According to classical ideas, cold fronts typically are divided into two main sub-types: Ana and Kata type cold fronts. Real examples of Cold Fronts do not always show these model characteristics, but nevertheless the main characteristics can briefly be summarised as follows:
According to classical ideas cold air moves rapidly against warm air, thereby creating convergence at the surface line between the two airmasses. This convergence forces the warm, moist air to ascend on the frontal surface. The cloud band develops, inclined rearward from the surface cold front. Consequently, in this case the main zone of cloudiness and precipitation appear behind the surface front. the surface front passage may be accompanied by intensive line of convection due to the forced ascent, but at the rear of the surface front the precipiation is more stratiform type. This is called an Ana cold front.
In Kata Cold front, the ascending air ahead of the cold front is overrun by dry air being advected from the rear of the cold front. The dry air originates from upper levels of the troposphere or even from the lower levels of the stratosphere, and it crosses the Cold Front from behind. Due to this process, Therefore, frontal clouds and precipitation tend to lie ahead of the surface front. The dry air overrunning moist air below leads to a formation of a potentially unstable layer close to the leading edge of the frontal cloud band. As a result of ascent, this area is suitable for the development of pronounced instability which is often observed as convective precipitation, thunder, etc. rather than stratiform type of precipitation.
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Ana-type Cold front | Kata-type Cold front |
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