A front in a meteorological sense is the zone of contact between air masses with different density, temperature and humidity. The frontal band is the area in which two air masses come into direct contact, the area in which energy exchanges take place and where the more intense atmospheric phenomena are produced. Generally, a front appears as a more or less regular surface, with a low angle , slightly inclined, and it generally forms a curved line on the horizontal plane. Meteorologists identify three types of fronts: cold, hot and occluded.
When hot or cold fronts form, the condensation processes free thermal energy and this contributes to creating areas at different temperatures, triggering off local circulation and mixing and contributing to a further increase in the instability of the air masses.
The front of a perturbation, in the initial phases of its formation, is generally related to the so-called wind front, that is associated to the progress of cold masses of air that descend from the perturbation. At times the wind front is made visible by dust clouds that rise from the ground (as in dust storms) or by the condensation front that gives rise to the formation of spectacular arc-shaped clouds on the same level of the perturbation front.
The presence of mountains along the course of the front can bring about variations and deformations of various kinds that can make the perturbation evolve in an unpredictable way.

Special reports

From the Multimedia section