Download What is a front? - OshEarthScience

Aim: What is a front?
•Fronts are boundaries that separate air masses of
different densities.
•One air mass is always warmer and often contains
more moisture than the other.
•Types of fronts
•Cold front
•Warm front
•Stationary front
•Occluded front
Understanding Fronts
– Fronts (Cold) A cold
front represents a
zone where cold,
dry, stable polar air
is replacing warm,
moist, conditionally
unstable
subtropical air.
Cold Front
– At the cold front, the
cold, dense air wedges
under the warm air,
forcing the warm air
upward.
– Behind the front the air
cools quickly (Freezing
level dips as it crosses
the front).
– Winds shift.
– Leading edge of the
front is steep. Vertical
rise to horizontal
distance is 1:50
Warm Front
A warm front is the opposite of a
cold front.
In this case, warm air displacing
cold air.
The front is drawn as a solid red line
with semicircles pointing in the
direction of the movement of the
warm front.
The direction of movement is
determined from the weather
conditions.
In this case the warm is less dense
than the air it is displacing so it
rides up over the top of the dome
of cold air.
This makes the ascent of the air
much slower compared to a cold
front
Warm Front
Understanding the Weather
• Fronts (Warm)
The occluded front
• Fronts
– Cold front is rapidly approaching the slower moving
warm front.
Understanding the Weather
• Fronts (Cold Occlusion)
• The cold front now overtakes the warm front.
Cold Occluded Front
• Fronts (Cold Occlusion)
• Cold front now under rides and lifts the warm
front and the warm air mass off the ground.
Warm Occluded Front
• Fronts (Warm Occlusion)
– When the cold front catches up to and overtakes
the warm front, the lighter air behind the cold front
is unable to lift the colder heavier air off the ground.