Here's why:
Fair weather:
* High altitude: Cirrus clouds form at very high altitudes (above 20,000 feet), where the air is very dry and cold. This means they are unlikely to produce precipitation.
* Stable atmosphere: The presence of cirrus clouds often indicates a stable atmosphere, which means there is little vertical air movement and therefore less chance of storms developing.
Approaching bad weather:
* Precursors to storms: While cirrus clouds themselves are harmless, they can be a sign that a storm system is approaching. As warm air rises and cools, it can form cirrus clouds that spread out ahead of the storm front.
* Changes in appearance: Cirrus clouds that thicken, become lower, or appear in larger numbers can signal an approaching storm. If they start to take on a "mackerel sky" pattern (small, wavy clouds) or develop into cirrostratus (thin, sheet-like clouds), it's a good indicator of impending rain or snow.
In summary:
Cirrus clouds are a bit of a double-edged sword. While they often signify fair weather, they can also be a sign of changes in the atmosphere that could bring about precipitation or storms. If you see cirrus clouds starting to thicken or change shape, it's a good idea to keep an eye on the weather forecast.
