1. Weather Patterns Chapter 5 lesson 2

2. Pressure Systems There are 2 types of pressure systems:
High-pressure system – A large body of circulating air with high pressure at its center and lower pressure outside (air sinks in the center)
Low-pressure system – A large body of circulating air with low pressure at its center and higher pressure outside (air rises at center)

3. Air Masses
Air masses – Large bodies of air with distinct temperature and moisture characteristics.
They form when a large high pressure system lingers over an area for several days.
5 types of air masses:
Continental air masses – form over land
Maritime masses – form over water
Tropical air masses – form in warm equatorial regions
Polar air masses – form over cold regions
Arctic and Antarctic air masses – for near the 2 poles (coldest regions)

4. Air Masses

5. Fronts Front – a boundary between 2 air masses. 4 types of fronts:
Cold front – cold air mass moves towards a warmer air mass
Warm front – lighter, warmer air moves towards the cooler, heavier air.
Stationary front – when the boundary between 2 air masses stalls (stays in that place for several days)
Occluded front – when a fast-moving cold front catches up to a slow-moving warm front

6. Fronts

7. Severe Weather
Examples: Tornadoes, Drought, Hurricanes, Floods, Sinkholes, Wildfires, Blizzards, Thunderstorms
Thunderstorms – Warm air rises due to a low-pressure system.
3 stages
Cumulus stage (cloud formations and updrafts, then downdrafts form)
Mature stage (heavy winds, rain, and lightning)
Dissipation stage (storm ceases)

8. Tornadoes
A violent, whirling column of air in contact with the ground.
Form when thunderstorms updraft begin to rotate
Tornado Alley – place in central United States that experience most tornadoes

9. Hurricanes
Intense tropical storm with winds exceeding 200km/h