This is a new sky phenomenon people are calling chem bombs. You can watch it creep up slow from the horizon, then cover the entire sky. These were all taken over New Orleans. Often, you’ll see clouds appear to be shooting out from the edges of these things, and you’ll see triangle or “V” patterned trails. They also appear to come in very high above any other clouds, and they have a fuzzy, fibrous appearance. You can search for them on radar, and usually you can watch them bloom from a moving pin-point location. The prevailing thought is that the chemicals are dumped from large fire-fighting planes that are equipped to dump large amounts of water, or in this case “aerosols,” from high in the atmosphere.
NOLA Skies 