Lesson 11 Flashcards
What are the 3 requirements for thunderstorm formation
All thunderstorms require:
* Unstable air
* Lifting action to get air moving upward
* High moisture content in the air
What are the 2 types of thunderstorms:
- Air mass thunderstorms
- Frontal thunderstorms
There are ten areas of concern when flying in or near a thunderstorm. Name a few (5)
Turbulence, Hail, Lightning, Icing, Squall lines, Tornadoes, Low ceiling and visibility, Heavy rain showers, Microbursts, Gust fronts
How does icing form on an aircraft?
When an aircraft flies at or below freezing temperatures and strikes supercooled water droplets,
the droplets freeze and adhere to the aircraft. The result is icing.
What are the 3 stages in the formation of thunderstorms?
Cumulus stage
Mature Stage
Dissipating stage
A thunderstorm is a weather phenomenon produced by what cloud?
What accompanies a thunderstorm?
A thunderstorm is a weather phenomenon produced by a cumulonimbus cloud (CB).
Thunderstorms are always accompanied by thunder and lightning and are usually accompanied
by strong gusts of wind and heavy rain.
Severe thunderstorms can be extremely dangerous and may also produce hail and tornadoes.
Describe the cumulus stage
Formation of a cumulus cloud that gradually becomes a towering cumulus
Mostly updrafts and no precipitation
Describe the mature stage
Onset of precipitation/highest incidence of precips
Lightning, microbursts, gust fronts, hail, and tornadoes can also occur at this stage.
Updrafts 6000 feet per minute (FPM). downdrafts in the 2000 FPM
Violent turbulence is associated with these updrafts and downdrafts and also icing.
Describe the dissipating stage
The onset of precipitation during the mature stage causes thunderstorms to dissipate
The top of the cloud spreads out into an anvil form.
Describe air mass thunderstorms
Air mass thunderstorms form when warm, moist, and unstable conditions exist in the
atmosphere.
Air mass thunderstorms usually form as the result of convection, advection, or orographic lift
Describe convection thunderstorms
Convection thunderstorms are caused by the uneven heating of the ground.
Afternoon or early evening and dissipate late
in the evening or overnight.
Slouds are scattered over a large area.
Describe Advection Thunderstorms
Cold air passing over a warm surface
Over warm land/Afternoon/Scattered/Northerly flow
Over warm water/morning/close together/southerly flow
Describe orographic thunderstorms
Lifted up a slope/Dissipate if wind changes direction/Stationary line
Describe frontal thunderstorms
Frontal thunderstorms are caused by humid or unstable air being lifted by the frontal surface. Form in a solid line.
Describe cold front thunderstorms
Clouds are in a line parallel to the front.
They dissipate with the movement of the front
Describe warm front thunderstorms
embedded in stratiform clouds
not as visible as cold front thunderstorms.
they dissipate with the movement of the front.
Discuss turbulence and thunderstorms
The strongest turbulence in a cloud occurs during the mature stage generally between 12 000 and 20 000 feet
(zone of updrafts and downdrafts)
- Below the cloud, downdrafts that race towards the ground cause low-level wind shear
Above the cloud, turbulence is also possible and
outward up to 30 km
Severe turbulence is present in all cumulonimbus clouds.
Discuss Hail and thunderstorms
Hail occurs in the mature stage of thunderstorm cells that have more intense updrafts.
from the surface up to around 10 000 to 15 000 feet
Hail can cause damage to aircraft windshields, outside instrument sensors, and even airframes.
What is lightning?
Lightning is the visible electric discharge produced by a thunderstorm. Lightning is always present in, or in the vicinity of, CBs
What are the 4 types of lightning
- In-cloud (also called sheet lightning)
- Cloud-to-cloud
- Cloud-to-ground
- Distant
Electricity generated by thunderstorms can cause serious problems for aircraft: List them.
- Punctures to the skin of the aircraft
- Damage to communication and navigational equipment
- Temporary blindness of pilots
- Errors in magnetic compasses
- Disruption to low and medium radio frequencies
- Ignition of fuel vapours (rare)
What is a squall line
Squall lines are non-frontal, narrow bands of highly active thunderstorms. They generally
develop ahead of a cold front in moist and unstable air
What is a gust front
Result of strong downdrafts in the mature stage of a TS reaching the ground and spreading out horizontally
Effects of cloud types on flight. CU
Flying near a CU cloud will result in a bumpy flight beneath and in the cloud.
Effects of cloud types on flight. TCU
Flying near a TCU cloud will result in turbulence.
Icing is possible in TCU at altitudes above the freezing level
Effects of cloud types on flight. CB
Flying near a CB cloud will result in severe turbulence.
There may also be severe icing.
Effects of cloud types on flight. ACC
Flying near an ACC cloud will result in turbulence and icing. Precipitation may also be present with ACCs.
What are the hazards associated with CBs. Effects of CBs on aircraft.
Hazards associated with CBs include:
* Rapid changes in barometric pressure
* Abrupt changes in wind speed and direction
* Moderate to severe icing
* Hazardous precipitation
* Electrical disturbances
* Turbulence
* Extreme weather
