Thunderstorms and Hazards

Question 1

What type of cloud forms thunderstorms?

Answer 1

Cumulonimbus

Question 2

What defines a thunderstorm?

Answer 2

Cumulonimbus with thunder and lightning.

Question 3

What are the three conditions required for thunderstorms to form?

Answer 3

1. High Humidity (abundant moisture)
2. Instability
3. Trigger Action (A lifting mechanism)

Question 4

What can the diameter of the thunderstorm cell reach?

Answer 4

10 km

Question 5

How long is the lifecycle of a typical thunderstorm cell?

Answer 5

60 minutes

Question 6

What are the three stages in a thunderstorms lifecycle?

Answer 6

1. Cumulus
2. Mature
3. Dissipating

Question 7

What is the cumulus stage characterized by? How long does this stage last?

Answer 7

• Strong updrafts throughout the cloud.
• Rapid vertical growth
• 15 minutes

Question 8

What is the mature stage characterized by? How long does this stage last for?

Answer 8

1. Strong downdrafts of cold air below the cloud and up draughts through the cloud
2. Precipitation
3. Wind shear
4. Turbulence
5. Gust front spreading out along the surface below the cell.
6. Anvil shape is created
   - lasts for 15-30 minutes

Question 9

What is the dissipating stage characterized by? How long does this stage last for?

Answer 9

• Lasts for approximately 30 minutes

- Only downdraughts in this stage

Question 10

What are the two main formation mechanism of thunderstorms?

Answer 10

1. Frontal

2. Air Mass/Orographic

Question 11

What are some significant hazards to aircraft associated with thunderstorms?

Answer 11

1. Lightning
2. Adverse Wind
3. Downburst
4. Microburst
5. Turbulence
6. Icing
7. Hail
8. Rapid altimeter changes
   9 Static electricity discharge
9. Tornadoes

Question 12

What is lightning?

Answer 12

Static electrical discharge that occurs across very large electric potentials (voltages) that form:

• Within a single cumulonimbus
• Between clouds (or an aircraft)
• Between the cloud and the ground

Question 13

Which stage of the thunderstorm does lightning most typically occur?

Answer 13

Mature stage

Question 14

What are some effects of a lightning strike on an A/C?

Answer 14

• Damage to radios, flight control computers, airframe magnetism
• Flash which may cause temporary blindness

Question 15

What is a downburst?

Answer 15

Strong downward current of air below a thunderstorm cell.

Question 16

What is a microburst?

Answer 16

Really strong downburst

Question 17

What are some methods to detect and avoid windshear?

Answer 17

1. Doppler radar
2. A/C systems for wind shear detection and avoidance
3. Pilot techniques

Question 18

What distance can strong turbulence exist within, above and up to around the thunderstorm?

Answer 18

20 NM

Question 19

Can A/C weather radar systems detect hail?

Answer 19

No

Question 20

What do static wicks do?

Answer 20

Control the discharge of static electricity into the atmosphere.

Question 21

What cloud do tornadoes normally come from and what causes them?

Answer 21

• Cumulonimbus thunderstorm cloud with anvil shape.
• Formed when a disruption to the upper wind flow through the top of a cumulonimbus cloud causes the air aloft with potential vorticity to be transported through the cloud to near the surface.

Question 22

What are water spouts?

Answer 22

• Related to tornadoes but are observed over the sea
• Form with towering cumulus clouds of cumulonimbus cloud
• Not necessarily associated with thunderstorms.

Question 23

When do dust devils/willy willies form?

Answer 23

In dry air that is lifted up and rotates at high speeds.

Question 24

Should you ever fly through a thunderstorm?

Answer 24

No!