2 ???? What are 2 types of pressure systems? What drives weather patterns?Why is it useful to understand weather patterns?What are some examples of severe weather?
3 High Pressure SystemA high pressure system is a large mass of circulating air with high pressure at its center and lower pressure outside the system.
4 Low Pressure SystemA low-pressure system is a large mass of circulating air with low pressure at its center and higher pressure outside of the system
5 Air MassesAir Masses are large bodies of air with distinct temperature and moisture characteristics.An air mass forms when a large high pressure system lingers over an area for several days.As a high pressure system comes in contact with Earth, the air in the system takes on the temperature and moisture characteristics of the surface below it.
6 Air Mass Classification 5 main air masses impact climate across North AmericaAir masses are classified by their temperature and moisture characteristicsContinental air masses form over landMaritime masses form over water
8 Air Mass Classification Tropical air masses form in the warm equatorial regionsPolar air masses form over cold regionsArctic and Antarctic air masses form near the poles, over the coldest regions of the globe.
9 Front A weather front is a boundary between 2 air masses. Drastic weather changes often occur at fronts.Changes in temperature, humidity, clouds, wind and precipitation are common at fronts.
10 Cold FrontsWhen a colder air mass moves toward a warmer air mass, a cold front forms.
11 Warm frontsA warm front forms when lighter, warmer air moves toward colder, heavier air.
12 Stationary and Occluded Fronts Stationary fronts form when air masses stallOccluded fronts form when a fast moving cold front catches up with a slower moving warm front
13 Severe WeatherThunderstorms have warm temperatures, moisture, and rising air, which may be supplied by a low pressure system.Thunderstorms have a three-stage life cycle: the cumulus stage, the mature stage and the dissipation stage.
15 Thunderstorm StagesThe cumulus stage is dominated by cloud formation and updraftsAfter the cumulus stage, downdrafts, which are air currents moving vertically toward the ground, begin to form.
16 Thunderstorm StagesIn the mature stage, heavy winds, rain, and lightning dominate the area
17 Thunderstorm StagesIn the dissipation stage, updrafts stop, winds die down, lightning ceases, and precipitation weakens.
18 TornadosA tornado is a violent, whirling column of air in contact with the groundTornados form when thunderstorm updrafts begin to rotateTornado Alley is the name given to the area of the central United States that experiences the most tornados
20 Hurricane and Blizzard An intense tropical storm with winds exceeding 119 km/h is a hurricane.A blizzard is a violent winter storm characterized by freezing temperature, strong winds and blowing snow
22 Severe Weather SafetyThe U.S. National Weather Service issues watches and warnings for different types of severe weatherA watch means that severe weather is possibleA warning means that severe weather is already occurring