Thunderstorms

Question 1

Req for Thunderstorm

Answer 1

Instability
Moisture
Lifting Force (Trigger like low p/frontal/surface heating)

Question 2

Squall Line Thunderstorm

Answer 2

100 miles long
Often ahead of cold front

Question 3

Building Stage Of Thunderstorm

Answer 3

• Updraughts
• Deep instability/moisture making cumulus cloud grow
• Wind speeds up to 60kts

Question 4

Mature Phase

Answer 4

Last 20 minutes
Updraughts and downdraughts
Marked by precipitation

Question 5

Dissipating phase

Answer 5

2 hours
Downdraughts only
Energy of downdraughts overcome energy of Updraughts
Lose energy and slow rain
Cloud base lifting due to evaporation

Question 6

Gust Front

Answer 6

20km ahead of storm - 6000ft depth
Usually first indication of TS coming
Cooler air from down draft
Forces warm air to rise condense and develop roll clouds

Question 7

Shelf cloud

Answer 7

Associated with gust front
Humid air rises from cold sinking air

Question 8

Microburst

Answer 8

4km wide and do not last more than 5 minutes
Dry or wet (precipitation)

Question 9

Macroburst

Answer 9

Last longer than 5 minutes and affects a larger area
Usually between 3-5 miles
Entire cold air outflow leaves TS

Question 10

Microburst Hazards

Answer 10

1 - Headwind/airspeed rise
2 - Airspeed drops/high rate of descent
3 - Sudden tailwind/Lower airspeed

Question 11

Virga

Answer 11

Rain that does not reach surface leading to downdraughts from cool sinking

Question 12

Hail

Answer 12

High risk of ice conditions that can damage airframe
GR/GS

Question 13

St Elmo’s fIRE

Answer 13

Visible discharge on windscreen and airframe at night

Question 14

Super Cell Thunderstorm

Answer 14

Upper wind condition allow shifting of CB
No reduction in strength from downdrafts as falls in different area

Self propagating

Question 15

Charge Distribution in Thunderstorm

Answer 15

Positive charged in upper cloud
Negative charge in lower cloud

Question 16

Types of lightning

Answer 16

Intra Cloud
Cloud to Air
Cloud to ground
Cloud to cloud

Question 17

Characters of tornado

Answer 17

Winds speeds can exceed 200kts
Referred to as funnel cloud if not touching ground
Referred to as water spout if over water
Ground speed is 20-40kts
Last up to 30 mins
150 in diameter

Question 18

Dust devil

Answer 18

Rotating air caused by surface heating in hot dry calm conditions

10-100ft wide
Reach up to 650ft

Question 19

Avoidance Info For Thunderstorms

Answer 19

Avoid by 10 miles up to 20,000ft

Avoid by 20 miles all sides and 5000ft vertically when above 20,000ft

Question 20

Airborne Weather Radars Measure?

Answer 20

Detect rain droplets as well as hail/snow
Reflectivity of precipitation depends on diameter and water content of droplets

Blue/Green - Weak
Yellow/Orange - Moderate
Red - Strong

Question 21

Lightning that shows from one cloud to another

Answer 21

Referred to as cloud-cloud

Question 22

How if lightning formed

Answer 22

Result from electrical charge becoming strong enough to jump from cloud to the ground

Question 23

Types of Thunderstorms

Answer 23

Air mass (heat thunderstorms) - no front/local/move slowly

Frontal - fast moving

Squall line thunderstorm - 100 miles long

Orographic thunderstorm

Thermal thunderstorm

Question 24

Wind shear

Answer 24

Variation in wind velocity/direction over short distance

Virga can be a warning sign

Question 25

Thermal Thunderstorm

Answer 25

ELR increases with surface heating As surface heat though day instability builds Likely during warm days with clear skies

Question 26

Air Mass Thunderstorm

Answer 26

Warming of lower levels within air mass when cool air mass moves towards warmer surface Steepens the lapse rate triggering thunderstorms Near coasts in summer

Question 27

Frontal Thunderstorms

Answer 27

Cold air mass undercuts a warm air mass. Develop ahead of a colt front

Question 28

Where is lightning most likely

Answer 28

Within 5000ft of freezing level Temperature between +10 and -10 Strikes a sharp edges like wingtip or nose - becomes part of lightning trajectory

Question 29

Where is hazardous hailstones reaching the ground most likely to be experienced below CBS?

Answer 29

Continental areas of mid latitude due to the freezing level being lower around 11,000ft

Question 30

How many tornadoes typically occur in NA each year

Answer 30

More than 1000

Question 31

Warning sign of wind shear is

Answer 31

Virga