Thunderstorms
Section 13-1 p 329-333
HOW DO THUNDERSTORMS
FORM ?
•
Three Conditions that are
Responsible
– lots of moisture in lower levels of the
atmosphere
– air has to rise so water vapor can
condense to release latent heat
– Portion of atmosphere where clouds
mature must be unstable
Two types of Thunderstorms
1. AIR-MASS THUNDERSTORMS
When air rises because unequal
heating within one air mass of the
Earth’s surface
2. FRONTAL THUNDERSTORMS
Formed by advancing cold fronts
or in some cases advancing warm
fronts(rare)
Two Common Types of Air-Mass
Thunderstorms
• 1. Mountain Thunderstorms
- result of orographic lifting
- air travels up the side of a Mt.
Two Common Types of Air-Mass
Thunderstorms
2. Sea-Breeze Thunderstorms
- result of extreme temperature
changes in the air over land and air
over water
Two Common Types of Frontal
Thunderstorms
1. Cold Front: cold air pushing warm air
quickly up cold-front boundary
– this motion produces a line of storms
along leading edge of cold front, can be
100’s of km long
– Initial lift from push of cold air
– Can continue long into night
Frontal Thunderstorm – COLD FRONT
Two Common Types of Frontal
Thunderstorms
•
•
Warm Front: warm air slides up and
cold air mass , very mild t-storms can
occur.
Last for short period of time (less than
an hour)
Frontal Thunderstorm – WARM FRONT
CUMULUS STAGE
• Air rises vertically upward creating
updrafts
• Moisture transported to upper portions
of clouds
• Moisture condensed into droplets,
releasing latent heat
MATURE STAGE
• Precipitation Falls cooling surrounding air
• Creation of cool more dense air sinks to
ground with precipitation
• Up & down drafts exist side by side in
cumulonimbus clouds
• Convection cells form developing gusty
winds
DISSIPATION STAGE
• Characterized by the lingering of
downdrafts
• Lack of warm air stops updrafts and the
development of precipitation
• Cloud runs out of previously formed
raindrops