Chapter 13.1
Thunderstorms



Abundant source of
moisture and latent
heat that maintains
warmth and upward
motion
The air must lift and
condense, releasing
the latent heat
The atmosphere
must become
unstable
Thunderstorm Frequency
Air-mass Thunderstorms
Caused by unequal heating of the Earth’s
surface
 Most common in the afternoons

Frontal Thunderstorms
Caused by converging warm and cold
air masses
 More frequent during an advancing cold
front

Stages of a Thunderstorm
Chapter 13.2
Severe Thunderstorms
Cold fronts
 Low pressure systems
 Supercells- powerful self-sustaining
storms characterized by intense updrafts

Lightning
Atmospheric discharge
of electric current
 Heats surrounding air
o
to 30,000 C
 This superheated air
expands rapidly
producing the sound
we call thunder

Wind
Downbursts- violent downdrafts
 Macrobursts- area of 5km or more;
winds of more than 200km/h
 Microbursts- smaller area; deadlier;
harder to predict; winds exceeding
250km/h

Hail
Supercooled water freezes and collides due
to strong updrafts and downdrafts
 Largest hailstone on record- 7 inches wide.
That’s almost the size of a soccer ball!!

Floods
Rising water due to precipitation
 Flash floods- runoff occurring over a
short amount of time

Tornadoes

Violent, rotating column of air that
contacts the ground
Tornado Distribution
Tornado Safety
Chapter 13.3
Tropical Cyclones

Large, rotating, low-pressure storms
Formation of Hurricanes
Classifying Hurricanes
Hurricane Hazards

Storm surges are caused by hurricaneforce winds driving water up and inland