Schematic illustration of the secondary flow around the eye
of a hurricane. The frictional indraft feeds the buoyancy-driven
primary updraft and outflow in the eyewall cloud. Saturated convective
downdrafts in the eyewall and the evaporatively driven descent along
the inner edge of the eyewall feed moist air into the volume below
the inversion surface. Dynamically driven descent of dry air inside
the eye warms the air column adiabatically. The descent is forced
as entrainment into the eyewall draws mass from the bottom of the
eye into the eyewall. Balance between moist-air production and
loss by entrainment determines the rate of rise or fall of the
inversion.