Air Masses and Fronts Synoptic Weather Maps

What is an Air Mass? Air masses are large bodies of air which have similar temperature and moisture characteristics. Air masses are large bodies of air which have similar temperature and moisture characteristics. Air masses form when air stays over a region (called the source region) for several days. Air masses form when air stays over a region (called the source region) for several days. Air masses that form over water will be moist. Air masses that form over water will be moist. Air masses that form over land will be dry. Air masses that form over land will be dry.

c continental = dry m marine = moist A = Arctic P = Polar T = tropic

Latitude determines temperature Moisture determined by whether it forms over oceans or continents

Fronts – boundary that separates 2 air masses with different temperatures

WINDS FLOW COUNTERCLOCKWISE IN TO THE LOW PRESSURE SYSTEM – RISING AIR WINDS FLOW CLOCKWISE OUT OF THE HIGH PRESSURE SYSTEM – SINKING AIR

Winds spiral clockwise out of the High and counterclockwise into the Low Fronts are low pressure – lousy weather After the front passes – happy weather

Cold Front a. short-lived thunderstorms b. move faster than warm fronts

Warm Front – longer, steady precipitation

Occluded Front

Stationary Front A stationary front occurs when the air masses on either side of the front are not moving toward each other. A stationary front occurs when the air masses on either side of the front are not moving toward each other.

Weather Changes after Fronts Pass 2 TOTALLY different air masses so a change in weather 2 TOTALLY different air masses so a change in weather Temperature changes Temperature changes Wind direction changes Wind direction changes Wind velocity changes Wind velocity changes Dew Point changes Dew Point changes Barometer falls when front approaches and rises after it passes Barometer falls when front approaches and rises after it passes

How Mid- Latitudes Lows (occluded fronts) Form Counter- Clockwise rotation

Counter clockwise rotation into Low Storm moves northeast due to prevailing winds