Thunderstorms

Question 1

What are the conditions needed for thunderstorms

Answer 1

A trigger action
High humidity or moisture through a deep layer
Instability through a deep layer (ELR>SALR)

Question 2

Where are TS likely to be

Answer 2

In areas of strong convection and frontal activity

Question 3

What are the types of TS

Answer 3

Air mass - Heat and Orographic
Frontal

Question 4

Properties of an Air Mass heat TS

Answer 4

Over land = insolation
Over sea = advection
Mostly mid afternoon and in summer months
From weak pressure systems - cyclonic action

Question 5

Properties of Airmass orographic TS

Answer 5

Moist and unstable air has to rise over mountains
Any time even in winter
Then remains stationary or floats downwind

Question 6

Properties of frontal TS

Answer 6

Trigger action = frontal uplift
Creates a squall advancing line of TS (100nm extend)
More freq in winter
Moves in direction of wind

Question 7

What are the stages of a TS

Answer 7

Developing
Maturing
Dissipating

Question 8

What occurs in the developing stage

Answer 8

Up draughts throughout the cell
Process is 15-20mins
Small diameter

Question 9

What occurs in the maturing stage

Answer 9

Both up and down currents
All severe weather to be expected
Marked by onset of precipitation

Question 10

What occurs in the dissipating stage

Answer 10

Downdraughts
Spreads out into an anvil
Takes 1-2 hrs

Question 11

Time difference between a single and multicell TS

Answer 11

Single - 1-2hrs
Multi - 3-4hrs+

Question 12

What is a roll cloud

Answer 12

A line of turbulent cloud at the leading edge of a TS
Or along a squall line

Question 13

What is a squall line

Answer 13

A line of TS

Question 14

What a squall line represent

Answer 14

Cold front indicator as form ahead of the
Form in areas of rising humid air

Question 15

What is a multi cell TS

Answer 15

As one cell is dissipating another is forming within and it creates a strong gust front at the base of the Cb

Question 16

What is a key feature of a supercell TS

Answer 16

A mesocyclone phase which is a spinning column of air that pulls up draughts even higher

Question 17

Thunderstorm hazards inc

Answer 17

Turbulence, downdraft, windcheater
Lightning
Intrument errors
Static electricity
Tornadoes
Icing
Rain - micro and macro bursts
Hail

Question 18

Different categories of reporting turbulence

Answer 18

Light chop
Light turb
Mod chop
Mod turb
Severe
Extreme

Question 19

What can detect TS in the aircraft

Answer 19

Airborne weather radar
Stormscope

Question 20

How much should you avoid Cbs by

Answer 20

10nm and 5000m
Or
625ft and 2.5km

Question 21

Attenuation is

Answer 21

When the return signal from a cloud is so strong the radar can’t show anything behind the cloud
Eg. Creating a shadow

Question 22

Properties of a microburst

Answer 22

5mins long and less than 5km diameter

Question 23

Where can hail be expected in a Cb

Answer 23

Between the ground and Fl450

Question 24

Do airmass heat TS have diurnal var

Answer 24

Yes a marked diurnal variation

Question 25

What are destructive tornadoes associated with

Answer 25

Mesocyclones