1. Weather Instruments These are the instruments that measure the primary
weather variables in our atmosphere
Barometer
Rain gauge
Thermometer
Anemometer
Sling psychrometer

2. Most sudden changes in the weather are a result of Air Masses
An air mass is defined as:
a large parcel of air
that has taken on the characteristics of the surface
over which it has been sitting
When an air mass sits over a surface of the earth
It can acquire 2 primary properties
1. temperature
2. moisture content
How many possible combinations of air masses could
you have using only these 2 variables?

3. 1.warm and moist 2. warm and dry 3. cold and moist 4. cold and dry
What type of surface would these air masses form over?

6. Cold air mass

7. cP mT cT

8. The leading edge of an air mass is called a
FRONT
The symbols point
in the direction the
air is moving

9. COLD FRONT
COLD air mass advances on a WARM air mass, pushing forward into the warm air

10. WARM FRONT WARM air mass advances on a COLD air mass.
Since the cold air is more dense, the warm air mass is forced to rise as it pushes forward

11. OCCLUDED FRONT
TWO cold fronts approaching each other are separated by a warm air mass
As the two cold fronts near each other, the warm front is pushed up over the cold front and off the ground

12. Stationary Front
A warm air mass and a cold air mass are adjacent to each other, but do not move

14. Front The leading edge of an air mass is called a:
Here is a surface map showing a cold front
that has just moved through the midwest

15. cold front side view The following things usually
happen as a cold front approaches
and moves past a location:
cold front side view
A rapid increase in cloud cover, usually tall cumulous or
cumulonimbus type
2. A rise in the wind velocity, and shift in direction from
south to north
3. Brief heavy precipitation or thunderstorm possible
4. A rapid fall in pressure, followed by a gradual rise
5. A sharp drop in temperature
Notice the high angled slope
or pitch

16. Simulation at high speed

17. Warm front side view 4. A gradual increase in temperature
The following weather changes
usually occur as a warm front
approaches
1. A steady drop in pressure
2. Cirrus clouds are first indication
of approaching warm front
3. A gradual increase in clouds
until entire sky is covered
4. A gradual increase in temperature
5. Long term light to moderate
precipitation
6. A shift in the winds from
north to south

18. A warm front is a much
gentler slope or pitch
Changes in the weather
Occur much more slowly