cold front - leading edge of cold air
DESCRIPTION
Fronts. front - an area between two colliding air masses. cold front - leading edge of cold air denoted with a line and filled blue triangles pointing in the direction of advance . warm front - leading edge of warm air - PowerPoint PPT PresentationTRANSCRIPT
cold front - leading edge of cold air
denoted with a line and filled blue triangles pointing in the direction of
advance warm front - leading edge of warm air
denoted with a line and filled red semicircles in the direction of advance
Frontsfront - an area between two colliding air
masses
Frontal Lifting
more dense DAR
MAR
lifting condensation level
Cumulonimbus clouds
less densecP is a continental polar
air mass - cold, dry, stablemT is a maritime tropical air mass - warm, humid,
unstable
An advancing cold front
note the steep nature of the front
this is a cP or mP air mass
cirrus clouds signal an
advancing front
air pressure and
temperature at the front line
fall dramatically
this is a mT air mass
heavy rain,
winds
note that cumuliform clouds
develop in this case
An advancing warm front
temperature inversion
often occurs
the active warm air mass slides
over the ‘wedge’ of passive cold
air
note that stratiform clouds develop in this
case
drizzly rain
cirrus clouds signal an
advancing frontnote the
progression of cloud
development
show animations
Polar Front, Jet Streams, and Rossby
Waves
the polar front is the area of contrast between cold polar air and warm subtropical air
Aleutian Low Icelandic Low
Midlatitude Cyclonesthese migrating storm systems have low
pressure cores, converging, ascending air, and they rotate counterclockwise in the NH
show animations
the polar jet stream follows the
edge of Rossby
waves - it meanders between 30-70° N
show animations
Mid-latitude Cyclones
• Also known as wave cyclones due to the undulating nature of frontal boundaries and course of the jet stream
• Form due to the collision of warm and cold air masses
• Different from tropical cyclones• High-speed jet stream winds guide
cyclones along their “tracks”
it takes about a week for this whole
process to occur
the initiation of a cyclone occurs when cold and warm air masses
collide - it requires surface convergence towards a low pressure
area and divergence aloft
eastward of the collision front, warm air moves northward and cold air
moves southward - the beginning of counterclockwise rotation - this
movement draws warm air from the south and cold air from the northcold front
warm front
will winds flowing into the low flow parallel to
the isobars?
A squall line can form when a fast-moving cold front
encounters warm air and violently uplifts it
these frontal clouds are 17,000 m (55,000 ft) high,
and extreme winds and rain are affecting the surface
during this stage of a cyclone’s life cycle, the faster-moving cold front
overtakes the warm front and wedges beneath it (”occluding” or
closing it)
precipitation is heavy to moderate at this
stage
during this stage, there is no more
uplifting of air and the storm gradually
fades
there is still some counterclockwise air flow with light winds
show animations
average cyclone storm tracks follow the sun’s movement in the sky
with the seasons
Good luck on the midterm!