Download Ch 5_2 _self made - Mater Academy Lakes High School

Weather
WEATHER PATTERNS
CHAPTER 5 LESSON 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)
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)
Air Masses
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
Fronts
Severe Weather
 Examples: Tornadoes, Drought, Hurricanes, Floods,
Sinkholes, Wildfires, Blizzards, Thunderstorms
 Thunderstorms – Warm air rises due to a lowpressure system.

3 stages
Cumulus stage (cloud formations and updrafts, then downdrafts
form)
 Mature stage (heavy winds, rain, and lightning)
 Dissipation stage (storm ceases)

Tornadoes
 A violent, whirling column of air in contact with the
ground.



Form when thunderstorms updraft begin to rotate
Measured with the Fujita scale
Tornado Alley – place in central United States that experience
most tornadoes
Hurricanes
 Intense tropical storm with winds exceeding
200km/h