Document Type

Conference Paper

Publication Date






Conference Name

American Institute of Aeronautics and Astronautics Aviation 2019 Forum


In 1966, meteorologist R.S. Scorer attempted to explain how large-scale oceanic tropical depressions become hurricanes or typhoons. His model was based on the idea that when these large-scale tropical depression structures begin to rotate, mostly due to Coriolis effects, an annular outer portion of that structure changes suddenly to a potential vortex segment, with the same outer radial limit as the low-pressure structure, but with an inner radius that conserves the overall system angular momentum and kinetic energy. By analogy with the "jump" instability describing sudden buckling of a vertical column, this paper shows that his conjecture merits additional consideration. If valid, the Scorer model implies that the controlling large scale flow is essentially an inviscid Rankine vortex. While hurricanes can sustain this Rankine vortex "eye structure" over warm ocean, over land smaller-scale tornadoes and dust devils cannot draw from a similar sustaining energy source. Scorer's model implies that, without additional energy, the outer inviscid vortex region should force the rotating inner cylindrical region to collapse as the overall inviscid structure proceeds toward the rotational axis. That vortex evolution requires additional energy- from an unknown source.

This paper utilizes Scorer's finite vortex domain hypothesis on an evolving aircraft wake vortex pair, and his assertion that the inviscid vortex pair is the controlling flow, to generate turbulent non-equilibrium vortex cores and by extension explain how tornadoes and dust devils form from rotating atmosphere.


© 2019 by Robert L. Ash.

Included with the permission of the author.

Original Publication Citation

Ash, R. L. (2019). Wake vortex pair formation as an analog for dust devil and tornado genesis. Paper presented at the American Institute of Aeronautics and Astronautics Aviation 2019 Forum, Dallas, Texas, June 18, 2019.

Ash-2019-WakeVortexPairFormationPowerpoint.pdf (3208 kB)
Powerpoint Presentation at the AIAA Aviation 2019 Forum