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45 Cards in this Set
- Front
- Back
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Most Lightning results from
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within clouds
(cloud-to-cloud lightning) |
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cloud-to-ground lightning
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more dramatic,
occurs less often (20%) -negative charges accumulate in lower portions of the could -positive charges are attracted to a small area in the ground beneath the cloud |
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stepped leader
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shat of negatively charged air
-preceded actual lightning |
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Stroke/return strokes
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When leader approaches ground, and connects with spark surging upward from the ground
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dart leader
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Forms after discharge of first stroke, which neutralizes some but not all of the negatively charged ions at the base of the cloud
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lightning flash
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Combination of strokes from stepped leader and dart leader
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Positive vs. negative strokes
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Positive are more powerful
-positive come from anvil -positive are less frequent |
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ball lightning
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appears as a round, glowing mass of electrified air.
-Seems to roll through the air or along a surface for 15ish seconds before exploding. |
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St. Elmo's fire
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Causes tall objects like church steeples or ship's masts to glow as they emit barrage of sparks. Often produces bluish green tint in the air, and a hissing sound
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Tops of hurricanes and thunderstorms are near
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Tropopause
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Ultimate source of energy driving severe weather
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Solar radiaion
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Most thunderstorms are short-lived because
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Limited availability of boundary-layer fuel nearby
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Mixing ratio
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Mass of water vapour/mass of all remaining gasses
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Mammatus clouds form where?
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bottom of the anvil
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Adiabatic process
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no heat transfer
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Thunderstorms have all updraft in BLANK stage
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Cumulus
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Derecho
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Severe straight-line wind covering area over 400km
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Mesocyclone
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Whole thunderstorms that rotates slowly
-strongest tornadoes are formed |
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Primary force that drives horizontal winds
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Pressure gradient
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Longest lived storm
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hurricane
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"warning" message
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seek shelter from storms/tornadoes/hurricanes immediatley
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Advection
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process which warm humid air moves horizontally toward thunderstorms
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Enhanced Fujita scale classification based mostly on
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amount of damage to structures
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Part of hurricane with strongest winds
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eyewall
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Individual hurricanes last about
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A week
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Haboob
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Dust or sand storm
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Lightning safety (where to take cover)
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1st in a building. Don't stand under tree, or other things can be used as rods. Cars are pretty safe.
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Air mass thunderstorms
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localized, short lived storms that dissipate within ten minutes of formation. -Most lightning comes from these
-Most common -Least destrutive |
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Severe thunderstorms downdrafts will
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Intensify the storms that generate them
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Cumulus stage
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First stage of thunderstorm
-All updraft, -No precipitation -no anvil |
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mature stage
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-Up and downdrafts
-precipitation -start of an anvil -most vigorous stage of thunderstorm |
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dissipating stage
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-Only downdrafts
-weaker precipation -large anvil with diffuse outline |
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severe thunderstorms definition
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Wind speeds more than 93 km/hr
-hailstones larger than 1.9 cm -or spawn tornadoes |
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squall line thunderstorms
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-Heaviest rain cells merge into a long narrow line
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downburst
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-regions of rapidly descending air
-Falling rain drags air down with it -rain falls, cools the air (cold air sinks) |
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Gust front
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Leading edge of cold spreading air
-displaces warm air upward -often can pick up lots of dust and become haboob |
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Supercell
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Single, powerful cell, rather than multiple cells.
-Severe, long lasting, often rotating storms often with hail and tornadoes -last for a long time due to favorable wind shear |
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wind shear
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when wind changes direction or speed with the altitude
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Doppler radar
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Can detect motions inside a storm
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microburst
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small downburst
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Thunderstorm occurence
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-Most common is Florida
-In the tropic areas - |
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Tornado
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Violently rotating columns of air in contact with the ground
-all violent tornadoes come from supercells |
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Tornado speeds
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-Translational about 50 km/hr
-wind speeds from 65 km/hr to above 450 km/hr |
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Wall cloud
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-Isolated lowering of cloud base on SW flank of the storm
-associated with tornadoes |
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Funnel cloud
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Cloud made of water droplets
-like a tornado but yet to touch the ground |
