Progress Test 11

Question 1

What conditions are required for a thunderstorm to occur?

Answer 1

-An unstable atmosphere
-A supply of moist air
-A lifting triggering action

Question 2

At what point does an air mass become unstable?

Answer 2

Between the DALR and the SALR, The in which there is little temperature difference and the air mass turns to a SALR.

Question 3

What effect does more moisture have on a thunderstorm?

Answer 3

The more moisture in the air the larger the thunderstorm will be.

Question 4

Name four lifting triggering action that can cause a thunderstorm.

Answer 4

1. Convection
2. Frontal Lift
3. Orographic Lifting
4. Convergence

Question 5

Convection occurs due to hot spots that cause local lifting , most UK thunderstorm are caused this way. Where do these hotspots occur?

Answer 5

Large areas of surface heated by the sun.
E.g. cities and industrial areas.

Question 6

True or False. Frontal lift only occurs at warm fronts.

Answer 6

False. Frontal Lifts occur at both warm and cold fronts. However, warm or occluded fronts are more dangerous since TCU/CB/TS can be embedded in the associated layer cloud.

Question 7

What is Orographic Lifting?

Answer 7

Caused by terrain which force the air upwards.

Question 8

Convergence is when two differing air masses meet, where is this more likely to occur?

Answer 8

At coastal locations with sea/land breezes

Question 9

True or False? A single thunderstorm may have several cells (each having it’s own life-cycle).

Answer 9

True

Question 10

During a thunderstorm the Cumulus stage is when there is a large vertical growth (TCU), when is CU a TCU?

Answer 10

When the cloud is taller than it is wide.

Question 11

The Cumulus stage there are huge vertical air currents inside the cell which can have a rate of climb of over 4000ft, What does this cloud look like?

Answer 11

The cloud is bright white with hard edges.

Question 12

The mature stage ofa thunderstorm can last for about 1 hour with heavy precipitation (+RA, +SN, +GR), True or False? Massive vertical air currents only occur in the walls of the cloud and lighting and thunder are not present in this stage.

Answer 12

False. Massive vertical air currents not only inside but also in the vicinity of the cell, Lightning and thunder are present in this stage due to air current friction.

Question 13

Towards the end of the maturing stage what is formed and what is it made of?

Answer 13

An anvil like form in the direction of the winds aloft. Made of ice crystals at the top of the troposphere (the cloud then has stopped the vertical ascent)

Question 14

In the mature stage extremely strong down draughts can occur as the cell has a gust front, how fast are these down draughts and where do the occur?

Answer 14

Can be up to speeds of 40kts and felt up to 20nm away from the cell.

Question 15

What are roll clouds?

Answer 15

Roll clouds are formed at the gust front and indicate turbulence.

Question 16

During the dissipating stage the falling precipitation dampens up the draughts and the cell begins to loose energy, what does the cloud form?

Answer 16

The cell forms a flat top due to an inversion which makes an anvil like shape more prominent.

Question 17

What is a supercell?

Answer 17

Occurs when the winds aloft within the cell move the precipitation away from up draughts.

Question 18

A supercell produces a long living cell at the mature stage, what also occurs?

Answer 18

Increased vertical acceleration
Self sustaining supply of moist air is present.

Question 19

Name 6 hazards of thunderstorms.

Answer 19

1. Turbulence
2. Precipitation
3. Lightning
4. hazards to the pilot
   5.Icing
5. Direction of the front

Question 20

Turbulence can occur both inside and outside a cell which can lead to up draughts and down draughts, what effect does this have on the aicraft?

Answer 20

This causes the ROC to increase and decrease rapidly, can reside next to each other. Can lead to extreme stresses on the airframe (+- 4000ft/min)

Question 21

Turbulence can cause wind shear from the sudden up and down draughts, where is wind shear found?

Answer 21

A downdraught exists beneath the cloud and spreads up along the ground. Causes severe wind shear hazard below and at the gust front of the cell.

Question 22

What are mammatus clouds?

Answer 22

Clouds shaped like an irregular egg box and indicate turbulence. Should not fly beneath.

Question 23

Precipitation is a hazard of thunderstorms, what type can occur?

Answer 23

-Heavy rain which can go into the engines via the intake and become flooded due to the intensity of water present.
-Heavy snow can be present which effects the visibility and can freeze the airframe and windshields.
-heavy Hail (GR) the size of stones can damage the airframe. Hail stone are larger the higher they are.

Question 24

Another hazard of thunderstorms is Lightning, what type of aircraft is a good conductor?

Answer 24

Metal aircraft are good conductors of electricity and does not generally effect the structural integrity of an aircraft.

Question 25

True or False. Glass enforced plastic and wood and fabric aircraft are not good conductors.

Answer 25

True.

Question 26

What effect does lightning have on aircraft equipment?

Answer 26

The ADF will give unreadable readings in the vicinity due to the broad radio frequencies of lightning. Other equipment like the compass, comms, onboard computer based systems and navigation equipment may be damaged.

Question 27

For one nautical mile away of thunderstorms, how much time between thunder claps will there be?

Answer 27

5 seconds.

Question 28

What the effect of thunderstorms on the pilot?

Answer 28

Pilots are generally safe but can be temporally blinded by the flash for seconds or minutes and can be temporally deafened by the thunder clap.

Question 29

What causes thunder to sound?

Answer 29

It is caused by the sudden massive expansion of the air around the lightning bolt due to it's sudden increase in temperature.

Question 30

How can icing be a hazard during thunderstorms?

Answer 30

Icing within a thunderstorm is classes as severe and even ani-icing systems cannot tolerate ice build up.

Question 31

Thunderstorm may be severe if the dew point is greater than 20 degrees, pilots should remain clear of cloud of fly above the haze layer for better visibility. Connective thunderstorms are widely spread, what about squall lines?

Answer 31

Squall lines may be impossible to avoid so diversion should take place.

Question 32

True or False? Small thunderstorms are 5nm wide and large can be 30nm wide.

Answer 32

True.

Question 33

Should you fly over TS's?

Answer 33

No.

Question 34

How far ahead can weather associated with the front be?

Answer 34

20nm.

Question 35

True or False? TS's are not hazards if the aircraft is on the ground.

Answer 35

False.

Question 36

What is the symbol for thunderstorms on a chart?

Answer 36

hangman with a lightning bolt.

Question 37

What type of aircraft does lightning pose a threat to?

Answer 37

All.