1. What is meteorology?
• Meteorology: the study of atmospheric
processes and events….”meteor” means
high in the air

2. What is the difference between
weather and climate?
• Weather: current state of the atmosphere….it
changes daily!!!
• Climate: long-term variations in weather over a
geographic area
– The angle (and intensity) of sunlight is the major factor
that determines climate
• More direct at Equator = tropics
• More indirect at Poles = arctic region

3. What is an air mass?
• Air mass: large body of air that is
influenced by the area over which it forms
– Continental tropical (cT): warm and dry
– Maritime tropical (mT): warm and humid
– Continental polar (cP): cold and dry
– Maritime polar (mP): cold and humid
– Arctic (A): same as cP, but MUCH colder!!

4. What is an air mass?
• All of these air masses MOVE and
INTERACT, which causes WIND,
STORMS, and all other WEATHER!!!

5. What are weather systems?
• There are many types of weather systems….
• 1) Permanent wind systems
– Trade winds
– Prevailing winds
– Polar easterlies

6. What are weather systems?
• 2) Jet streams: narrow bands of high-altitude,
fast-moving winds
• 3) Fronts: narrow region separating two
DIFFERENT air masses
– Cold fronts: causes clouds, rain
– Warm fronts: causes clouds, rain
– Stationary fronts: two fronts collide and “stall”
– Occluded fronts: warm air mass trapped between two
cold air masses.

7. What are weather systems?
• 4) Pressure systems: cause pressure
changes that allow air to move in a rotating
motion
– High pressure system: usually good weather
– Low pressure system: usually stormy weather

8. Weather
Weather: A Brief Introduction:
Weather is short-term atmospheric conditions in an area. It is typically
considered in hours or days.
Much weather activity is due to interactions between leading edges
or fronts of moving masses of warm or cold air.
Jet streams are near the top of the troposphere and circle the
Earth. They have a strong influence on weather patterns.

9. Weather
A cold front is an advancing
mass of cold air that
stays close to the
ground. It is often
associated with
thunderstorms and high
winds. Cooler, clear
weather is the result.

10. A warm front is the
boundary between a warm
mass of air and the cooler
air it replaces. It often
results in cloudy, rainy days.
Weather

11. What causes precipitation?
• Coalescence: small water droplets
combining to form larger droplets that then
FALL out of the cloud by the act of gravity

12. Weather
Changes in atmospheric
pressure also affect
weather.
Atmospheric pressure is
greater near the earth's
surface. A high-pressure
air mass (a high “H”)
contains cool, dense air
that warms as it descends.
Fair weather is the result.
A low-pressure air mass (a
low “L”) produces cloudy,
stormy weather. The
center of the low rises due
to the low density of air. If
condensation nuclei are
present with cooler
conditions, there will be
rain.

13. What are thunderstorms?
• At any point in time, about 2,000 thunderstorms
are occurring on Earth!!!
• 3 conditions are needed for formation…
– 1) Lots of moisture in lower atmosphere
– 2) Air must be lifted/cooled so moisture can condense
into liquid water
– 3) The moist air mass must be unstable so it can
continue to rise (so that the cloud gets big!)

14. What are thunderstorms?
• 3 stages of a thunderstorm…
– 1) Cumulus stage: air rises and cools so that
moisture condenses into liquid drops
– 2) Mature stage: precipitation forms and
downdrafts/updrafts (winds) form
– 3) Dissipation stage: winds/energy/
precipitation “run out” and the thunderstorm
ends

15. What are thunderstorms?
• Air-mass thunderstorms (temperature
differences between 2 air masses)
– Mountain thunderstorms
– Sea-breeze thunderstorms
• Frontal thunderstorms (produced by
advancing cold fronts)

16. What other weather occurs along
with thunderstorms?
• Supercells: the most SEVERE
thunderstorms with high winds
• Lightning: electricity caused by rapid air
movement within cumulonimbus clouds
– 5 times hotter than the sun!!!

17. Supercell Thunderstorm

18. What other weather occurs
along with thunderstorms?
• Hail: frozen water droplets that form within
clouds
• Floods: occur when storm systems move
SLOWLY
• Tornadoes: occur when wind speed and direction
change suddenly
– Fujita scale: F1 (least) to F5 (most severe)

19. Extreme Weather
Tornadoes and tropical
cyclones are extremes
of weather that cause
much damage.
Tornadoes form over
land, and tropical
cyclones form over
warm ocean waters.
Tornadoes are most prevalent
in the United States and
Australia. They are
funnel-shaped clouds
that form when dry, cold
air from Canada meets
humid air from the Gulf
of Mexico, (tornado
alley) Oklahoma City
experienced 58
tornados in one day .
Most tornadoes occur in
the spring.

20. Tropical Storms
• Tropical cyclones: large, rotating, low-
pressure storms

21. Tropical Storms
• Steps in tropical storm formation…
– 1) Warm ocean water evaporates, then
condenses to form clouds
– 2) Low pressure area develops in the middle of
clouds
– 3) Pressure differences cause rotating winds to
form

22. Tropical Storms

23. Tropical Storms
• Saffir-Simpson scale: categorizes
hurricanes
– Category 1 (weak)  Category 5 (strong)
– Storm Surge: winds drive a mound of ocean
water over land

24. Tropical cyclones
are formed by low-
pressure cells of air
moving over warm
tropical seas.
Cyclones forming
over the Atlantic
Ocean are called
hurricanes; those
forming over the
Pacific Ocean are
called typhoons.
Forces of
hurricanes and
typhoons can kill
and injure people
and damage
property.
Hurricanes also flush out excess nutrients from land runoff, dead
seagrasses, and rotting vegetation from coastal bays and marshes. This
results in increased productivity of commercially important species of
shellfish and fish as well as reduced explosive growth of algae.
Extreme Weather

25. Other Weather Events
• Droughts: extended periods of well-below-normal
rainfall
• Heat waves: extended periods of hot weather
• Cold waves: extended periods of cold weather
– Wind-chill factor: takes into account the effect of
winds on temperature

26. How is weather analyzed?
• Isobar maps: “topographic maps” for
pressure differences
– The closer together the ‘isobar lines’, the faster
the wind speed!!!
– How accurate are weather forecasts?
• ACCURATE from 1-3 days
• INACCURATE from 4-7 days (or more)

27. Weather Data
• Thermometer: measures temperature (a
liquid expands when heated and fills up a
tube)
• Barometer: measures air pressure
– Pressure drop = future storm!

28. Weather Data
• Anenometer: measures wind speed
• Hygrometer: measures humidity
• Ceilometer: measures height of cloud
layers

29. Weather Data
• Radar: radar waves bounce off of large
raindrops (but not small droplets within
clouds)
• Satellite: tracks clouds (but not necessarily
rain)

30. Image Source
www.noaa.com