Fronts
This page contains information reguarding frontal systems and the weather
they can bring with them.
Any place where air masses with different properties meet, a weather front exists.
The terms can be slightly misleading too: the terms are relative. A warm front
exists where 10 degree air meets 30 degree air but it's not warm by any measure
of the term. Cold air is more dense than warm air so anyplace where 2 dissimilar
air masses meet, the cold air stays near the surface and the warm air rises above
it.
Following are the different conditions you can expect with various types of fronts.
Cold Fronts
Visibility: There is good visibility behind the front because the warm air rises
rapidly and carries pollutants and various particulates with it.
Flight conditions: Bumpy because of the rising thermal currents.
Precipitation: Showers in the frontal area as the warm air is forced aloft and the
moisture condenses.
Cloud type: Cumulus, due to air being rapidly raised to it's condensation level
(see the page reguarding thunderstorms for more
info about thunderstorm formation.). Cumulus coulds are a sign of unstable air.
Icing
possibility: Clear ice due to the large droplets of water in cumulus clouds
which freeze into clear sheets of ice.
Warm Fronts
Visibility: Poor because pollutants are trapped near the surface due to warm air
aloft. When air is warmed at the surface, it can only rise until it reaches air at its own
temperature.
Flight conditions: Smooth because of the lack of any major thermal activity.
Precipitation: Drizzle or continuous rain as moist air is slowly raised to the
condensation level.
Cloud type: Stratus or layered as a result of slow cooling.
Icing
possibility: Rime ice because of the small water droplets in the air which
freeze instantaneously upon contacting an airplane and form a rough, milky coating.
Occluded Fronts
These occur when a fast moving cold front overtakes a warm front and lifts the warm air
away from the surface. Occluded fronts contain the worst features of both warm and cold
fronts: turbulent flying conditions, showers and/or continuous precipitation, poor visibility
and broad geographic extent.
Stationary Fronts
If air masses maintain their warm/cold identity but don't exert any displacement force, a
stationary front is formed. The associated weather with these fronts cover a large
geographic area.
When looking at a weather map showing frontal positions, cold fronts will be marked in
blue, warm fronts in red, occluded fronts in purple, and stationary fronts alternate red and
blue. Also, fronts can be identified on black-and-white charts because cold front symbols
look like icicles and warm front sybmols look like blisters. Occluded fronts show both
icicles and blisters on teh side of the front in the direction of movement, and stationary
fronts show the symbols on opposite sides of the frontal line.