Thunderstorms and Hazards Flashcards
What type of cloud forms thunderstorms?
Cumulonimbus
What defines a thunderstorm?
Cumulonimbus with thunder and lightning.
What are the three conditions required for thunderstorms to form?
- High Humidity (abundant moisture)
- Instability
- Trigger Action (A lifting mechanism)
What can the diameter of the thunderstorm cell reach?
10 km
How long is the lifecycle of a typical thunderstorm cell?
60 minutes
What are the three stages in a thunderstorms lifecycle?
- Cumulus
- Mature
- Dissipating
What is the cumulus stage characterized by? How long does this stage last?
- Strong updrafts throughout the cloud.
- Rapid vertical growth
- 15 minutes
What is the mature stage characterized by? How long does this stage last for?
- Strong downdrafts of cold air below the cloud and up draughts through the cloud
- Precipitation
- Wind shear
- Turbulence
- Gust front spreading out along the surface below the cell.
- Anvil shape is created
- lasts for 15-30 minutes
What is the dissipating stage characterized by? How long does this stage last for?
- Lasts for approximately 30 minutes
- Only downdraughts in this stage
What are the two main formation mechanism of thunderstorms?
- Frontal
2. Air Mass/Orographic
What are some significant hazards to aircraft associated with thunderstorms?
- Lightning
- Adverse Wind
- Downburst
- Microburst
- Turbulence
- Icing
- Hail
- Rapid altimeter changes
9 Static electricity discharge - Tornadoes
What is lightning?
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
Which stage of the thunderstorm does lightning most typically occur?
Mature stage
What are some effects of a lightning strike on an A/C?
- Damage to radios, flight control computers, airframe magnetism
- Flash which may cause temporary blindness
What is a downburst?
Strong downward current of air below a thunderstorm cell.
What is a microburst?
Really strong downburst
What are some methods to detect and avoid windshear?
- Doppler radar
- A/C systems for wind shear detection and avoidance
- Pilot techniques
What distance can strong turbulence exist within, above and up to around the thunderstorm?
20 NM
Can A/C weather radar systems detect hail?
No
What do static wicks do?
Control the discharge of static electricity into the atmosphere.
What cloud do tornadoes normally come from and what causes them?
- 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.
What are water spouts?
- Related to tornadoes but are observed over the sea
- Form with towering cumulus clouds of cumulonimbus cloud
- Not necessarily associated with thunderstorms.
When do dust devils/willy willies form?
In dry air that is lifted up and rotates at high speeds.
Should you ever fly through a thunderstorm?
No!
