WEATHER PATTERNSCHAPTER 5 LESSON 2
Weather
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 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)
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
Hurricanes
Intense tropical storm with winds exceeding 200km/h