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CDC URE > 7-3 Severe Wx Techniques > Flashcards

7-3 Severe Wx Techniques Flashcards

0
Q

What areas do Storm Prediction Center advisory charts outline?

A

Areas of expected severe weather

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1
Q

Aside from the AF OWS, what agency produces discussions on model output?

A

National Weather Service

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2
Q

What do you physically compare the 00-hour forecast with during the initialization step of the verification, initialization, and verification (VIV) process?

A

Analysis

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3
Q

What action is the FINAL step of the verification, initialization, and verification process?

A

Verify the 12-hour forecast with real-time data for the same time

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4
Q

What INITIAL conditions are models used based upon?

A

Current weather observations

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5
Q

What action is the goal of severe weather analysis?

A

Identify the preconditions that allow storms to become severe

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6
Q

How many minutes do single-cell storms typically last?

A

30 to 60 minutes

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7
Q

Which characteristic is NOT one of the single-cell thunderstorm?

A

Frequent tornadoes

Characteristics: storm motion equal to the mean wind in the lowest 5km to 7km, weak vertical and horizontal wind shear, high winds and hail

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8
Q

Where do multi-cell storms typically regenerate?

A

Along the gust front

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9
Q

Which characteristic is NOT one of multi-cell thunderstorms?

A

Weak directional shear in the lower levels

Characteristics: straight line or unidirectional profile, large hail near downdraft centers, short-duration tornadoes

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10
Q

Which thunderstorm is NOT a type of supercell thunderstorm?

A

Moderate precip

Types: classic, low precip, high precip

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11
Q

What size hail of classic supercell thunderstorms typically produce?

A

Golf ball

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12
Q

Which type of supercell thunderstorm is most commonly found along the dry line of west Texas?

A

Low-precip

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13
Q

Which region is NOT a primary source for air masses?

A

Temperate

Regions: Arctic, Tropical, Equatorial

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14
Q

What letter or symbol is appended to the label of a modifying air mass that is cooler than the ground below?

A

Lower case k

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15
Q

Where is the geographic area known as the “Great Plains” located?

A

Between the Mississippi River and the Rocky Mountains

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16
Q

In what tornado-producing airmass do tornadoes most frequently occur in families, with paths that are commonly long and wide?

A

Type 1, Great Plains type

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17
Q

What factor is evident above the inversion with a type I airmass?

A

Rapid drying

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18
Q

Which type of airmass is tropical in origin and generally warm and moist?

A

Type II Gulf Coast

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19
Q

Which type of airmass has cold air at all levels?

A

Type III Pacific Coast

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20
Q

Which air mass is cold with surface temperatures ranging from 50F to 68F, the relative humidity commonly exceeding 70 percent at all levels up to at least 500 mb, and avg windspeeds of 15 knots at 850 mb and 50kt at 500 mb?

A

Type III Pacific Coast

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21
Q

Which type of airmass feature maritime polar air overrunning continental tropical air between 5000 and 8000 ft above the surface?

A

Type IV Inverted V

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22
Q

What kind of dew-point temperature difference should exist across a dry line?

A

> 10F

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23
Q

What severe weather synoptic pattern’s airmass is typically Type III?

A

Type D, cold core

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24
Q

When does the maximum severe activity occur with a major cyclone?

A

From time of max heating to a few hours after sunset

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25
Q

What wind speeds do you focus on at the 200 and 300 mb level for severe weather analysis?

A

86 knots

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26
Q

In straight line flow, what quadrants are the main diffluent areas of a jet max?

A

Left front & right rear

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27
Q

Which quadrant in the jet max should you look for positive vorticity advection?

A

Right rear

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28
Q

At which pressure level is strong wind needed for thunderstorms to become severe?

A

500 mb

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29
Q

What does positive vorticity advection indicate?

A

Divergence or upward vertical motion

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30
Q

What parameters are the two MOST important to analyze at 700 mb?

A

No-change line and dry-air intrusion

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31
Q

What weather characteristic does the 700 mb no change line usually line up with?

A

850 mb warm ridge

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32
Q

Which zone is NOT a type of surface convergent zone?

A

Land breeze front

Types: Sea breeze front, dry line, frontal boundary, outflow boundary

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33
Q

How far ahead of a cold front do pre-frontal squall lines form?

A

50 to 150 statue miles

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34
Q

What does a >+1 on the Showalter stability index suggest?

A

Moderate stability

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35
Q

What does a lifted index (LI) greater than 0 indicate?

A

Stability

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36
Q

What weather occurrences does a severe weather threat index if 650 indicate?

A

Tornadoes nearly always occur

37
Q

What atmospheric event does a negative convective available potential energy indicate?

A

Downward vertical motion

38
Q

What weather feature is commonly found south of the center of a low pressure system and is indicated by a relatively cloud-free region?

A

Dry slot

39
Q

Which atmospheric occurrence is NOT a type of lifting mechanism for convection?

A

Decompression

Types: convection, frontal lifting, orographic lifting

40
Q

What number of feet MUST the freezing level be for most precip to reach the surface as snow?

A

1200 ft

41
Q

For the WSR-88D to generate a base reflectivity product, the antenna must complete

A

One elevation slice

42
Q

Which decibel (dBZ) value is considered the approximate precipitable/non-precipitable threshold?

A

+18 dBZ

43
Q

What does the line echo wave pattern (LEWP) signature mean to a forecaster?

A

A favorable environment exists for severe weather development

44
Q

Embedded thunderstorms are detected by the WSR-88D quite well because

A

It’s 10cm wavelength can see through the stratiform precip

45
Q

Outflow boundaries my be seen on the WSR-88D even when no clouds are present because

A

A gradient in the refractive index due to density differences that exist with the boundary

46
Q

Which product is used in the detection and location of rotating thunderstorms and in determining wind field characteristics?

A

Base radial velocity

47
Q

When the Doppler zero line has a noticeable S-shaped pattern, winds are considered to be

A

Veering with height

48
Q

Which concept should be considered when trying to determine hail size?

A

Strength of the updraft

49
Q

The spectrum width product is most effective when

A

Used with other products

50
Q

Which statement is NOT a use of the composite reflectivity product?

A

It can be used to show the 3-D structure of the reflectivity pattern
True: It is the first step in ID sig wx features, quick check on overall reflectivity pattern, instant snapshot of the most important reflectivity features

51
Q

The melting level is displayed on the composite reflectivity product as a

A

Circular pattern of higher reflectivities

52
Q

Vertically integrated liquid (VIL) algorithms display VIL values for storms based on

A

Reflectivity data converted to liquid water content

53
Q

A strongly tilted storm may cause what kind of vertically integrated values to be displayed?

A

Lower

54
Q

The echo tops product is based on data from what other product?

A

Base reflectivity

55
Q

The echo tops product is very useful in

A

Showing the presence of vertical tilt within a storm

56
Q

The storm total precip product provides continuously updated info on precip accumulations within how many nautical miles of the radar?

A

124 nautical miles

57
Q

A limitation of the storm total precip product is that it

A

Has trouble either small-scale features

58
Q

What is an advantage that the user selectable precip product provides over the storm total and three-hour precip products?

A

Gaps of precip will not affect amounts

59
Q

How many hours is the database for the user selectable precip product limited to?

A

30 hours

60
Q

The MAX number of hours that the user selectable precip product can be generated for is

A

24 hours

61
Q

What number of nautical miles is the optimum effective range of the mesocyclone detection algorithm?

A

65 nm

62
Q

Why is tornadic vortex signature detection beyond 55 nm difficult?

A

Beam broadening

63
Q

The inputs to the velocity azimuth display algorithm are

A

Mean radial velocity and base reflectivity

64
Q

The VAD winds profile provides

A

A time-height profile of wind velocity at a pre-determined range

65
Q

Data thresholds for the VWP can be changed

A

By unit control panel

66
Q

The VWP displays

A

The true wind speed and direction

67
Q

The MAX number of VWP that can be displayed on a single VWP is

A

11

68
Q

The VWP can detect features such as

A

Wind shifts and jet streams

69
Q

If the velocity azimuth display (VAD) finds no difference between the zero velocity line and the zeroth harmonic, then the offset is zero, and the wind field is

A

Uniform

70
Q

The color-coded root mean square of the displayed velocity azimuth display winds us related to what characteristic of the winds?

A

Reliability

71
Q

The storm relative mean radial velocity map and storm relative mean radial velocity region product depends on what algorithm?

A

Storm-tracking

72
Q

Resolution of cross-section products

A

Remain constant

73
Q

In clear-air mode, the reflectivity cross-section is used to determine

A

The freezing level

74
Q

The range of a velocity cross-section is limited to

A

124 nm

75
Q

Which data collection limitation of the reflectivity cross-section product causes reduced values at long ranges?

A

Beam broadening

76
Q

A velocity cross-section limitation causing small features at long distances to go undetected is

A

Beam broadening

77
Q

What is an important thing to keep in mind when requesting a velocity cross-section?

A

It must be either parallel, or perpendicular to, a radial

78
Q

The storm cell centroid algorithm performs BEST when

A

Isolated, well-defined thunderstorms are present

79
Q

The storm track information product algorithm provides data on

A

Past, present, and future positions of thunderstorms

80
Q

What determines the length of a forecast made by the storm position forecast algorithm?

A

Accuracy of previous volume scan’s forecast

81
Q

The MOST important product used in defining storm segment is

A

Base reflectivity

82
Q

Which statement best defines a storm cell segment?

A

Contiguous sample volumes along a radial that are greater than or equal to specific reflectivity thresholds

83
Q

The three estimates the hail detection algorithm provides are probability of

A

Hail, probability of severe hail, and max expected hail size

84
Q

The probability of severe hail algorithm will look for hail greater than

A

3/4 inch

85
Q

What info needs to be routinely updated to increase the hail detection algorithm’s performance?

A

Mean sea level altitudes for 0C and -20C

86
Q

Which product provides info on cell-based vertically integrated liquid, height of max reflectivity, and max reflectivity in the cell?

A

Storm structure product

87
Q

What info does the cell trends product provide the forecaster?

A

Status of supercells and the potential for microbursts

88
Q

What agency developed the WSR88-D product/phenomena matrix?

A

Air Weather Service

89
Q

What product is BEST used to isolate storms associated with heavy snow showers?

A

Vertically integrated liquid

CDC URE (9 decks)

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