Transcript Weather Patterns Chapter 15-2

Weather Patterns
Chapter 15-2
I. Changes in Weather
A. Air Masses
1. An air mass is …
… a large body of air that has the same
properties as the surface it develops over.
2. For example …
a. Dry air mass over land
Moist air mass over water
b. Warm air mass over the tropics
Cold air mass over the poles
3. Daily weather is due to …
… movement of air masses.
B. Pressure Systems
1. Three things that determine atmospheric
pressure are …
-Temperature
-Density
-The amount of water vapor
2. High pressure is the result of …
Descending (Sinking) Air
3. High pressure brings good weather because …
Sinking air makes it difficult for air to rise
and clouds to form.
C. Fronts
1. Low pressure systems form …
… along the boundaries of air masses.
2. A Front is …
… the boundary between two different air masses.
3. You would expect to see …
storms and precipitation
as a front passes overhead.
4. Air movement as fronts collide
5. The winds rotate counterclockwise as a result of …
the coriolis effect.
D. Four types of fronts
1. Warm Front
a. A Warm front occurs when …
… less dense, warm air slides over a departing
cold air mass.
b. The precipitation associated with a warm front …
… would be a wide band of precipitation.
c. The clouds you would expected to see would be
…cirrus.
2. Cold Front
a. In a cold front …
… a colder air mass pushes under a warm air
mass and forces warm air up on a steep
curve.
b. A cold front produces …
… a narrow band of violent storms.
c. The type of clouds it produces would be …
… cumulus and cumulonimbus.
3. Occluded Front
a. An occluded front results from …
… two cool air masses crashing together
and forcing warm air between them to rise.
b. You would expect to see …
… strong winds and heavy precipitation.
4. Stationary Front
a. A stationary front occurs when …
… pressure differences cause warm and cold
fronts to stop moving.
b. In a stationary front you expect to see …
… light winds and wide spread precipitation
across the frontal region.