2What is an Air Mass?An AIR MASS is a large body of air that takes on the TEMPERATURE and HUMIDITY (moisture) of a regionUsually THOUSANDS of miles in diameterForms over a source region with relatively stable conditionsNamed for the SOURCE REGION (where it comes from)
3Two Air Masses: each air mass has roughly the same temperature and humidity
4Types of Air Masses: Named by where they come from! POLAR: source region (colder air mass) (P)TROPICAL: source region (warmer air mass) (T)(basically north or south)**************************************MARITIME: Source region (formed over the ocean)(m)CONTINENTAL: Source region (formed over land) (c)(over ocean or land)
5Types of Air Masses:Maritime Tropical (mT): form over the tropical oceans, very humidMaritime Polar (mP): form over cold ocean areas, cool but humid airContinental Tropical (cT): Hot, dry , air masses from the southwestContinental polar (cP): cool or cold dry air
6Can you find the different continental air masses?
7These circles enclose air masses. What is the name of a line that surrounds an area of EQUAL TEMPERATURE? ISOTHERM
8QUESTION:WHICH AIR MASS DO YOU THINK WOULD PRESS DOWN ON THE EARTH MORE?a COLD AIR MASS or a WARM Air MASS?WHY?
9How do the air masses move? WINDS!Uneven heating of the earth’s surface causes convection currents which cause differences in pressure, which causes winds.Prevailing westerlies generally push the air masses from WEST EAST
11What is a FRONT?A weather FRONT forms when two unlike air masses meet (cold and warm air masses)Because of the difference in TEMPERATURE and DENSITY of the air masses, the meeting results in storms and changing weather.Fronts are named by which air mass is MOVING!
12FOUR FRONTS COLD FRONT- cold air mass moving WARM FRONT- warm air mass movingSTATIONARY FRONT – neither air mass movingOCCLUDED FRONT-warm air mass caught between two cold air masses
13COLD FRONT Colder, more dense air. Warmer, less dense air. IF AIR MASS #1 MOVES TOWARDS AIR MASS #2 COLD FRONTCOLD FRONT SYMBOL:
14COLDFRONT Colder, more dense air. Warmer, less dense air. Cold Air moves in quickly to replace warmer airWarmer air will rise, cool, then form large, CUMULONIMBUS CLOUDS (the thunderstorm kind)Usually cause short lived, violent STORMS (rain, snowfall)
15COLD FRONT DIAGRAM:What happens to the temperature after a cold front moves though an area?
16WARM FRONT Air Mass #1 Colder, More Dense Air Air Mass #2 Warmer, Less dense AirIF AIR MASS #2 MOVES TOWARDS AIR MASS #1 WARM FRONTWARM FRONT SYMBOL:
17WARM FRONT Air Mass #1 Colder, More Dense Air Air Mass #2 Warmer, Less dense AirWARM FRONTWarm Air Mass moves in to replace colder air massMoves SLOWER than Cold frontClouds that form are thinner (not puffy)Usually causes LIGHTER, but LONGER periods of precipitationIn winter, brings snow.
18WARM FRONT DIAGRAM: WARM AIR MASS collides with a cold air mass. Warm air slowly moves OVER cold air. Longer rain storms.
19STATIONARY FRONT Cold Air Mass Warm Air Mass A COLD AIR MASS AND A WARM AIR MASS MEET, BUT NEITHER HAS THE FORCE TO MOVE THE OTHERWARM FRONT SYMBOL:
20Comparing Warm and Cold 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.
34Be 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.Weather Fronts
35Be a Weather Forecaster There is a cold front approaching. The temperatures will probably be cooler behind the front.
36Be a Weather Forecaster 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.MAP TAPWeather Fronts