Fig. 2. 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.