Air Masses and Air Masses and Fronts Fronts

Synoptic Weather MapsSynoptic Weather Maps

What is an Air Mass?What is an Air Mass?

Air masses are large bodies of air which have Air masses are large bodies of air which have similar similar temperature and moisture temperature and moisture characteristicscharacteristics..

Air masses form when air stays over a region Air masses form when air stays over a region (called the (called the source regionsource region) for several days. ) 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 Latitude determines temperaturetemperatureMoisture determined by whether Moisture determined by whether it forms over oceans or it forms over oceans or continentscontinents

Fronts – boundary that separates Fronts – boundary that separates 2 air masses with different 2 air masses with different temperaturestemperatures

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 Winds spiral clockwise out of the High and counterclockwise into High and counterclockwise into the Lowthe LowFronts are low pressure – lousy Fronts are low pressure – lousy weatherweatherAfter the front passes – happy After the front passes – happy weatherweather

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

Warm Front – longer, Warm Front – longer, steady precipitationsteady precipitation

Occluded FrontOccluded Front

Stationary FrontStationary Front

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

Weather Changes after Weather Changes after Fronts PassFronts Pass

2 TOTALLY different air masses so a 2 TOTALLY different air masses so a change in weatherchange in weather

Temperature changesTemperature changes Wind direction changesWind direction changes Wind velocity changesWind velocity changes Dew Point changesDew Point changes Barometer falls when front Barometer falls when front

approaches and rises after it passesapproaches and rises after it passes

How Mid-How Mid-Latitudes Latitudes LowsLows(occlude(occluded fronts) d fronts) FormForm

Counter-Clockwise

rotation

Counter clockwise rotation into Low

Storm moves northeast due to prevailing winds