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MET Key Facts > Thunderstorms > Flashcards

Thunderstorms Flashcards

1
Q

Req for Thunderstorm

A

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

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2
Q

Squall Line Thunderstorm

A

100 miles long
Often ahead of cold front

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3
Q

Building Stage Of Thunderstorm

A
  • Updraughts
  • Deep instability/moisture making cumulus cloud grow
  • Wind speeds up to 60kts
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4
Q

Mature Phase

A

Last 20 minutes
Updraughts and downdraughts
Marked by precipitation

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5
Q

Dissipating phase

A

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

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6
Q

Gust Front

A

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

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7
Q

Shelf cloud

A

Associated with gust front
Humid air rises from cold sinking air

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8
Q

Microburst

A

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

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9
Q

Macroburst

A

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

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10
Q

Microburst Hazards

A

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

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11
Q

Virga

A

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

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12
Q

Hail

A

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

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13
Q

St Elmo’s fIRE

A

Visible discharge on windscreen and airframe at night

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14
Q

Super Cell Thunderstorm

A

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

Self propagating

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15
Q

Charge Distribution in Thunderstorm

A

Positive charged in upper cloud
Negative charge in lower cloud

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16
Q

Types of lightning

A

Intra Cloud
Cloud to Air
Cloud to ground
Cloud to cloud

17
Q

Characters of tornado

A

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

18
Q

Dust devil

A

Rotating air caused by surface heating in hot dry calm conditions

10-100ft wide
Reach up to 650ft

19
Q

Avoidance Info For Thunderstorms

A

Avoid by 10 miles up to 20,000ft

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

20
Q

Airborne Weather Radars Measure?

A

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

21
Q

Lightning that shows from one cloud to another

A

Referred to as cloud-cloud

22
Q

How if lightning formed

A

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

23
Q

Types of Thunderstorms

A

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

Frontal - fast moving

Squall line thunderstorm - 100 miles long

Orographic thunderstorm

Thermal thunderstorm

24
Q

Wind shear

A

Variation in wind velocity/direction over short distance

Virga can be a warning sign

25
Q

Thermal Thunderstorm

A

ELR increases with surface heating
As surface heat though day instability builds

Likely during warm days with clear skies

26
Q

Air Mass Thunderstorm

A

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

27
Q

Frontal Thunderstorms

A

Cold air mass undercuts a warm air mass.

Develop ahead of a colt front

28
Q

Where is lightning most likely

A

Within 5000ft of freezing level
Temperature between +10 and -10

Strikes a sharp edges like wingtip or nose - becomes part of lightning trajectory

29
Q

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

A

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

30
Q

How many tornadoes typically occur in NA each year

A

More than 1000

31
Q

Warning sign of wind shear is

A

Virga

MET Key Facts (25 decks)

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