Morning Glory Cloud
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The Morning Glory cloud is a rare meteorological phenomenon consisting of a low-level atmospheric solitary wave and associated cloud, occasionally observed in different locations around the world. The wave often occurs as an
amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
-ordered series of waves forming bands of roll clouds. The southern part of the
Gulf of Carpentaria The Gulf of Carpentaria is a sea off the northern coast of Australia. It is enclosed on three sides by northern Australia and bounded on the north by the eastern Arafura Sea, which separates Australia and New Guinea. The northern boundary ...
in
Northern Australia The unofficial geographic term Northern Australia includes those parts of Queensland and Western Australia north of latitude 26th parallel south, 26° and all of the Northern Territory. Those local government areas of Western Australia and Q ...
is the only known location where it can be predicted and observed regularly due to the configuration of land and sea in the area.


Description

Morning Glory clouds can be observed from Burketown from late September to early November. The town attracts
glider pilots Glider or Gliders may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport ...
intent on riding this phenomenon. There are generally only a handful of well formed spectacular clouds during this period at Burketown. During the 2012 season there were only four to be seen from there, but quite a few ragged unspectacular cloud lines were seen. Often they start to break up before arriving at Burketown or pass to the north and only stay well formed over water. In an aircraft there is a significantly better chance of sighting the cloud. A Morning Glory cloud is a roll cloud, or arcus cloud, that can be up to long, high, often only above the ground. The cloud often travels at the rate of 10 to 20 metres per second. Sometimes there is only one cloud, sometimes there are up to ten consecutive roll clouds. Three distinct types of Morning Glory clouds have been identified. The Morning Glory is often accompanied by sudden wind squalls, intense low-level
wind shear Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical ...
, a rapid increase in the vertical displacement of air parcels, and a sharp pressure jump at the surface. Cloud is continuously formed at the leading edge while being eroded at the trailing edge. Showers or thunderstorms may develop in its wake. In the front of the cloud, there is strong vertical motion that transports air up through the cloud and creates the rolling appearance, while the air in the middle and rear of the cloud becomes turbulent and sinks. The cloud quickly dissipates over land where the air is drier. The cloud can also be described as a solitary wave or a
soliton In mathematics and physics, a soliton is a nonlinear, self-reinforcing, localized wave packet that is , in that it preserves its shape while propagating freely, at constant velocity, and recovers it even after collisions with other such local ...
or an
undular bore In meteorology, an undular bore is a wave disturbance in the Earth's atmosphere and can be seen through unique cloud formations. They normally occur within an area of the atmosphere which is stable in the low levels after an outflow boundary or ...
, which is a wave that has a single crest and moves without changing speed or shape. They have been called "the biggest waves on the planet". The wave may occur without the appearance of any clouds.


History of exploration

Unusual cloud formations have been noticed here since ancient times. The local Garrwa Aboriginal people called it ''kangólgi''.
Royal Australian Air Force The Royal Australian Air Force (RAAF) is the principal Air force, aerial warfare force of Australia, a part of the Australian Defence Force (ADF) along with the Royal Australian Navy and the Australian Army. Constitutionally the Governor-Gener ...
pilots first reported this phenomenon in 1942. The Morning Glory cloud of the Gulf of Carpentaria has been studied by multiple teams of scientists since the early 1970s. The first studies were published by Reg H. Clarke (
University of Melbourne The University of Melbourne (colloquially known as Melbourne University) is a public university, public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in the state ...
). Multiple studies have followed since then, proposing diverse mathematical models explaining the complex movements of air masses in the region.


Atmospheric conditions

One of the main contributors for the formation of the morning glory clouds is the mesoscale circulations associated with a difference in sea breezes that develop over the Peninsula and the Gulf. On the large scale, Morning Glories are usually associated with frontal systems crossing central Australia and high pressure in northern Australia. Locals have noted that the Morning Glory is likely to occur when the
humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...
in the area is high, which provides moisture for the cloud to form, and when strong sea breezes have blown the preceding day. The following is a summary of the conditions that cause the Morning Glory cloud to form in the Gulf of Carpentaria (after hypothesis of R.H.Clarke, as described in 1981). First, Cape York, which is the peninsula that lies to the east of the gulf, is large enough that sea breezes develop on both sides. 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, 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. There are other ways in which Morning Glory clouds form, especially in rarer cases in other parts of the world, but these are far less understood. Local weather lore in the area suggests that when the fridges frost over and the café tables' corners curl upwards at the Burketown Pub, there is enough moisture in the air for the clouds to form. Reportedly, all winds cease at ground level as the cloud passes over.


Other reported occurrences

Although the Morning Glory clouds over the southern part of the Gulf of Carpentaria are the most frequent and predictable, similar phenomena have occasionally been observed elsewhere, ''e.g.'', over central
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, in the
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,
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,
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, eastern
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, and other maritime regions of Australia. There was one distinct and well formed roll cloud observed spanning from horizon to horizon (east to west), just prior to midnight on 22 October 2015 at 50.3044°N, 96.9692°W (about 35 km North of
Winnipeg Winnipeg () is the capital and largest city of the Provinces and territories of Canada, Canadian province of Manitoba. It is centred on the confluence of the Red River of the North, Red and Assiniboine River, Assiniboine rivers. , Winnipeg h ...
,
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,
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), followed up by a series of them (but much less distinctive) shortly after midnight on 24 October 2015. There was another rare roll cloud formation that was observed in Masury, Ohio, 41.211168°N, -80.537849°W, on 27 May 2012, at 2:30 pm EST. This rare cloud event was observed by a mother and daughter, who also reported that high winds accompanied this formation, immediately after it being observed. Considering the rarity of the event in this region, it is seen as a once in a lifetime occurrence. Morning Glory clouds have occasionally been reported on Cape Cod and in the
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off the Mexican coast. The phenomenon has also been observed from
Sable Island Sable Island (, literally "island of sand") is a small, remote island off the coast of Nova Scotia, Canada. Sable Island is located in the North Atlantic Ocean, about southeast of Halifax, Nova Scotia, Halifax, and about southeast of the clo ...
, 180 km southeast of
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. A Morning Glory also passed through
Yarmouth, Nova Scotia Yarmouth is a port town located on the Bay of Fundy in southwestern Nova Scotia, Canada. Yarmouth is the shire town of Yarmouth County, Nova Scotia, Yarmouth County and is the largest population centre in the region. History Originally inhab ...
, in April 2009, as well as several communities in Newfoundland in May 2022. In contrast to the Gulf of Carpentaria where the Morning Glory is visible in the morning, those in the Maritimes have all occurred during the evening. Rare examples have been observed via satellite observation over the Joseph Bonaparte Gulf in the Eastern
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region of Australia as well as over the
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. A Morning Glory cloud was observed in 2007 over the
Campos dos Goytacazes Campos dos Goytacazes () is a city located in the northern region of Rio de Janeiro State, Brazil, with a population of 483,540 inhabitants. It is the largest city in Rio de Janeiro (state) outside of the Greater Rio de Janeiro metropolitan ar ...
bay in the state of Rio de Janeiro, Brazil. In August 2011, it happened again over Peregrino Field in South
Campos Basin The Campos Basin is one of 12 coastal sedimentary basins of Brazil. It spans both onshore and offshore parts of the South Atlantic with the onshore part located near Rio de Janeiro. The basin originated in Neocomian stage of the Cretaceous peri ...
in Brazil. The phenomenon was also recorded on Batroun's shore (Lebanon – Middle East) in September 2004. On 20 November 2013, a Morning Glory formation formed over the greater
Durban Durban ( ; , from meaning "bay, lagoon") is the third-most populous city in South Africa, after Johannesburg and Cape Town, and the largest city in the Provinces of South Africa, province of KwaZulu-Natal. Situated on the east coast of South ...
area. On 4 June 2015 a Morning Glory cloud formed over St. Cloud, FL, US. On 3 November 2016 a Morning Glory cloud formed over Appelscha, The Netherlands. On 5 February 2018 a Morning Glory cloud formed over
Richmond, Virginia Richmond ( ) is the List of capitals in the United States, capital city of the Commonwealth (U.S. state), U.S. commonwealth of Virginia. Incorporated in 1742, Richmond has been an independent city (United States), independent city since 1871. ...
, US. On 30 August 2018, a Morning Glory cloud formed over Ruskin, FL, US.


See also

*
Gravity wave In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the oc ...
*
Hector (cloud) Hector is a cumulonimbus thundercloud cluster that forms regularly nearly every afternoon on the Tiwi Islands in the Northern Territory of Australia, from approximately September to March each year. Hector, or sometimes Hector the Convector, is ...


Notes


External links

* Smith, Deborah. (2002
Morning Glory lures scientists to ride cloud nine
The Sydney Morning Herald. 16 September 2002
Meteorology of the Morning Glory Cloud

Morning Glory Cloud of the Gulf of Carpentaria
Galleries and articles covering the history of soaring the wave. {{DEFAULTSORT:Morning Glory Cloud Gulf of Carpentaria Cloud types Natural history of Nova Scotia North West Queensland