Storms Flashcards
Describe types of lightening.
Intra cloud
Cloud to air
Cloud to ground (stepped ladder)
- can be positive (top) or negative (bottom).
Positive are less frequent but stronger, causing wildfires.
Negative are more numerous, come from cloud base
Need 3B volts/km to spark
90% of people survive lightning strikes!!
Lightning can hit a tree too (shrapnel)
Explain sequence of events in a lightning strike
Lightning can get to you directly or indirectly (through a tree!)
Charge comes from above and below, when the meet there is a flash of electricity.
This can hit trees, the ground, can “side step” onto you from a tree.
Explain lightning risk, dangerous times/places/how it effects people and how you can stay safe
Africa has highest density, Florida has highest in N.America
Lightning causes 6-12 deaths/year, 2.4M groundstrikes, worst in alberta.
Weather satelites have optical transient detectors to observe lightning.
Count seconds after flash (sound travels slower) and divide by 3 to get km!
Use the 30/30 rule, count, 30 seconds or less get inside for at least 30 minutes after last lightning/thunder!!
Safe places: in cars with windows up, permenant buildings
Unsafe: small structures, huts, metallic poles, trees, water, open fields, hill tops.
Do “lightning safety crouch”
Identify typical components of a thunderstorm cloud.
Thick clouds with lightning and thunder
Top of cloud: troposphere (10-15km)
Cloud base (1 km)
Looks like anvil or mushroom.
Strong updrafts and downdrafts (turbulent)
If updrafts are strong enough, they overshoot cloud.
100s of km in diameter. Main updraft can be 15km diameter.
Gets energy from temp and humidity.
Cumulonimbus (CB) has many parts. Mad up of large cells that evolve in 15-30 mins.
Multicells (2+ storms in different stages)
Squall line: line of thunderstorms
Supercell: cause tornades, low precip, classic and high precip.
Life cycle: Cumulus (no rain, just updraft, no anvil) Mature stage (both drafts, rain, crisp anvil) Dissipating stage (fuzzy anvil)
Describe nature and evolution of cells in different thunderstorms
Identify atmospheric layers and explain their relationship to storms
Sun is source of atmospheric heat. Absorbed at 1. Thermosphere 2. Statopause 3. Earth's surface (bottom)
Radiation is absorbed at top of atmosphere where its thin to make it warm. Until stratopause where UV is absorbed by oxygen to make ozone. Prevents dangerous UV from entering. Only visible light is left which goes down to the surface.
Most storms occur in the troposphere!
Explain how solar energy can get into the atmosphere to power storms.
Solar energy can be reflected from ground and clouds.
It can be absorbed, making ground warmer. Warm group warms the air as sensible heat, temp increases, and latent heat (humidity increases, evaporates water)
Temp and humidity power storms.
Earth has net input of solar heating during day and infared radiation (cooling) during the night AND day. Greatest accumulation of heat at sunset. Reach “thunderstorm threshold”
List and describe storm hazards and disaster scales covered in this course.
Observing and monitering using remote sensors: radar (anytime) and satellite (daytime).
dBZ scale: intensity of rainfall. DBZ= radar echo intensity (in decibals). if you know dbz you can estimate amount of rainfall. Helps warn potential storm victims.
Name and describe characteristics and hazards of squall lines and 3 of the main types of supercell thunderstorms
Squall line: Consist of many thundarstorms, in a linear or quasi linear - forms a cold front that heads SE and the line moves NE (usually)
Supercell:
-low precip: high hail
- classical: rainy, well defined updraft, rotating
- high precip: high rain, not very visible
MANY ARE HYBRIDS
-mesocyclone: spinning supercells
Use weather radar and satellite to identify and predict storm charictaristics
OKAY!
Identify downbursts and gust fronts, describe how they form and look and what their hazards are.
Downbursts: cause flash floods. speeds of 20-90 km/hour. Cold (dense) air sinking, tstorm creates dense air where rain falls, due to evaporative cooling.
Invisible, dangerous to aircraft
Gust Front: leading edge of horizontal winds (250km/hour!)
When downburst ‘spreads out’
Visible when there is haboob (dry) or arc cloud (moist air)
Can blow down stuff
Virga: when rain evaporates before it hits the ground, causing downburst.
Explain how humidity saturation, latent heat, advection and adiabatic cooling effect storm energy.
Storm Energy
1. Humidity, amount of water vapour in the air. Mixing ratio: water vapour in air/all other vapours. Usually around 0.011
2. Saturation: equilibrium between evaporation and condensation. Maximum humidity that air can hold, varies exponentially with temp (warm air holds more water)
3. Adiabatic cooling: when air rises it looses 10C/km. which holds less water, so it must condense into liquid droplets, condensation releases latent heat.
4. Latent heat turns into sensible heat to make things warmer during CONDENSATION. When saturation humidity becomes smaller than actual humidity.
Reduces humidity to saturation value and can increase liquid cloud drops which turn into raindrops
Describe tornado shapes, what makes them visible and where they form relative to thunderstorm
Supercell tornado (most violent) Gustnados/dust devils Landspouts (soda straw) Waterspouts Cold air funnels
Made visible by cloud water droplets. Funnel cloud (dust or debris from ground) and DEBRIS cloud. Some tornados are invisible. Tornados are attached to thunderstorms, only 30% of tstorms produce tornados. Move from SW to NE - best viewing is on SE of the storm. Tornados attached to updraft of storm
Can often see striations around mesocyclone, and a rotating wall cloud.
Discuss disaster scales and speeds. Use photographs and videos to identify tornado intensity on EF scale
Horizontal movement (Translational)
- slower, SW to NE, speeds from 0-100km, can drive away from them.
Rotational movement (tangential)
- faster than translational speeds, cause DAMAGE.
Classified 2 ways
North america: ENHANCED FUJITA SCALE (EF 0-5) Determined by damage
Europe: TORRO scale. Determined by wind speed
Describe tornado evolution, tornado outbreaks, and mesocyclones.
Outbreaks: 6 tornados in one day or multiple throughout the week in one region.
Occur every year in NA.
Squall line is a line of thunderstorms, tornado outbreaks are associated with these. Create parallel lines of damage.
Tornado evolution:
- Dust whirl, Tstorm
- Funnel cloud
- Mature tornado
- Decaying rope
- Dissipating (but new storm could be right behind you!
Explain tornado hazards and safety procedues and times/locations of greatest risk
Usually short lived, damage path up to size of house or city block.
Safest place to be: indoors is below ground, get OUT OF MOBILE HOMES
get into a ditch or hole below “line of fire”
Drive away from path, perpenticular
Risk: southeastern states, middle provinces.
Low risk in canada
Reflectivity is less good a method, relies on hook echo. Now DBZ (doppler velocity) shows us velocity of raindrops carried by winds. much better.
