This photograph taken over Namibia reveals another effect of jet streams. Turbulence along the margins of the jet stream may explain the sharp boundary. The point of convergence of the two air streams is precisely located by this photograph. Shadows mark the cloud edges against a sunlit Namibian backdrop. These cloud streets over the reefs of the Maldive Islands in the Indian Ocean denote the prevailing wind direction, the cloud streets lying parallel with the wind.
Turbulent air lifted by the windward portions of the islands promotes cloud formation downwind.
The combination of warm water temperature and hundreds of square miles of ocean, uninterrupted by land masses, results in a regular cumulus and stratocumulus cloud formation. In the Pacific Ocean the Trade Winds propel the clouds from east to west across the ocean. In addition to illustrating how gracefully the clouds circumnavigate Hawaii's volcanic peaks, the photograph shows how the prevailing wind direction dictates that the north and northeast of the island are wetter than the western side of the island and frequently under cloud. Shuttle astronauts have frequently observed Dek Island in Lake Tana in Ethiopia, the source of the Blue Nile, with a well-developed cloud tail. This occurs when the land mass disrupts the air flow, creating downwind turbulence that promotes condensation.