The Gulf of Carpentaria, Queensland, Australia is home to one of the world's most extraordinary meteorological phenomenon. From late September to early November, before the start of the rainy season, the sky above Burketown in far North Queensland's Gulf of Carpentaria, develops strange rolls of clouds called Morning Glory. These clouds, that form in a series of bands, can be up to 1,000 km long and 2 km tall and often form only 100 to 200 meters above the ground, attracting hang glider pilots who ride over it just as a surfboard rider does on the ocean.
Morning Glory clouds are often accompanied by dangerous turbulence such as sudden wind squalls, intense low-level wind shear, rapid increase in the vertical displacement of air parcels, and sharp pressure jump at the surface. In the front of the cloud there is strong vertical upward motion of the air, while the air behind the cloud sinks creating a rolling effect. The clouds can achieve an airspeed of 60 kilometers per hour over a surface with little discernible wind. Showers or thunderstorms may also develop in its wake.
What causes Morning Glory cloud is not clearly understood, but the particular configuration of the land and sea on the Cape York Peninsula is believed to play a significant part in its formation.
The peninsula tapers off from about 350 miles wide to 60 miles as it extends north between the Gulf of Carpentaria to the west and the Coral Sea to the east. During the day, the breeze from the Coral Sea coast blows in from the east and the breeze from the gulf blows in from the west. The two breezes meet in the middle of the peninsula in the evening, forcing the air to rise there and form a line of clouds over the spine of the peninsula. When night comes, the air cools and descends and at the same time a surface inversion (where air temperature increases with height) forms over the gulf. The densities in this stable layer are different above and below the inversion. The air descending from the peninsula to the east goes underneath the inversion layer and this generates a series of waves or rolling cylinders which travel across the gulf. These cylinders of air roll along the underside of the inversion layer, so that the air rises at the front of the wave and sinks at the rear. In the early morning, the air is saturated enough so that the rising air in the front produces a cloud, which forms the leading edge of the cylinder, and evaporates in the back, hence forming the Morning Glory cloud. The cloud lasts until the surface inversion disappears with the heating of the day.
Morning Glory clouds have occasionally been observed elsewhere such as central United States, the English Channel, Munich, Berlin, eastern Russia, and other maritime regions of Australia. But the Gulf of Carpentaria is the only known location where it can be predicted and observed on a more or less regular basis.
This article has been revised and republished from an earlier article that appeared on Amusing Planet on June 11, 2010
Subscribe to our Newsletter and get articles like this delieverd straight to your inbox