Portal storm



The Portal Storm is the swirling mass of clouds that can be observed directly above The Artifact, outside Mombasa in the levels and  in Halo 3.

Appearances
The Storm was first seen in the Halo 3 Announcement Trailer. When the camera shows the artifact being uncovered and activated, the storm lies directly over it. Lightning bolts are seen flashing out of the clouds. The formation seems to have an eye, like a hurricane would. When the portal is activated, the beam travels up through this eye and disappears.

In Halo 3, in the level, when a player looks up at some of the computer monitors, you will see a map of the local area. The map will have a mass of clouds beginning to show a swirling motion around the area. When you enter the level Tsavo Highway, you can see a doughnut-shaped mass of clouds above the artifact that the Covenant are digging up. When you proceed to the level The Storm, which is named after (presumably) the storm above the portal, the storm has intensified and grown. The clouds now bring rain to the area, and certain parts of the cloud glow as if cloud-to-cloud lightning is occurring. At a point in the level, a group of UNSC Marines are present around a radio. Intel comes over the communications channel and says "...winds inside the storm have been clocked at over 200 kilometers per hour." When the Prophet of Truth activates the Portal, the solid blue beam shoots up into the cloud formation's eye and opens the portal to the Ark.

After the portal is opened, and the level Floodgate begins, the remains of the clouds are seen broken up and swirling around the portal in the sky, having been disrupted by the opening of the portal itself.

Artificial or Natural?
The Storm above the portal may be an artificial storm, created only by the activation of the Ark Portal. As the Forerunners could manipulate weather on the Halo installations, it would not be impossible for them to create a storm on Earth. However, the storm could just be the portal's influence in the upper level atmosphere; it is unlikely to be a hurricane because a hurricane's eye neither rotates that fast nor stays in one place.

Trivia

 * There is also a weather phenomena in Half-Life 2 and its episodes referred to as "Portal Storms".