Air Masses and Weather Fronts

Why do we need to know anything about weather fronts? When we look at weather fronts we can see what type of weather we are having. We can prepare for severe weather when looking at the types of weather fronts.

A boundary between two distinct air masses is called a weather front .

Weather Front Symbols ????Which is Which????

Types of Fronts There are 4 types of fronts: Cold Fronts Warm Fronts Stationary Fronts Occluded Fronts

Symbol: Warm Fronts A warm front occurs when a less dense air mass rides up over a more dense air mass.

Clouds, Storms, and rain accompany warm fronts. Moving warm air mass collides with a slowly moving cold air mass Warm Front Animation: http://ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act/gifs/fpr4.gif http://earthsci.org/processes/weather/weaimages/2e.gif

Cold Fronts Symbol: A cold front occurs when a more dense air mass pushes under a less dense air mass.

Cold air is dense and tends to sink, while warm air is less dense and tends to rise. Rapidly moving cold air runs into a slowly moving warm air mass and pushes the lighter warm air upward. Cold front animation: http://ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act/gifs/fpr2.gif http://earthsci.org/processes/weather/weaimages/2g.gif

Cold Fronts can cause heavy snow or ice if there is enough water vapor in the air.

Occluded Front Symbol: A warm air mass is caught between two cooler air masses

Occcluded Fronts: The two cooler air masses meet in the middle and may mix. The warm air mass is cut off (or occluded) from the ground. http://www.uwsp.edu/geo/faculty/ritter/images/atmosphere/weather/cold_occlusion.gif

Stationary Front Symbol: Warm air mass and cold air mass meet Neither has enough force to move the other so they just stay in the same place. Where they meet, water vapor in the warm air condenses into rain, snow, fog or clouds Can stall out for days

Stationary Fronts: Stationary Front Animation: http://www.usatoday.com/weather/tg/wsfront/wsfront.htm Unlike a fast-moving front, Stationary fronts often bring several days of cloudy, wet weather that can last a week or more.