7-3 Severe Wx Techniques

Question 0

What areas do Storm Prediction Center advisory charts outline?

Answer 0

Areas of expected severe weather

Question 1

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

Answer 1

National Weather Service

Question 2

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

Answer 2

Analysis

Question 3

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

Answer 3

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

Question 4

What INITIAL conditions are models used based upon?

Answer 4

Current weather observations

Question 5

What action is the goal of severe weather analysis?

Answer 5

Identify the preconditions that allow storms to become severe

Question 6

How many minutes do single-cell storms typically last?

Answer 6

30 to 60 minutes

Question 7

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

Answer 7

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

Question 8

Where do multi-cell storms typically regenerate?

Answer 8

Along the gust front

Question 9

Which characteristic is NOT one of multi-cell thunderstorms?

Answer 9

Weak directional shear in the lower levels

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

Question 10

Which thunderstorm is NOT a type of supercell thunderstorm?

Answer 10

Moderate precip

Types: classic, low precip, high precip

Question 11

What size hail of classic supercell thunderstorms typically produce?

Answer 11

Golf ball

Question 12

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

Answer 12

Low-precip

Question 13

Which region is NOT a primary source for air masses?

Answer 13

Temperate

Regions: Arctic, Tropical, Equatorial

Question 14

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

Answer 14

Lower case k

Question 15

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

Answer 15

Between the Mississippi River and the Rocky Mountains

Question 16

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

Answer 16

Type 1, Great Plains type

Question 17

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

Answer 17

Rapid drying

Question 18

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

Answer 18

Type II Gulf Coast

Question 19

Which type of airmass has cold air at all levels?

Answer 19

Type III Pacific Coast

Question 20

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?

Answer 20

Type III Pacific Coast

Question 21

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

Answer 21

Type IV Inverted V

Question 22

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

Answer 22

> 10F

Question 23

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

Answer 23

Type D, cold core

Question 24

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

Answer 24

From time of max heating to a few hours after sunset

Question 25

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

Answer 25

86 knots

Question 26

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

Answer 26

Left front & right rear

Question 27

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

Answer 27

Right rear

Question 28

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

Answer 28

500 mb

Question 29

What does positive vorticity advection indicate?

Answer 29

Divergence or upward vertical motion

Question 30

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

Answer 30

No-change line and dry-air intrusion

Question 31

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

Answer 31

850 mb warm ridge

Question 32

Which zone is NOT a type of surface convergent zone?

Answer 32

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

Question 33

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

Answer 33

50 to 150 statue miles

Question 34

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

Answer 34

Moderate stability

Question 35

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

Answer 35

Stability

Question 36

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

Answer 36

Tornadoes nearly always occur

Question 37

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

Answer 37

Downward vertical motion

Question 38

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

Answer 38

Dry slot

Question 39

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

Answer 39

Decompression Types: convection, frontal lifting, orographic lifting

Question 40

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

Answer 40

1200 ft

Question 41

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

Answer 41

One elevation slice

Question 42

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

Answer 42

+18 dBZ

Question 43

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

Answer 43

A favorable environment exists for severe weather development

Question 44

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

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

Base radial velocity

Question 47

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

Answer 47

Veering with height

Question 48

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

Answer 48

Strength of the updraft

Question 49

The spectrum width product is most effective when

Answer 49

Used with other products

Question 50

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

Answer 50

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

Question 51

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

Answer 51

Circular pattern of higher reflectivities

Question 52

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

Answer 52

Reflectivity data converted to liquid water content

Question 53

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

Answer 53

Lower

Question 54

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

Answer 54

Base reflectivity

Question 55

The echo tops product is very useful in

Answer 55

Showing the presence of vertical tilt within a storm

Question 56

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

Answer 56

124 nautical miles

Question 57

A limitation of the storm total precip product is that it

Answer 57

Has trouble either small-scale features

Question 58

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

Answer 58

Gaps of precip will not affect amounts

Question 59

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

Answer 59

30 hours

Question 60

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

Answer 60

24 hours

Question 61

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

Answer 61

65 nm

Question 62

Why is tornadic vortex signature detection beyond 55 nm difficult?

Answer 62

Beam broadening

Question 63

The inputs to the velocity azimuth display algorithm are

Answer 63

Mean radial velocity and base reflectivity

Question 64

The VAD winds profile provides

Answer 64

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

Question 65

Data thresholds for the VWP can be changed

Answer 65

By unit control panel

Question 66

The VWP displays

Answer 66

The true wind speed and direction

Question 67

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

Answer 67

11

Question 68

The VWP can detect features such as

Answer 68

Wind shifts and jet streams

Question 69

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

Answer 69

Uniform

Question 70

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

Answer 70

Reliability

Question 71

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

Answer 71

Storm-tracking

Question 72

Resolution of cross-section products

Answer 72

Remain constant

Question 73

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

Answer 73

The freezing level

Question 74

The range of a velocity cross-section is limited to

Answer 74

124 nm

Question 75

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

Answer 75

Beam broadening

Question 76

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

Answer 76

Beam broadening

Question 77

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

Answer 77

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

Question 78

The storm cell centroid algorithm performs BEST when

Answer 78

Isolated, well-defined thunderstorms are present

Question 79

The storm track information product algorithm provides data on

Answer 79

Past, present, and future positions of thunderstorms

Question 80

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

Answer 80

Accuracy of previous volume scan's forecast

Question 81

The MOST important product used in defining storm segment is

Answer 81

Base reflectivity

Question 82

Which statement best defines a storm cell segment?

Answer 82

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

Question 83

The three estimates the hail detection algorithm provides are probability of

Answer 83

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

Question 84

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

Answer 84

3/4 inch

Question 85

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

Answer 85

Mean sea level altitudes for 0C and -20C

Question 86

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

Answer 86

Storm structure product

Question 87

What info does the cell trends product provide the forecaster?

Answer 87

Status of supercells and the potential for microbursts

Question 88

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

Answer 88

Air Weather Service

Question 89

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

Answer 89

Vertically integrated liquid