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Question 1

Which of the following statements about perturbations of NWP model initial conditions used in EPSs are correct?

A) They are placed randomly in the model domain.
B) They are determined based on forecast sensitivity to initial condition differences.
C) They are largest where initial conditions are especially uncertain.
D) Their value is generally of similar size to observing instrument errors.

Answer 1

B, C, & D

Question 2

True or False.
A plume diagram for temperature can show multiple solutions for the timing of a cold frontal passage through a model grid box.

Answer 2

True

Question 3

Choose the correct answer in parentheses.

Using the ensemble mean to present the EPS forecast data smooths out (small scale/large scale) features and retains the (small scale/large scale) features. This is the main reason that the ensemble mean forecast generally performs (better than/worse than) the operational forecast in the medium range.

Answer 3

small-scale
large-scale
better than

Question 4

Choose all that apply.

Which of the following statements about EPS spaghetti diagrams are true?

A) Small distances between contours usually indicate small uncertainty.
B) They allow the forecaster to see if there is more than one likely solution.
C) They allow the forecaster to get a sense of the distribution of ensemble forecasts for one or a few contour values.
D) They allow the forecaster to see all contour value(s) of all ensemble member(s).

Answer 4

A, B, & C

Question 5

Choose all that apply.
Which of the following perturbations can be used to make an EPS?

A) Initial conditions
B) Boundary conditions
C) Dynamical formulation
D) Model physics

Answer 5

All dat shit

Question 6

True or False.

A forecaster can use a mean and spread diagram to determine which contour value to choose for a spaghetti diagram.

Answer 6

True

Question 7

True or False.

If none of the precipitation types is forecast by a majority of the ensemble members, the dominant precipitation type is not defined.

Answer 7

False

Question 8

True or False.

One of the biggest challenges in using EPS forecasts is interpreting the post-processed EPS output.

Answer 8

True

Question 9

Choose the best answer.
Buoyancy is a force acting on a parcel of air in response to a difference in _____ causing an air parcel to accelerate _____.

A) density | vertically
B) density | horizontally
C) moisture | vertically
D) moisture | horizontally
E) temperature | horizontally
F) temperature | vertically

Answer 9

A

Question 10

Choose all that apply.
What are the factors that tend to increase buoyancy?

A) Higher vertical wind shear
B) Precipitation
C) Higher water vapor
D) Higher potential temperature
E) Higher cloud water content

Answer 10

C & D

Question 11

Choose the best answer.
The Lifted Index characterizes the amount of instability by lifting a parcel from the surface to _____ mb. A negative LI indicates _____ buoyancy while a positive LI indicates _____ buoyancy.

A) 500 | negative | positive
B) 700 | negative | positive
C) 700 | positive | negative
D) 500 | positive | negative

Answer 11

D

Question 12

True or False.
CAPE is a measure of the potential energy available in the atmosphere and generally can be used as measure of the potential strength of convective updrafts.

Answer 12

True

Question 13

Choose the best answer.

The amount of CAPE in the atmosphere is most influenced by the vertical distribution of _____ and _____.

A) temperature | buoyancy
B) moisture | wind shear
C) wind shear | buoyancy
D) temperature | moisture
E) buoyancy | moisture

Answer 13

E

Question 14

Choose the best answer.

Convective Inhibition (CIN) is a measure of a \_\_\_\_\_, which can prevent an air parcel from reaching its \_\_\_\_\_, thereby preventing convection from occurring.
A) capping inversion | LFC
B) cool layer | LFC
C) capping inversion | EL
D) cool layer | EL

Answer 14

A

Question 15

Choose all that apply.

CIN can be reduced or eliminated by which of the following mechanisms in the lower atmosphere? (6 points)
A) Synoptic scale ascent
B) Heating
C) Synoptic scale descent
D) Moistening
E) Drying
F) Cooling

Answer 15

A, B, & D

Question 16

Choose all that apply.

Which of the following are the primary contributors to downdraft strength?
A) Precipitation loading
B) Updraft strength
C) Amount of moisture in lower atmosphere
D) Evaporation
E) Precipitation type

Answer 16

A & D

Question 17

Choose all that apply.

Which of the following are the primary contributors to the strength of the cold pool and associated wind gusts?
A) Cool pool temperature relative to environment
B) Precipitation type
C) Updraft strength
D) Depth of the cold pool
E) Precipitation rate

Answer 17

A & D

Question 18

True or False.

When vertical wind shear is strong, buoyancy processes are the dominant control on convective updrafts and downdrafts.

Answer 18

False

Question 19

Choose the best answer.

\_\_\_\_\_ dominate(s) early in an ordinary cell’s life cycle and \_\_\_\_\_ dominate(s) in the later stages.
A) Updrafts | downdrafts
B) Downdrafts | updrafts
C) Updrafts | cold pools
D) Updrafts | evaporation
E) CIN | downdrafts

Answer 19

A

Question 20

Choose the best answer.

At midlatitudes, how much low-level shear is necessary to significantly enhance cold pool lifting and cell regeneration?
A) 5 m/s over the lowest 2.5 km AGL
B) 5 m/s over the lowest 5 km AGL
C) 15 m/s over the lowest 2.5 km AGL
D) 15 m/s over the lowest 5 km AGL

Answer 20

C

Question 21

Choose the best answer.

On which side of a cold pool is deep lifting enhanced?
A) Upshear side
B) Downshear side

Answer 21

B

Question 22

Choose the best answer.
How much wind shear is typically necessary for supercell formation?
A) There is no minimum
B) Less than 15 m/s over the lowest 4-6 km AGL
C) Greater than 25 m/s over the lowest 4-6 km AGL
D) Greater than 60 m/s over the lowest 4-6 km AGL

Answer 22

C

Question 23

Choose the best answer.

Wind shear profiles with clockwise curvature, common in the Great Plains, are responsible for producing which kind of supercell?
A) Splitting supercells
B) Dominant left-moving supercells
C) Dominant right-moving supercells

Answer 23

C

Question 24

Choose the best answer.

As a rule of thumb, the optimal state for cold pool lifting occurs when the propagation speed of the cold pool roughly equals the difference between the surface wind and the wind at what level?
A) 0.5 km AGL
B) 2.5 km AGL
C) 4-6 km AGL
D) 10-15 km AGL

Answer 24

B

Question 25

# Choose all that apply. A sheared vertical wind profile leads to which of the following? A) Horizontal vorticity in the atmosphere B) A strong cold pool at the surface C) Updraft tilt

Answer 25

A & C

Question 26

# Choose the best answer. Along the edge of a cold pool, a strong jet of vertical motion results when what conditions are satisfied? A) Regions of positive and negative horizontal vorticity of equal magnitude and size exist in close proximity to each other B) Regions of positive horizontal vorticity of different magnitude and size exist in close proximity to each other C) Regions of positive and negative horizontal vorticity of different magnitude and size exist in close proximity to each other D) Regions of positive horizontal vorticity of equal magnitude and size exist in close proximity to each other

Answer 26

A

Question 27

# Choose the best answer. How much wind shear is necessary to initiate squall lines? A) There is no minimum B) Less than 15 m/s over the lowest 4-6 km AGL C) 15-25 m/s over the lowest 4-6 km AGL D) Greater than 25 m/s over the lowest 4-6 km AGL

Answer 27

A

Question 28

# Choose the best answer. When estimating the shear environment of a squall line, that component of the low-level environmental shear oriented ____________ to the line exerts the most control on the line’s structure and evolution. A) perpendicular B) parallel

Answer 28

A

Question 29

# Choose the best answer. While bow echo and supercell environments have much overlap, supercells tend to have _________ . A) stronger low-level shear (lowest 2-3 km AGL) B) a deeper shear profile (at least 4-6 km AGL)

Answer 29

B

Question 30

# Choose the best answer. How does vertical wind shear influence storm organization? A) By enhancing the ability of a thunderstorm cold pool to trigger new storms B) By decreasing dew point depression at middle levels C) By increasing horizontal vorticity in the updraft

Answer 30

A

Question 31

# Choose the best answer. The strength and organization of boundary-layer-based MCSs ____________ with higher vertical wind shear magnitudes. A) decreases B) increases

Answer 31

B

Question 32

# Choose the best answer. When the updraft column blocks the environmental flow, it creates a dynamic affect of relative ____________of the updraft. A) high pressure upshear and low pressure downshear B) low pressure upshear and high pressure downshear

Answer 32

A

Question 33

True or False. For a given amount of shear, a stronger, more buoyant updraft will not tilt as much as a weaker updraft.

Answer 33

True

Question 34

# Choose the best answer in parentheses. For flow to be geostrophic (rotationally balanced), the Ordinary Rossby Number (advective) needs to be (small/large):

Answer 34

small

Question 35

What is the equation for the Ordinary Rossby Number?

Answer 35

Ro = U/fL ``` U = velocity of the fluid f = Coriolis parameter L = horizontal length scale ```

Question 36

Of what is the Ordinary Rossby Number the ratio?

Answer 36

The local acceleration (U/L) and the Coriolis parameter (f).

Question 37

What 3 influences would make the Ordinary Rossby Number (Ro) larger?

Answer 37

1) decreasing the size of the system (i.e. decreasing the size of L) 2) decreasing the latitude (i.e. decreasing the value of f) 3) increasing the wind speed (i.e. increasing U)

Question 38

What is the equation for the Wave Rossby Number (Rw)?

Answer 38

Rw = c/Lf ``` c = gravity wave speed L = horizontal length scale f = Coriolis parameter ```

Question 39

What is the name of the variable that the Wave Rossby Number is used to derive?

Answer 39

Rossby Radius of Deformation (Lr)

Question 40

What is the equation for the Rossby Radius of Deformation?

Answer 40

Lr = c/f ``` c = gravity wave speed as a function of static stability of the fluid f = Coriolis parameter ```

Question 41

What physical property does the Rossby Radius of Deformaiton formula ignore?

Answer 41

the potential temperature contrast between warm and cold air

Question 42

What is the definition of the Rossby Radius of Deformation?

Answer 42

It is the horizontal scale at which rotation effects become as important as buoyancy effects.

Question 43

When the scale of a weather system is (smaller/larger) than Lr, buoyancy dominates over rotation. What scale does this define?

Answer 43

smaller | the mesoscale

Question 44

When buoyancy dominates over rotation, to what field does the mass (pressure or height) field adjust?

Answer 44

the wind field

Question 45

When buoyancy dominates over rotation, what do gravity waves dominate over?

Answer 45

they dominate over geostrophic flow

Question 46

When rotation dominates over buoyancy, what does geostoprhic flow dominate over?

Answer 46

it dominates over gravity waves

Question 47

When rotation dominates over buoyancy, to what field does the momentum (wind) field respond?

Answer 47

it responds to the mass (height or pressure) field

Question 48

True or False. The maximum size of the mesoscale is essentially whatever the rossby radius of deformation is at that location.

Answer 48

True

Question 49

On what topic was Dr. Blackwell's graduate school dissertation?

Answer 49

tropical plumes in the East Pacific

Question 50

Tropical plumes in the East Pacific form when the length scale of the trough is (less than/equal to/greater than) the Rossby Radius of Deformation. Does this mean that buoyancy or rotation dominate?

Answer 50

Less than. | Buoyancy, bitch.

Question 51

If the magnitude of the positive horizontal vorticity associated with the ambient shear is the same as the magnitude of the negative horizontal vorticity produced along the leading edge of cold air, then the air approaching the cold pool will tend to rise as a ________-________ ____.

Answer 51

vertically-oriented jet

Question 52

The triggering of convective cells is favored along the (upshear/downshear) portion of a spreading cold pool.

Answer 52

downshear

Question 53

True or False. In general, the strongest, most long-lived convective systems will be produced when there is a weak low-level vertical wind shear to balance the cold-pool generated circulation.

Answer 53

False. | Strong low-level vertical wind shear to balance...

Question 54

Hodographs depict the (vertical/horizontal) distribution of the (vertical/horizontal) wind.

Answer 54

vertical | horizontal

Question 55

Points on a hodograph are plotted as a function of what two meteorological variables?

Answer 55

wind direction | wind speed

Question 56

What is the leading edge of the rain-cooled air in the planetary boundary layer called?

Answer 56

the gust front

Question 57

Thunderstorm cold pools are associated with (meso-highs/meso-lows) and may actually be crudely analyzed on a synoptic surface chart.

Answer 57

meso-highs

Question 58

The gust front forms along leading edges of mesoscale domes of rain-cooled air (i.e., surface-layer cold pools) that result from the amalgamation of ______-_______ _________ from individual thunderstorm cells.

Answer 58

evaporatively-cooled downdrafts

Question 59

The gust front is a (pressure/temperature/density/buoyancy/moisture) discontinuity.

Answer 59

density

Question 60

In a gust front, cooler, denser surface air flows outward from the meso-high. As a result, (high/low) θe air is uplifted above the outward-flowing cold pool.

Answer 60

high

Question 61

New convection may form in association with uplift along the gust front if the lifted parcels can reach their _______.

Answer 61

LFC

Question 62

Name 5 characteristics that indicate a gust front passage.

Answer 62

1) Wind shift and abrupt increase in wind speed. 2) Abrupt temperature drop (most of the time). 3) Sharp pressure rise 4) Arc cloud (if boundary layer is moist) 5) Strong vertical wind shear

Question 63

Name the 3 physical mechanisms that control storm structure.

Answer 63

buoyancy processes, gust front processes, and dynamic processes

Question 64

What are 2 buoyancy processes that control storm structure?

Answer 64

1) lapse rates (CAPE) | 2) Moisture stratification

Question 65

True or False. Environmental vertical wind shear affects 1) the ability of the gust front to trigger new convective elements and 2) the ability of the updraft to interact with this environmental shear to produce enhanced, quasi-steady storm structure.

Answer 65

True

Question 66

For a storm, shear is (relative/unrelated) to the motion of the storm.

Answer 66

relative

Question 67

In the absence of suitable shear in a storm's environment, the inflow will be (sufficient/insufficient) to sustain the vigorous updraft that might result from large thermal instability.

Answer 67

insufficient

Question 68

Name 2 gust front processes that control storm structure.

Answer 68

1) strength of the cold pool | 2) strength of low-level vertical wind shear

Question 69

Name 2 dynamics processes that control storm structure.

Answer 69

1) strength of 4-6 km AGL vertical wind shear 2) development of rotational (helical) updrafts and associated favorable vertical pressure gradients on the updraft flank

Question 70

For an ordinary cell, (buoyancy/dynamic processes) is(are) more important in maintaining the updraft.

Answer 70

buoyancy

Question 71

For a supercell, (buoyancy/dynamic processes) is(are) more important in maintaining the updraft.

Answer 71

dynamic processes

Question 72

What are the 3 steps that cause a thunderstorm to develop a rotating updraft?

Answer 72

1) vertical wind shear produces horizontal vorticity tubes 2) tubes are tilted vertically by the updraft 3) thunderstorm rotates in same sense as vertical vorticity

Question 73

Updraft Intensity is (minimized/maximized) within rotating cores.

Answer 73

maximized

Question 74

Precipitation loading in updraft weakness between rotating cores produces a ___________.

Answer 74

downdraft

Question 75

True or False. | A rotating updraft can cause the storms motion to significantly deviate from the Mean Vector Wind (MVW).

Answer 75

True

Question 76

For a cyclonically-rotating updraft, Bernoulli effects produce low pressure on the (right/left) side of the cyclonic updraft in the mid-troposphere, and high pressure on the (right/left) side of the cyclonic updraft.

Answer 76

right | left

Question 77

After splitting, cyclonic storm moves to the (right/left) of the MVW.

Answer 77

right

Question 78

SR supercells are favored within (veering/backing) vertical wind profiles.

Answer 78

veering

Question 79

For an anticyclonically-rotating updraft, Bernoulli effects produce low pressure on the (left/right) side of the anticyclonic updraft in the mid-troposphere, and high pressure on the (left/right) side of the anticyclonic updraft.

Answer 79

left | right

Question 80

Anticyclonic storms moves to the (right/left) of the MVW.

Answer 80

left

Question 81

In a (no-shear/moderate-shear/strong shear) ordinary cell, the gust front rapidly outruns the storm and the storm is left totally entrenched over boundary layer cold pool.

Answer 81

no-shear

Question 82

``` In a (no-shear/moderate-shear/strong shear) multicell, the storm will move downshear at roughly the same speed as the MVW between the surface and 6 km altitude AGL and new cell growth is enhanced along the downshear portion of the gust front. ```

Answer 82

moderate-shear

Question 83

When new cell growth is enhanced along the downshear portion of the gust front in a multicell system, relative flow into the newly-developing cells (increases/decreases) and the length of time cells stay in the vicinity of strong low-level convergence zone and associated lifting near the gust front (increases/decreases).

Answer 83

increases | increases

Question 84

In a (no-shear/moderate-shear/strong-shear) supercell, rotation develops on the flank of the updraft due to vertical tilting of pre-existing horizontal vorticity within the sheared flow.

Answer 84

strong-shear

Question 85

In a strong-shear supercell, if the vertical wind shear extends through the middle-levels of the storm (sfc-6 km AGL), the rotation dynamically induces a (negative(low)/positive(high)) pressure anomaly in the middle troposphere.

Answer 85

negative (low)

Question 86

The (NPA/PPA) produces a strong non-hydrostatic pressure gradient which accelerates boundary-layer air violently upward.

Answer 86

NPA

Question 87

True or False. Rotating updrafts associated with mid-level NPA’s are short-lived and weaken after the storm moves into a more stable environment.

Answer 87

False. | long-lived and remain vigorous after the storm moves...

Question 88

True or False. | Rotation causes storm motion to deviate from the MVW.

Answer 88

True

Question 89

(Unidirectional/curved) shear favors storm splitting as NPA forms at mid-levels within rotating updrafts on both right (cyclonic) and left (anticyclonic) side of original storm.

Answer 89

Unidirectional

Question 90

True or False. | In a unidirectional shear profile, split cells are nearly identical, but rotate in opposite directions.

Answer 90

True

Question 91

In a (unidirectional/curved) shear environment, veering shear vectors winds are climatologically favored.

Answer 91

curved

Question 92

Strongly veering winds favor strongly (right- | moving/left-moving) cells with cyclonic rotation. (Right-moving/Left-moving) anticyclonic cells are not favored.

Answer 92

right-moving | left-moving

Question 93

Match the hodograph descriptions with the appropriate type of storm cell/system. A. Strongly-curved/Weak-shear hodograph B. Strongly-curved/Strong-shear hodograph C. Moderate-curved/Strong-shear hodograph D. Moderate-curved/Deep Strong-shear hodograph E. Moderate-curved/Shallow weak-shear hodograph F. Moderate-curved/Shallow strong-shear hodograph G. Straight/strong shear hodograph 1. Large intense right-flank supercell with hook echo & weak left-moving cell which dissipates. 2. Supercell on south end of multicell line 3. Intense “bow echo” or “derecho” with bookend vortices on left and right flanks. 4. Short-lived multicell 5. Weak multicell squall line. 6. Mirror-image right and left-flank supercells. 7. Right-flank supercell split from weaker left-flank storm.

Answer 93

``` A --> 4 B --> 2 C --> 7 D --> 1 E --> 5 F --> 3 G --> 6 ```