I thought about this as I was driving into work Thursday afternoon and was looking up at the sky and noticed an increase in cirrus clouds. Cirrus clouds are the wispy looking clouds that appear very high in the sky - roughly at or above 20,000ft. Because they form so high in the atmosphere they are made up of ice crystals (because the air up there is well below freezing). But did you know that cirrus clouds usually indicate warmer weather and a weather pattern change?
A good rule of thumb is that cirrus clouds indicate an impending storm system. And since storm systems, low pressure systems, have air that flows around the center of the low in a counter-clockwise fashion we warm up ahead of the low and cool down once it passes. Ahead of a warm front, especially in the fall, winter and spring seasons, cirrus clouds will appear as the warm air is gradually and slowly lifted up, condenses and freezes. As the warm front gets closer the cirrus clouds will begin to thicken up and become cirrostratus clouds, the milky white looking cloud. It's usually with this type of cloud a halo either around the sun or moon will appear.
The sky will continue to thicken and darken with clouds as they lower throughout the atmosphere and it will eventually begin to rain. A good indicator that rain is roughly 12 to 24 hours away are cirrus clouds.
Ahead of a cold front, air is forced upwards faster than ahead of a warm front. This quick rising of the air allow cumulonimbus (thunderstorm clouds) to develop. Following the passage of the low, stratus clouds (low level clouds) are typically found. These, too, can produce rain and give us the dreary and gray looking afternoons. So the next time you look up to the sky and see those thin, wispy cirrus clouds you know that changes to the weather will soon follow!
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