6 4 4 AIR MASSES FRONTS PRESSURE SYSTEMS

6. 4. 4: AIR MASSES, FRONTS, PRESSURE SYSTEMS, & STORMS 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.

� � � Frontsthe 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.

Comparing Cold Fronts with Warm Fronts � 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 �

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.

Locate the 4 types of fronts on this weather map.

Be a Weather Forecaster � You are planning to travel to Alabama in 2 days. The high temperature there for today is � 68º 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.

High Pressure Winds Low Pressure Winds

� � 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 More Tracking Hurricane Simulation

Other Weather: fair weather, showers, blizzards, droughts, snow, ice storms, etc.

� � � � How Weather Systems Mo ve From Place to Place Streamline Understanding the Weather Streamline 15 min Heat, Wind, & Pressure Streamline 15 min The Magic School Bus Goes on Air Streamline 27 min The Magic School Bus Kicks Up a Storm Streamline 29 min Raging Planet: Hurricane Streamline 24 min Weather Smart: Hurricanes Streamline 15 min Hurricanes, Tornados, & Thunderstorms Streamline 24 min

� � � Natural Phenomena: Hurricanes, Tornadoes, & Other Weather Streamline 15 min Links: Weather Wiz Kids Awesome Site: http: //www. weatherwizkids. com/wind 1. htm Ware Shoals Weather: http: //www. weather. com/weather/local/29692? lswe=2 9692&lwsa=Weather. Local. Undeclared&from=whatwhe re FEMA for Kids: http: //www. fema. gov/kids/ Weather for Kids: http: //www. eo. ucar. edu/webweather/ KIDSSTORM: http: //skydiary. com/kids/

� � � � Weather Maker: http: //www. scholastic. com/kids/weather/ National Weather Service: http: //www. nws. noaa. gov/om/reachout/kidspage. shtml Extreme Weather: View a tornado: http: //www. nws. noaa. gov/om/reachout/kidspage. shtml Hurricane Simulation: http: //www. npr. org/news/specials/hurricane/ap/ Weather Songs: http: //www. wxdude. com/guide. html KIDS WEATHER INFO: http: //www. kidinfo. com/Science/weather. html Planet Pals: http: //www. planetpals. com/weather. html