Chapter 14: Thunderstorms (PP ch 13)

Question 1

TS Requirements

Answer 1

Instability, Humidity, Trigger

Question 2

TS Triggers (4)

Answer 2

Surface Heating
Airmass
Frontal
Orographic

Question 3

Cb TS Formation

Answer 3

Building (20 min) Cu Humerous. 60 kn updraft
Mature (20 min) TCu 100kn updraft, downdraft evaporation so T reduces
Dissipation 1.5 - 2.5 h, cold downdraft only

Question 4

Supercell Storm

Answer 4

TS + high windshear tilts TS
column of updraft (vortex), column of downdraft
self propagating
Shelf clouds
Roll clouds

Question 5

Squall Lines

Answer 5

Line of TS preceding cold front

hundred miles long

Question 6

Mesoscale Convective Area

Answer 6

Squalls dissipate in individual cells i.e. multi-cell TS (West coast Africa over ocean)

Question 7

TEM of TS (5)

Answer 7

Shooting Hail
Microburst
St Elmo's fire (blue plasma)
Lightning (heating + SS shockwave)
Instrument Deviation (Pressure, magnetism)

Question 8

Microburst Characteristics (4)
Flying through (3)

Answer 8

Cold, dense air
4km diameter, < 5 min, Vz = 170 kn
1. Headwind
2. Downdraught (loss altitude)
3. Tailwind

Question 9

Cloud Electrical Charge Distribution

Types of LS (4)

Answer 9

- bottom Cb, + top Cb, + ground
CC cloud to cloud
CG cloud to ground
IC Intra-cloud
CA cloud to air

Question 10

Tornadoes

Wind speed, diameter, scale, where?

Answer 10

100 - 200 kn
100 - 150 m diameter
Fujita scale
Mid west USA late spring - early summer

Question 11

Weather Radar

TS clearance in-flight

Answer 11

Reflects precipitation
> FL200 - avoid by 20 mi, 5000’
< FL200 - avoid by 10 mi, 5000’

Question 12

TRS Stages (4)

Answer 12

1. Tropical disturbance < 20 kn
2. Tropical depression 20 - 33 kn. Depression on chart
3. Tropical storm 34 - 63. Convective clouds
4. Tropical revolving storm > 64 kn

Question 13

TRS

Requirement, Diameters, Height, Pressure

Answer 13

Formed over water ( > 26.5C)
500 - 2000 km diameter
Eye 20 - 50 km diameter
12 km high
Low pressure

Question 14

TRS Formation Location, Travel Direction and Names

Answer 14

5 - 20 deg from equator (No Coriolis at equator)
Travels west
Northen H. goes up, Souther H. goes down
Typhoons: South-East Asia
Hurricanes: East + West N. America
Cyclones: Australia, India, Madagascar (no S. America)

Question 15

TRS Location (%), # Tropical Storm, # TRS
Difference between TS and TRS

Answer 15

Location - % - # Tropical S ( > 33kn) - # TRS ( > 64 kn)
Typhoons - 32% - 26 - 17
E. Australia - 10% - 10 - 5 
W. Australia - 6% - 8 - 5
India - 6% - 4 - 2
E. Africa - 8% - 10 - 5
E. America - 12% - 12 - 6
W. America - 16% - 16 - 8

Question 16

Easterly Waves

Synonims (2), Relationship to RTS, Direction

Answer 16

Tropical Waves, African Easterly
1 / 5 become RTS as warm dry air goes over water
Western Africa to Caribbean
Most convective activity at trailing edge of backside