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What are Weather Fronts?
Fronts are the boundary between two air masses having different type of atmospheric characteristics like temperature and humidity. This boundary or a transition zone between different air masses exists due to the movement of an air mass towards another air mass, having different properties than its own and is called the Frontal Surface. When this Frontal Surface touches the ground, we call it a Front or a Weather Front. The Frontal Surface may extend for hundreds of miles horizontally, and may ascend upwards of the surface of the earth to great heights; the height and width of the Frontal Surface is known as the Frontal Zone.
Types of Fronts
There are many different types of Fronts; the basic classification of the Fronts is done based on the prevalent meteorological conditions of the air masses concerned. Different weather conditions exist on the opposing sides of the Fronts; since cold air is heavier and denser than warm air, a Front attains a sloping shape with warm air gently sloping above the cold mass of air. The main types of the Fronts are:
- Warm Fronts
Warm Fronts are Fronts where the cold air is being replaced by the warm air. The dense heavy cold air forces the approaching warm air to ascend in a sloping manner. The rising warm air cools rapidly and condenses into clouds. When the rapidly cooling warm air is full of moisture content, dense clouds form in the Frontal Zone; rain and thunderstorms follow soon due to the available precipitation. However, when the warm air mass is dry, scattered clouds form and little or no rains occur. Cirrus clouds appear at the onset of a Warm Front, replaced by Cirrostratus clouds later on; however, precipitation starts to fall only after Altostratus clouds are formed and that too may not reach the surface and dissipate as Virga. Nevertheless, with the approach of Nimbostratus clouds the rains really start to pour down heavily. The overall movement of a Warm Air Front is slow; therefore, a weather brought through a Warm Front can linger for several days in a go.
- Cold Fronts
Cold Fronts are Fronts where the cold air replaces the warm air. As a Cold Front moves faster than a Warm Air Front, it tends to sink under the warm air mass due to its heavier density. This forces the warm air to rise above the cold air quite rapidly, and loose its heat due to this sudden elevation. Very soon, this rising column of air reaches a suitable temperature and Dew Point where the moisture that it contains start to condense into water droplets; huge columns of vertically developed Cumulus clouds known as the Towering Cumulus form through the rapid condensation of moisture laden warm mass of air. Cumulonimbus clouds also form in such conditions, and thunderstorms occur whenever the warm mass of air is rich in moisture. The weather brought by Cold Fronts is abrupt and happens very swiftly, and is marked by sudden changes and extreme conditions.
- Occluded Fronts
Occluded Fronts are the Fronts where the Cold Fronts overrun the Warm Air Fronts. A mix of different weather properties exist in Occluded Fronts; cold occlusion ahead and a warm air mass at the tail. When two cold air masses move to replace a warm air mass from opposing sides, the warm air rises between them; this rising warm air cools down and the moisture it contains condenses into clouds. Rains and snow may fall, depending on the amount of humidity contained by the warm mass of air. Occluded Fronts may contain combinations of weather conditions having properties of both the Cold Front ahead, and the Warm Front in the rear of the Frontal movement.
- Stationary Fronts
Stationary Fronts are Fronts where virtually no significant movement takes place between the approaching air masses; there are four almost permanent stationary Fronts on Earth at the Arctic, Polar, Mediterranean, and the Inter-Tropical regions. A condition of a Stationary Front occurs where two Fronts meet but neither has the strength to displace the other. Therefore, a sort of stalemate happens and both Fronts maintain their positions and properties against each other.
Importance of Fronts during Flying
It is very important for aviators to know about the Weather Fronts and their properties in detail. The knowledge of common locations and the weather associated with the different types of Fronts help plan the flights in a safer way. Recognition of the approaching Fronts through the types of clouds and other different weather parameters associated with them is very helpful in flying. Potentially dangerous and hazardous weather conditions like Squall Lines and intense thunderstorms can form due to Fronts. A Frontal passage is always an indicator of changing weather, therefore the more we know about Fronts the better it is.
Learn more about aviation weather with Weather Flying by Robert Buck. Regarded as the bible of weather flying, this aviation classic not only continues to make complex weather concepts understandable for even the least experienced of flyers, but has now been updated to cover new advances in technology.