FRONTS

What is an air mass? A large body of air having nearly uniform conditions of temperature and humidity at any given altitude.

Air Masses Warm air forms over tropical regions near the equator. T- Tropical Cold air forms over polar regions. P- Polar Wet air masses form over water m- maritime Dry air masses from over land. c- continental

Moisture content is noted by the first letter. m – maritime – wet Air masses Moisture content is noted by the first letter. m – maritime – wet c – continental – dry Temperature is noted by the second letter. P – polar – cool T – tropical - warm

Types of Air masses Continental Polar (cP) , “cold and dry” closer to the Poles over land-locked regions. Continental Tropical (cT), “warm and dry” closer to the Tropics over land-locked regions. Maritime Polar (mP), “cold and damp” closer to the Poles over water. Maritime Tropical (mT), “warm and humid” closer to the Tropics over water.

Fronts The advancing edge of a mass of cold or warm air. front- the area where two air masses meet and do not mix (from military language meaning a battle area where opposing armies meet to fight) A front always causes a change in weather because the air masses that meet do not mix and their different densities and air pressure produce wind, clouds and temperature changes.

Fronts A front is a boundary between air masses. Cold front Warm front Four types of fronts and map symbols The directions that the bumps face is the direction the front is moving. Cold front Warm front Stationary front Occluded front

Cold Fronts When a fast moving cold air mass runs into a slow moving warm air mass and the thicker cold air slides under the lighter warmer air.

Bring thunderstorms, rain or snow. Cold Fronts Bring thunderstorms, rain or snow. Most tornadoes develop from thunderstorms on the edge of a cold front. Cold front followed by sunny cooler drier air. http://www.mesoscale.iastate.edu/agron206/animations/05_cnWfronts.html

What will happen if the warm air mass contains only a little water vapor? Warm air with little water vapor may be accompanied by ONLY cloudy skies. If there is a lot of water vapor in the warm air, heavy rain(thunderstorms)or snow may fall.

Warm Fronts When a moving warm air mass collides with a slowly moving cold air mass and the warm air moves over the cold air.

If warm air is dry, scattered clouds form. If warm air is humid, showers and rain fall along the front. In winter warm fronts can bring snow. If warm air is dry, scattered clouds form. Because warm fronts move more slowly than cold fronts, weather may be more foggy or rainy for several days. After a warm front passes, the weather is likely to be warm and humid. http://www.mesoscale.iastate.edu/agron206/animations/05_cnWfronts.html

Stationary Fronts When a cold air mass and warm air mass meet, but neither air mass has enough force to move the other air mass.

Stationary Fronts Many days of cloudy, wet weather. http://www.youtube.com/watch?v=VwI1NmESxss

Occluded Fronts When a warm air mass is caught between two cooler air masses and the thicker cold air masses move underneath the thinner warm air mass and push it upward.

Occluded Fronts Brings cool temperatures with large amounts of rain or snow http://www.youtube.com/watch?v=4gc7puH279s

Cold Front, Warm Front and Occluded Front Animation http://www.phschool.com/atschool/phsciexp/active_art/weather_fronts/ http://www.classzone.com/books/earth_science/terc/content/visualizations/es2002/es2002page01.cfm?chapter_no=visualization

Quiz Describe a maritime polar (mP) air mass, in terms of moisture and temperature. 2. What is the name of an air mass that forms over water? 3. What is the name of an air mass that forms over land? 4. What is the name of an air mass that forms in a cold region? 5. What is the name of an air mass that forms in a warm region? 6. Describe a continental tropical (cT) air mass, Moisture and temperature.

Quiz 7. The boundary between two air masses is called a ______________________. 8. A cold air mass meets and pushes a warm air mass out of the way. What type of front am I? 9. A warm air mass is trapped between to cold air masses. What type of front am I? 10. A warm air mass meets and pushes a cold air mass out of the way. What type of front am I? 11. I am a front that brings drizzly rain and am followed by warm clear weather. Name me. 12. A cold air mass meets a warm air but neither is very strong. They are separated and many days of wet , cloudy weather occur.

Which types of fronts can you find on this map?