Thermobaric cloud
Thermobaric clouds are a hazardous type of gaseous formation which can be extremely dangerous to starship navigation.

The region of space known as "the Delphic Expanse" was surrounded by a thick layer of thermobaric clouds which made it extremely difficult for ships to enter and exit, and took at least six hours to traverse at sublight velocities. In 2153, the Vulcan starship Seleya attempted to chart the thermobaric perimeter of the Expanse. After several days, they encountered a subspace eddy and were pulled inside. Later that year, the Earth starship  penetrated the perimeter in their mission to enter the Expanse and locate the Xindi, a species which had launched a devastating attack on Earth. While traversing the clouds, Enterprise came under attack by three , under the command of Duras, son of Toral, who was attempting to apprehend Captain Archer. In an effort to elude the Klingons, Archer ordered Enterprises speed increased to full impulse, despite the fact that the ship's intake manifolds were experiencing difficulty in processing the gases. In addition, the thermobaric clouds prevented the Klingons from acquiring a precise weapons lock on Enterprise, necessitating a reduction in the distance between the ships. Eventually, two of the Birds-of-Prey retreated, their crews fearful of entering the Expanse, and Archer and his crew were able to destroy the last attacking vessel, immediately before gaining access to the Expanse. ()

The thermobaric clouds surrounding the Delphic Expanse were dissipated in 2154, upon the destruction of the Sphere network which was responsible for the unusual properties of that area of space. ()

de:Thermobarische Wolke
nl:Thermobarische wolk
ru:Термобарические облака
Delphic Expanse
Celestial objects