Thunderstorms

Question 1

Describe the Life cycle of a thunderstorm

Answer 1

Cumulus
mature
dissipating

Question 2

The cumulus stage

Answer 2

Moist air rises, cools to its dewpoint
Water vapour condenses as a liquid droplets to form cloud
Heat is released, driving formation of storm cloud

Strong warm updraughts
Droplets are carried higher than the freezing level
Last 10 to 20 minutes

Question 3

The mature stage

Answer 3

Precipitations particles become too heavy and start to fall
Falls cause strong downdraughts
Lightning and first rain from the cloud base occurs

Violent up and downdraughts
Strong horizontal wind shears at the cloud base
Last 20 to 40 minutes

Question 4

The dissipating stage

Answer 4

Water content is at maximum
Updraughts replaced by downdraughts
Disappearance of lightning and hail
Evaporation begins

Question 5

Hazards to aircraft associated with thunderstorms

Answer 5

Wind sheer: causing flight path deviations and handling problems possible structural damage and loss of airspeed

Severe turbulence: causing loss of control and structural damage

Severe icing: possibly clear ice

Interference to radio

Precipitation static

Downburst and microburst

Tornadoes and waterspouts

Hail: damage to the airframe and cockpit windows

Lightning strikes: Can cause electrical are damage and effect instruments

Question 6

Down burst And microburst

Answer 6

strong downdraughts that spread near the ground

Strong down versus not exceeding 4 km is a microburst

Aircraft can be destroyed

Can be spotted by rainfall or dust being blown up

One of the most serious hazards near aerodromes

Question 7

Significant weather avoidance

Answer 7

No definitive visual cues of hail

Black and ugly clouds mean hail is possible

If green hail is highly likely

Question 8

Transiting significant weather

Answer 8

Aircraft expect to operate safely outside 10 NM

Safer to pass up wind of storm where possible

Avoid 20 NM if downwind

Question 9

Techniques to detect significant weather

Answer 9

Active systems you say radar transmitter/receiver
Passive systems detect lightning

Two types:

Weather radar
Storm scarves and strikefinders

Question 10

Detecting thunderstorms and hail

Answer 10

Colour coding to classify weather seriousness

Question 11

Indication of thunderstorms and hail on radar

Answer 11

Squall line
Hooks
Fingers
Scalloped edge
Steep gradient
Attenuation
Horseshoe

Question 12

Squall line

Answer 12

A line of storms that is almost continuous

Difficult to pass

Question 13

Hooks

Answer 13

Cranked form of a single storms cell

Question 14

Fingers

Answer 14

Protrusion from the cell

Question 15

Scalloped edge

Answer 15

Eragon edge to a return

Question 16

Steep gradient

Answer 16

Intensity increases over a short distance

Question 17

Horse shoe

Answer 17

A hollow pattern of cells

Question 18

Attenuation

Answer 18

Severe sells may obscure cells at a greater distance

Question 19

Stormscopes and strike finders

Answer 19

Does not rely on transmitted signal
Passive detection
Can show obscured cells
Relies on electrical discharges