Air masses Are huge bodies of air, with similar temperatures & moisture. They are formed over water or land in tropical or polar regions. Air masses move. When they form, the temperature or humidity in them results in different weather conditions.

 Fronts the boundary between 2 air masses when they collide  Depending upon the air masses involved 4 fronts can occur:  4 kinds of fronts:  Cold front  Warm front  Occluded front  Stationary front

Cold Front:  Results in Violent Weather  Represented by the following symbol on a weather map:  Shown on a weather map by a blue line with triangles pointing the direction the cool air is moving.  A cold air mass is replacing a warmer air mass.

Warm Front:  Steady gentle rain showers-  Represented by the following symbol on a weather map:  Shown on a weather map by a red line with half circles pointing the direction the warm air is moving.

 Cold fronts move faster than warm fronts.  The weather activity in a cold front is often violent and happens directly at the front.  Cold fronts have sudden gusty winds high in the air creating turbulence.  The weather activity in a warm front generally happens before the front passes.  In a warm front the cloud formation is very low often creating situations of poor visibility.  See the video See the video

Stationary Front: “stand off”  A front that stops moving or is moving very slowly.  Shown on a weather map with alternating red semicircles pointing away from the warm air and blue triangles pointing away from the cold air.  Clouds and fog form. It may rain or snow, can bring days of cloudy weather. 

Occluded Front:  When a warm front is trapped by 2 cold fronts.  gentle rain, violent storm, gentle rain  Shown on a weather map by a purple line with alternating triangles and semicircles pointing the direction the front is moving.

 You are planning to travel to Alabama in 2 days. The high temperature there for today is  68 º F. Use the map to help you predict whether the temperature in Alabama will increase, decrease, or stay the same. Explain why you think so.

There is a cold front approaching. The temperatures will probably be cooler behind the front.

 Of course, meteorologists (weather forecasters) use much more data than fronts and air masses to help them forecast the weather more accurately. But any forecast is just a prediction of what might happen. Even with the best data, weather forecasts can be wrong.

 High/Low Pressure Systems  Warm air rising or cold air sinking combined with the spinning of Earth causes the air to spin forming high and low pressure regions.

 High pressure systems usually signal more fair weather with winds circulating around the system in a clockwise direction.  Low pressure systems with counterclockwise circulating winds often result in rainy and/or stormy weather conditions.

 Storms Severe weather conditions - occur when pressure differences cause rapid air movement. Conditions that bring one kind of storm can also cause other kinds of storms in the same area.  Thunderstorm is storm with thunder, lightning, heavy rains and strong winds; form within large cumulonimbus clouds; usually form along a cold front but can form within an air mass

 Tornado is a rapidly whirling, funnel- shaped clouds that reaches down from a storm cloud; the very low pressure and strong winds can cause great damage to people and property; are likely to form within the frontal regions where strong thunderstorms are also present

 Hurricane is a low pressure tropical storm that forms over warm ocean water; winds form a spinning circular pattern around the center, or eye, of the storm; the lower the air pressure at the center, the faster the winds blow toward the center of the storm.  Hurricane Tracking Hurricane Tracking  More Tracking Hurricane Simulation More TrackingHurricane Simulation

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 Weather Maker:   National Weather Service:  html html  Extreme Weather:  View a tornado: html html  Hurricane Simulation:  Weather Songs:   KIDS WEATHER INFO:   Planet Pals: 