14 Thunder Storms Flashcards
Conditions required for a thunderstorm
- Unstable air
- Humidity
- Trigger
Triggers for a thunder storm
- Orthographic
- Frontal
- Thermal / Convection
- Low Pressure / Convergence
Types of Thunderstorm
- Frontal - warm air is forced up and over a cold front
- Air Mass - Cold air moves in over a warm surface. Air is heated from below via conduction which then rises
- Heat/Thermal - Surface reaches its hottest point in the afternoon so ELR > DALR as air is heated from the surface.
- Squall Line - Line of thunderstorms along a cold front. Multi-cell storm. Most severe conditions.
Name the phases of a Thunderstorm
- Initial / Cumulus / Building
- Mature
- Dissipating
Key facts on Cumulus stage of a thunderstorm
- Up drafts build the cloud up
- Up drafts can reach speeds of 60kts
- Area of low pressure can developers underneath due to up drafts
- Lasts 15 to 20mins
Key facts about the mature stage of a thunderstorm
- Strong up drafts and down drafts
- Latent heat absorbed (Evaporation) - stronger downdrafts
- Rain and Hail
- Updrafts up to 100kts
- Static charge developed by friction between perspiration
- Positive at top, negative at bottom
- Lightning - between -10 and +10 degrees C
- Front gusts 15-20 miles in front - Roll cloud
- Microbursts, area <5km, <5mins
- Macrobursts, area >5km, >5mins
- Lasts 15 to 20 mins
- Max height - 60 to 70K Ft
- 6000ft from surface
Key facts about Dissipating stage of a thunderstorm
- Downdrafts overcome updrafts
- Sinking air evaporates - cloud disperses
- Lasts 1.5 to 2.5 hours
Speed of thunderstorm:
15 - 20kts
- Frontal storms travel the speed of the front
- These are the fastest storms
Where in a storm are tornadoes found?
Trailing edge of a super cell
Diameter of a tornado
100 to 150m
Ground speed of a tornado
20 - 40kts
Wind speeds in a tornado
200kts
How long do tornados last?
Up to 30mins
Where on the globe are tornados mostly found?
Mid-west USA
Late spring to early summer
How are tornados measured?
On the Fujita scale
Hazards associated with a thunderstorm
- Hail - up to 45k ft, structural damage, engine ingestion
- Static electricity - instrument damage, St Elmo’s fire
- Wind sheer - Most dangerous close to ground
- Turbulence
- Icing - Super cool water droplets
- Water ingestion - Engine flame-out, Keep engine igniters one
- Instrument error - Pressure readings, Air speed, Compass
- Virga
Thunderstorm avoidance guidence
- Above 20,000ft, 20 miles
- Below 20,000ft, 10 miles
What signals the start of the mature stage of a thunderstorm?
Start of precipitation
Between the external appearance of a severe thunderstorm and the turbulence and hail that are contained within it, there is:
No Correlation
What sort of cloud will often proceed Thunderstorms?
Castellanus
