MOVING AIR MASSES

An air mass is a vast pool of air having similar temperature and moisture characteristics over its horizontal extent. An air mass occupies thousands of square miles of the Earth's surface. Air masses are born in a source region where they take on their characteristic temperature and moisture content.

The jet stream flows from west to east in wave-like patterns.

west east

http://cubanology.com/JetStream.jpg

Meteorologists agree that jet streams may act as a barrier between cold air in the north and warm air in the south. During their meandering, the streams appear to allow some cold air to flow southward and warm air to flow northward. These flows undoubtedly affect the formation of cold and warm air masses.

Which way will the wind blow in Louisiana? Why?

http://www.intellicast.com/WeatherImg/CustomGraphicLoop/sfcmap_None_anim.gif

Which best describes the

direction that high and low pressure area

Move across the United States? Why?

West to East

Fronts are boundaries between contrasting masses of air.

Cold fronts are those where moving cold air slides under warm air. Friction slows the advancing cold air causing a steep slope to the front. The steep slope pushes the air ahead of it rapidly upwards and vertically developed clouds (cumulus) are produced along the front.

Cold Fronts

Cold Air

Heavy Rain often occurs. Cold front Symbol

Warm Air

With greatly contrasting air masses on either side of the front and potentially unstable conditions, violent weather can form. Towering cumulonimbus clouds are common along cold fronts producing intense downpours of rain lasting for a relatively short period of time. Tornadoes can form under the most extreme conditions ahead of an advancing cold front.

A warm front is where moving warm air pushes over cold air. As with a warm front, you experience a drop in the atmospheric pressure as the front approaches. The warm front slopes gently up into the troposphere that has a direct bearing on the kinds of clouds that are produced. As the warm air behind the front collides with the cooler air ahead, the warmer less dense air is forced to glide upward.

Warm Fronts

Warm AirCool Air

Light or moderate Rain often occurs. Warm front Symbol

Once the warm front passes your location you'll notice an increase in temperature and air pressure. Soon the stratus clouds of the warm front give way to broken and clearing skies. As the warm sector moves into your location you will notice an increase in the humidity of the air

Figure WS.4 Front Symbols

Air particles moving from areas

of high pressure to areas of low

pressure.

WIND

HH

L

Which kind of FRONT?

Moving cold air slides under warm air.

COLD FRONT

Which kind of FRONT?Add to notes in correct front

Moving warm air pushes over cold air.

WARM FRONT

Which kind of FRONT?Add to notes in correct front

This symbol:

WARM FRONT

Which kind of FRONT?Add to notes in correct front

This symbol:

COLD FRONT

Which kind of FRONT?Add to notes in correct front

Heavy Rain often occurs.

COLD FRONT

Which kind of FRONT?Add to notes in correct front

Light or moderate rain precipitation can occur.

WARM FRONT

Air particles moving from areas

of high pressure to areas of low pressure

describes….

WIND