A Reformulation of Tropical Cyclone Potential Intensity Theory Incorporating Energy Production along a Radial Trajectory

Abstract

Abstract A modified formula for calculating tropical cyclone (TC) potential intensity (PI) from a balance between energy production and frictional dissipation in the TC surface layer is developed. This modified formula accounts for energy production and frictional dissipation at multiple radii (and therefore at multiple wind speeds) along the TC inflow trajectory. The PI maximum wind speed values V MAX are calculated using this expanded formula for four canonical radial profiles of wind speed. These results are compared to PI V MAX values calculated using the standard assumption that all energy production and frictional dissipation relevant to maximum intensity occurs at the radius of maximum winds (RMW). The new PI formulation developed here results in PI V MAX values substantially higher than the standard PI V MAX for all four of the radial wind speed profiles examined; the difference is explained by the increase in the outer radial limit of energy production. This increase holds true even if outflow temperature increases with increasing radius, although the V MAX increases with increasing outer radius are somewhat more modest in this case. The extended PI formula yields V MAX values 3–17 m s −1 higher than the standard PI V MAX value when calculated with outer energy production–dissipation limits of 2.0–2.5 RMW, although it yields potentially unrealistic values when calculated with larger outer limits (e.g., 6 RMW). These results are presented as a potential explanation for why individual TCs can exceed their standard PI V MAX values in terms of the storm thermodynamics.