How are 'Morning Glory' clouds maintained?
These are some of the most recent areal photographs taken of this phenomenon. The Morning Glory clouds are the visible manifestation of atmospheric Internal Solitary Waves (see the schematic in (b) below). They propagate on a sharp interface between a relatively dry layer ambient air above and a layer of sea water laden air pushed in from the night before below. When the moist air rises the cloud is formed above the condensation level and eventually evaporates at the trailing edge of the wave.

In these photographs, the cloud itself appears as a cylindrical shaped core with high vorticity at a height of $500$ m and a $1$ km diameter. They may stretch for thousands of kms while traveling at up to $50$ km/h.

Internal Solitary Waves are stable by definition, they are waves of permanent form which owe their existence due to a balance between nonlinear wave-steepening and linear wave dispersion. Of course in the environment there are several other nonlinearities which could potentially break apart this structure through various mechanisms. However, devoid of other atmospheric forcing these waves can travel thousands of KMs without loosing much energy.

A final point is that these waves are ubiquitous but the thing is that we very rarely can observe them is such glorious ways, so there is nothing that says that the Morning Glory is special as far as stability goes compared to other locations on Earth. It is in fact common for such disturbances to maintain their shape over large distances.







Source: Ouazzani, Zaim R., et al. "The Morning Glory: Flow visualization by Mother Nature." Physics of Fluids (1994-present) 26.9 (2014): 091110.