Thunderstorms

Question 1

What are the development stages of a thunderstorm?

Answer 1

Cumulus, Mature and Dissipating.

Question 2

Explain Updraft phase of the Cumulus stage.

Answer 2

Updraft: Small convective clouds merge and grow into a convective cell. Only updrafts are present and they draw air into the base/ sides of cloud.
Base of cumulus: Up to 4000 ft.
Height: Over 20 000ft.
Updraft Speed: 3000 ft/min

Question 3

Explain Updraft phase of mature stage.

Answer 3

Rain at earth’s surface indicates the mature stage.
Cloud continues to grow, updrafts reach max speed of 6000 ft/min.
Cloud reaches tropopause, possibly stratosphere if updraft strong enough. As a result, an anvil shape of cloud may form.

Question 4

Explain the Down/ Microburst phase of the Mature Stage.

Answer 4

Exceptionally violent winds that last for a few minutes, only about a mile across.
Originate out of downdrafts that flow out and away from storm.

Question 5

Which thunderstorms do hail exist in?

Answer 5

All thunderstorms.

Question 6

Where does hail develop and exist?

Answer 6

Develops and exists between 10 000 and 30 000ft.

Question 7

What is the distance hail can be thrown?

Answer 7

Up to five miles ahead of storm, originating in the clear air under the anvil.

Question 8

What causes a roll cloud?

Answer 8

The cool outflow that slides under the warm inflow.

Question 9

What must occur side by side for lightning to occur?

Answer 9

Strong up and down drafts.

Question 10

What must move up and down in the drafts for lightning to form?

Answer 10

Water droplets, hail and snow.

Question 11

What’s the differences/ similarities between a funnel cloud and a tornado?

Answer 11

Tornado contacts ground, funnel cloud hangs down from cloud.

Both are violent rotating columns of air descending from a thunderstorm.

Question 12

In which quadrant of a TS does a tornado exist?

1) SW
2) NE
3) NW
4) SE

Answer 12

SW

Question 13

State position (ahead, below or behind) of the Gust front, a microburst and a tornado.

Answer 13

Gust front: Ahead of storm

Microburst: Below or just ahead of storm

Tornado: Behind storm

Question 14

What happens towards the end of the Mature stage with regards to up/ down drafts?

Answer 14

Up draft weakens until entire cell comprises of downdrafts.

Question 15

What are the types of frontal thunderstorms?

Answer 15

Warm frontal, cold frontal, trowal and squall line.

Question 16

Which type of frontal TS is least and which is most severe?

Answer 16

Warm front: Least severe

Squall Line: Most severe (may contain hail, destructive winds and tornadoes.)

Question 17

Which type of frontal TS moves away from front?

Answer 17

Squall line

Question 18

Formation in a warm, moist air mass, in no way associated with a front and typically isolated or widely scattered indicates which type of thunderstorms?

Answer 18

Air mass thunderstorms.

Question 18

Formation in a warm, moist air mass, in no way associated with a front and typically isolated or widely scattered indicates which type of thunderstorms?

Answer 18

Air mass thunderstorms.

Question 19

What are the types of Air Mass TS?

Answer 19

Convective, Orographic and Nocturnal.

Question 20

What is the most common hazard associated with TS?

Answer 20

Turbulence

Question 21

If a TS has more lightning, does it have more or less turbulence?

Answer 21

More turbulence

Question 22

Radar weather avoidance of a TS requires what distance for:

a) Flying below the freezing level
b) Flying above the freezing level
c) Flying above 30 000 ft.

Answer 22

a) 5 miles
b) 10 miles
c) 20 miles.

Question 23

As a general rule, how high should you clear the top of a TS for every 10 kts of wind speed at cloud top level?

a) 500 ft
b) 1000 ft
c) 2500 ft
d) 3000 ft

Answer 23

1000 ft

Question 24

During approach and landing heavy rain can cause loss of lift due to roughening if the upper wing surface. What else can it do?

Answer 24

Reduce visibility and cause hydroplaning during landing.

Question 25

Not all water in a TS falls to earth, can suspended raindrops be dangerous to the aircraft?

Answer 25

Yes, they can do as much damage as hail.

Question 26

The heaviest icing conditions in a TS are found where? And why?

Answer 26

Just above freezing level due to largest concentration of super-cooled water droplets.

Question 27

What does a Gust Front result in regarding wind, temp and pressure?

Answer 27

Change in wind speed/ direction, sharp cooling and pressure rise.

Question 28

Where is the gust front strongest? How far can it extend beyond a TS?

Answer 28

Ahead of TS and 10 - 15 miles ahead.

Question 29

What is a gust front indicator?

Answer 29

Shelf clouds that form near leading edge.

Question 30

The possibility of a lightning strike on aircraft ______ with ______ aircraft size.

[increase(s)(d) or decrease(s)(d)]

Answer 30

Increases and increased

Question 31

What are the two types of lightning?

Answer 31

Triggered and Natural.

Question 32

Which type of lightning is associated with static charge?

Answer 32

Triggered

Question 33

Which type of lightning is associated with strong radar returns?

Answer 33

Natural lightning

Question 34

Explain the pressure variations as a TS approaches, moves overhead and moves on.

Answer 34

Abrupt fall on approach
Abrupt rise when overhead
Gradual return as it moves on