Severe Weather
--for those who know enough to come in out of the rain.
Flash flooding
Tornado
High winds
Lightning
Thunderstorm
Hurricane
Winter storms
• Over 500 Americans die each year due to weather related incidents.
• Billions of dollars of damage is done to American homes, farms, cities, and businesses
Rule 1
• Warm air tends to…
Rule 1
• Warm air tends to rise!
Just like warm water and warm magma
Convective uplift—it is forced up by the cooler (and therefore more
dense) fluid around it.
Four reasons air might rise:
1.
2.
3.
4.
Four reasons air might rise:
1. Convective uplift
2. Orographic uplift
3. Frontal wedging
4. Convergence
Four reasons air might rise:
1. Convective uplift
--less dense air is forced up by surrounding air 2. Orographic uplift
--if the land surface rises, the air has to rise 3. Frontal wedging
--an air mass forces its way under another mass 4. Convergence
--when two air masses come together, the only way to go is up
Air Masses
• --like water masses.
• A body of air with its own temperature and humidity
Air Masses
• --like water masses.
• A body of air with its own temperature and humidity
Continental (dry) or Maritime (humid)
Polar (cold) or Tropical (warm)
Front-where two air masses meet
• Cold air mass
(moving southeast)
Warm air mass
Cold air
mass
Warm air mass
(moving east)
Fronts
When a front advances…
When a front advances…
• …one air mass goes over the other.
• The warmer air mass usually goes over the other.
Clouds form…
Clouds form…• …when an air mass
cools enough to allow the water vapor to condense.
• When a warm air mass rises, it starts to cool due to expansion—air pressure is less up there
Cold Air mass
Clouds form…
• …or they don’t.
• Water vapor is clear and colorless--
Air has water vapor.
Clouds have water droplets.
Clouds form…
• …or they don’t.
• Water vapor is clear and colorless--
Air has water vapor.
Clouds have water droplets.
Condensation nuclei make it more likely that water vapor can condense into water droplets
Cumulus clouds make thunderstorms
Cumulonimbus clouds (raining)
Air movement in a thunderstorm
Types of clouds
• Basically—three types are important:
• Stratus
• Cumulus and
• Cirrus
Types of clouds
• Basically—three types are important:
• Stratus
• Cumulus and
• Cirrus
means “a layer”
means “heaped”
means “wispy”
Types of clouds
• Basically—three types are important:
• Stratus
• Cumulus and
• Cirrus
Nimbus = “raining”
Alto = “high”
Combination types take both names
Typ
es o
f cl
ou
ds
Types of clouds
Cirrus clouds
Stratus clouds
Cumulus clouds
Cumulonimbus
CumulonimbusComplete numbskull
Above the clouds
Above the
clouds
Weather occurs in the troposphere
Above the
clouds
Air cools as you get higher
Above the
clouds
Top of Mt. Everest
Above the
clouds
The tropopause is the top of the troposphere
Above the
clouds
Highest clouds
Above the
clouds
Passenger jets fly here
Above the
clouds
Propeller plane altitude
record
Above the
clouds
Jet plane altitude record
Above the
clouds
Air doesn’t get cooler
with altitude in the
stratosphere
Above the
clouds
Ozone layer
Above the
clouds
Cooling with altitude, again
Above the
clouds
NASA gives astronaut’s
wings above the
mesopause
Above the
clouds
Northern lights