region decays, leaving a large area of clouds

65
Q

what is the term used to describe the rotating region of slowly spinning clouds associated with MCS dissipation?

A

mesoscale convective vortex

66
Q

When viewing an infrared satellite image, a large, semi-circular or obling region of high clouds covering the entire state of Missouri on a July evening is most likely what t-storm system?

A

mesoscale convective system

67
Q

Along what type of front do frontal squall lines rarely form?

A

warm front

68
Q

how long is a typical frontal squall line?

A

several hundred miles

69
Q

how long does a typical frontal squall line last?

A

hours to days

70
Q

how strong can the updrafts of a supercell t-torm be?

A

approximately 100 mph

71
Q

What term is used to describe the rotating updraft within a supercell t-storm?

A

mesocyclone

72
Q

On what side of a supercell t-storm is the updraft typiclly found?

A

southwest

73
Q

what is the typical diameter of the updraft of a supercell t-storm?

A

3 to 6 miles

74
Q

which statement regarding a wall cloud is not correct?

A

it develops when the cold pool lifts warm air

75
Q

What order do you observe precipitation of a t-storm moving southwest to northeast over you?

A

virga, light rain, moderate rain, heavy rain, hail

76
Q

What features of a supercell t-storm can produce an outflow boundary and gust front?

A

forward flank downdraft, and rear flank downdraft

77
Q

In a strong t-storm, you can identify the location of the updraft by looking for what structural feature?

A

rain-free base

AT325 (6 decks)

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