Entropic Balance Theory and Radar Observation for Prospective Tornado Data Assimilation - Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications - page 439

Fig. 18.12 Barotropic case
of the entropic balance
expressed in the right hand
rule

The wrap-around mechanism developed on the basis of the entropic
balance theory provides the flow velocity ( 18.5 ), which explicitly includes the
thermodynamic terms of entropy S varied by heating d'Q, and the Lagrange
multipliers

of the constraints of density and entropy, respectively. The wrap-
around mechanism and the entropic balance theory seem to explain the transition
from supercell to tornado. Also, the wrap-around mechanism, together with the
kinematic lower boundary condition, better explain the important findings that all
observed tornadoes contact the ground perpendicularly, contrary to the expectation
from the upward tilting of a horizontal vortex tube.

˛ and ˇ

18.8 Schematic Entropic Balance Model of Supercell

and Tornadogenesis

Figure 18.4 illustrates schematically the entropic balance model of supercell and tor-
nadogenesis under meandering westeries. When a large-amplitude trough develops,
more water vapor evaporated from Gulf Stream is transported by the southerly flow
deeper inland into the central US Great Plains and meets with the dry air transported
by the north-westerly jet-stream. In a developing supercell, the moisture of the
southerly flow condenses and releases latent heat into the surrounding air, resulting
in an entropy increase (18.26b) that is shown by circled plus sign, called an entropic
source, in the figure. The hydrometeors such as raindrops and ice crystals created
by the condensation and freezing are lifted by the updraft, reaching near the cloud