Cloud-to-ground lightning

-Negative: more numerous, comes from cloud base
-Positive: less frequent, from anvil, much stronger, 10-25% of lightning, causes majority of natural forest fires

Cause of dome of cloud to overshoot the anvil strong updrafts and downdrafts
(turbulent)

Storm energy source

Temperature and humidity

Cumulonimbus (Thunderstorms)

-made of large cells forming in 15-30 minutes
-most contain 2 or more cells (multicell storms) Supercell storm

-very large, rotating single cell
-cause tornados, lightning, hail, etc
-most likely to cause hail
-3 types: low precipitation, classical, high precipitation

Cell cycle

cumulus -> mature -> dissipating stages

Energy source for storm (solar energy)

-absorbed at 3 heights: top (thermosphere), middle
(stratopause), bottom (earth surface)- heats ground, which heats air in troposphere (bottom 11km) and powers storms Storm heat

-sensible heat warms air
-latent heat increases humidity

Heating cycle (and time of most thunderstorms) dBZ

-day= solar heating (input)
-night= infrared radiation (IR) cooling
- greatest accumulation of heat at sunset= tstorm formation -Disaster intensity scale for rainfall
-radar eco intensity (in decibals)

Downburst

-cold, dense air sinking
-created at rainfall due to precipitation drag and evaporative cooling
-speeds range from 20-90km/h

Gustfront

-straight line wind due to downburst hitting ground and spreading
-speeds range up to 250km/h

Precipitation and wind cause

-storms draw in humid air causing it to condense and release heat into storm

Saturation value

maximum humidity that air can hold

Adiabatic cooling

-air cools as it rises condensing vapour into liquid and releasing latent heat

Saturation humidity < humidity

Average warming rate

Tornado

= condensation
-causes 3 things: releases sensible heat into storms, reduces humidity down to saturation value, and produces/increases liquid cloud drops

-average temperature change ΔT over time interval Δt
ΔT/Δt= a . RR

-violently rotating column of air stemming from supercells
-made by funnel cloud (water) and/or debris cloud
-some invisible
-most move SW to NE
-shape is independent of intensity classification
-recognize rotation: striations around the mesocyclone, a rotating wall cloud
-tornado translation speed 0-100km/h (slow moving)
-rotational speeds do the damage, much faster
-short lived, narrow, often one to tens of km long

Cloud wall

-isolated lowering of cloud base beneath rising cumulus towers
-outside of precipitation region

Enhanced Fujita Scale

-determined by building damage
EF0 -> EF5

Tornado "outbreak"

Tornado Evolution

-6 tornadoes in one day in one region
-or many in a week
-Early (some rotating dust/debris at ground)
-funnel cloud grows down from tstorm base
-funnel extends to ground and merges with debris cloud to form mature tornado -decrease to "rope" stage
-dissipates (new ones may form nearby)

Mammatus clouds

-can be recognized by Flanking Line at base Positive feedback in storms

-wind blows in warm, humid air

Force creates wind

Newton's second law
F= m . a (mass x acceleration)

Buoyancy force

-vertical
-causes updrift and downdrift

Pressure-Gradient Force (PGF)

- horizontal or vertical
-temperature affecting buoyancy/pressure creating wind
-difference between opposing pressures

Air parcel buoyancy

-depend son the difference between parcel temperature and temperature of surrounding air

Condensation in Tstorms

--releases latent heat which warms air making it rise causing violent updrafts

Hurricane formation

-horizontal changes in temperature
-horizontal changes in pressure that increase with height
-pressure gradient increasing at higher altitudes
-drives faster winds at higher altitudes

Continuity concept

Temperature effects

Hurricane

-air molecules are spread smoothly, evenly, continuous
-air movement is continuous
-initial vertical motion due to buoyancy generates horizontal motion in surrounding air= circulation