Around noon on Wednesday, “contrails” showed up on the visible satellite imagery over the northeast part of the Gulf of Mexico. This is unique because contrails are not often seen on satellite imagery.
You may be asking, “what is a contrail?” According to the National Weather Service, “A contrail is the condensation trail that is left behind by a passing jet plane.”
Contrails form when hot humid air from jet exhaust mixes with the air around the plane that has low vapor pressure and a lower temperature. The mixing occurs directly behind the plane due to the turbulence generated by the planes engine.
The formation of contrails is very similar to what happens when you breath on a cold winter day and you can see your own breath in the form of a "cloud".
You may have noticed that on some days this "cloud" you produce lasts longer than on other days where it quickly disappears. The length of time that a contrail lasts is directly proportional to the amount of humidity that is already in the atmosphere. The drier the atmosphere the shorter lived the contrail, the more humidity in the atmosphere the longer the contrail will last.
If the atmosphere is too dry, contrails will not form. That is why you don’t always see contrails when planes fly overhead.
On occasion, especially if ascending or descending, a jet plane will pass through a much drier or more moist layer of atmosphere which may result in a broken pattern to the contrail, with it appearing in segments rather than in one continuous “cloud”.
If contrails persist for a long enough period of time they can spread out across the sky due to the prevailing winds at the level of the atmosphere where they formed.