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CP Sci 9- 1st Sem.

Gen Chem - 1st Sem.

Fronts & Lows 


    1.    Describe the weather conditions associated with different types of fronts.

    2.    Describe the life cycle of a mid-latitude low.

Key Terms:

    front        cold front        warm front        occluded front        stationary front

Notes: (20-2)

As we stated earlier, weather is constantly changing as different air masses interact with each other around our globe.  Nowhere is this seen as much as is in the mid-latitudes where the cold air from the polar regions (cA, cP, & mP) mix with warm air from the equator (mT & cT).   The boundary that separate the different air masses is called a front.  The following are basic characteristics of a front.

bulletless dense warm air moves over the more dense cold air
bulletwedge shaped
bulletsteepness of the slope indicates the severity of the weather
bulletusually brings clouds and possibly precipitation

Cold Fronts   

A cold front is characterized by cold dense air that is advancing on warmer less dense air.

bulletcold air slides under the warm air forcing it upward
bulletthe rising warm air quickly condenses as it rises
bulletthe type of air in the warm front determines the type of weather (warm saturated air brings thunderstorms)
bulletcumulous and cumulonimbus clouds
bulletheavy brief showers
bulletsince the advancing front is slowed by friction, cold fronts usually have steep slopes
bulletcold dry weather usually accompanies the passing of the front

Cross-section of a cold front    Cold front

(www.bom.gov.au/info/ftweather/ images/cold_front.gif)

Warm Fronts   

A warm front is characterized by warm less dense air that is advancing on colder dense air.

bulletwarm air slides over the cold air 
bulletthe rising warm air slowly condenses as it rises over the colder air
bulletcirrus clouds indicate an advancing warm front
bulletcirrostratus clouds follow is there is sufficient moisture
bulletthe type of air in the warm front determines the type of weather 
bulletif the warm air is saturated alto and nimbostratus clouds bring prolonged rain showers
bulletwarm weather usually follows the front passing

(atschool.eduweb.co.uk/.../ppt/ depression/HTML/img004.gif)

Occluded & Stationary Fronts

bulletoccluded fronts occur as the faster moving cold front overtakes the slower moving warm front
bulletcan cause clouds and brief precipitation
bulletstationary fronts occur as frontal systems are not moving
bulletassociated with flooding

(earth.usc.edu/.../weather/images/ massesfronts/nineten.jpg)

Weather and Pressure Systems

bulletHigh pressure
bulletwarm days and cold nights
bullettemperature inversions are likely in this system
bulletthere is little or no wind in the center of the high
bulletLow pressure
bulletcloudy and cold
bulletprecipitation usually accompanies the passing of the cold and warm fronts





Last modified: January 27, 2005