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