Can Contrails from Jetliners Indicate a Change in the Weather?
Contrails can actually indicate that a change in the weather is on its way, especially during the cooler months of the year. How? Well, letís say that the weather is cold and dry and there is a deep blue sky. A polar or arctic air mass moved into your area recently and you begin to notice the contrails from passing aircraft. This is a sign that the upper levels of the atmosphere have started to moisten up a bit to allow for the contrail to persist for an extended period. What this means is that warmer air will soon return and/or precipitation is on its way. Since warm, moist air is much lighter than cold dry air, it rises above the cooler denser air. Therefore, the upper atmosphere is first affected by the approaching warm, moist air. This additional moisture content in the air in the upper atmosphere causes the contrail to last several minutes and sometimes the sky can be crisscrossed by numerous contrails. Many times, a general increase of high cloudiness begins after the first contrails are visible. Cirrus clouds are usually the first on the scene. Then, the cloud cover lowers and thickens and precipitation develops. Other times, contrails signify that warmer weather is on its way with no precipitation.