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Air Masses and Fronts. Types of Air Masses. Tropical Polar Maritime Continental. = Warm = Cold = Ocean = Land. How do Air Masses Move. ??????????????????????? Prevailing Westerlies are our major influence. Fronts. Are an area where two types of weather collide Four types
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Types of Air Masses • Tropical • Polar • Maritime • Continental = Warm = Cold = Ocean = Land
How do Air Masses Move • ??????????????????????? • Prevailing Westerlies are our major influence
Fronts • Are an area where two types of weather collide • Four types • Cold Fronts • Warm Fronts • Stationary Fronts • Occluded fronts
Cold Fronts • Cold air hits slow warm air • Severe weather producer
Warm Fronts • Warm air pushes into colder air • Typically produces light rains
Stationary Fronts • Two air masses hit and neither one has enough power to push the other out of the way.
Occluded Front • Warm air is cut off from the surface
Cyclones and Anticyclones • Cyclones • Low pressure centers • Winds pull toward the center • Rotate counter clockwise • Produce stormy weather
Anticyclones • High pressure center • Winds blow out • Clockwise rotation
Storms • Defined as a violent disturbance in the atmosphere • How do they form?? • Need a large cumulonimbus cloud • Often called thunderheads • Strong up drafts • Moisture • Hot and cold air
Thunder and Lightning • These two are closely related • You can not have one with out the other. • Lightning causes thunder. • Lightning is nothing more than static electricity.
Thunderstorm Safety • Stay away from tall objects • Avoid metal objects • Avoid telephones, electrical appliances, and anything plumed to the outside • Golf courses are the number one place people get struck by lightning. • Why??
Tornadoes • Rapid whirling funnel shaped cloud • Most are not on the ground for more than 15 min • Most only average 5-10 WHY??? • Wind speeds near 100 to 150 miles per hour
How do Tornadoes Form? • Found in low heavy Cumulonimbus clouds • Can be the same cloud that produced a thunderstorm • Green clouds are common • A back chilling calm followed by a rapid change in wind direction or speed • Good hints that a tornado is brewing
Tornado Facts • Over 800 occur every year in the U.S. • Oklahoma, Kansas, and Nebraska are the centers of what is known as tornado alley • Our current warning system usually give people only a few minutes to find safety
More facts and The Fajita Scale • http://www.tornadoproject.com/fscale/fscale.htm
Tornado Safety • Have been known to throw objects over 30 miles • Tornado Watch is a way for the weather service to tell people to watch up coming storms for severe tornado activity • Tornado Warning means a tornado has been sited and confirmed in your area take cover immediately
Safest place is in a basement • Typically in the corner or under a stairwell • If you do not have a basement then in the bathroom tub with a mattress or heavy blankets over you is best. • What should you have in your tornado shelter • Water, batteries, snack food, radio, flashlights, and blankets
Hurricanes • Major tropical storms • Wind speeds that top 350 mph • In the pacific they are called typhoons • Are very similar to tornadoes just on a larger scale • Are so massive they can control their own weather.
How do Hurricanes Form • Need lots of warm water • Need a low pressure cell • Warm water is its fuel • The longer is stays over warm water the stronger it will become • This is why they do not last long once they have hit land • Eye of the hurricane is very calm • In large hurricanes the eye has been recorded as a bright warm sunny day
Can cause all kinds of damage • Mainly due to wind • Storm surge is also a problem • Hurricane safety • Costal communities must evacuate • Only true way to be safe, although some people choose to stay. Unfortunately looting is a problem and people want to protect their property. • Some who live inland can choose to wait it out like sitting through a very long tornado
Flash Floods • Commonly happens with severe weather • So much water falls in such a short time that a river leaves its banks • Can happen very quickly • Safety tips • Stay away from flood waters • Stay on high ground • Stay away from electric poles
Predicting the weather • Done by Meteorologists • People who study weather • Make predictions based on observations • Clouds • Winds • Technology • Weather balloons • Satellites • Computer models
Weather Maps • Meteorologists use this to show weather • Isobars - lines of equal pressure • Isotherms - lines of equal temperature • See pg 587 • The further we get from the current day the less accurate we get
Weather Phenomenon • El Nino -- Unusual warming of the pacific ocean • La Nina -- Unusual cooling of the pacific ocean