 This upper bound is called the "maximum potential intensity", formula_7, and is given by

where formula_9 is the temperature of the sea surface, formula_10 is the temperature of the outflow ([K]), formula_11 is the enthalpy difference between the surface and the overlying air ([J/kg]), and formula_12 and formula_13 are the surface exchange coefficients (dimensionless) of enthalpy and momentum, respectively.The surface-air enthalpy difference is taken as formula_14, where formula_15 is the saturation enthalpy of air at sea surface temperature and sea-level pressure and formula_16 is the enthalpy of boundary layer air overlying the surface.The maximum potential intensity is predominantly a function of the background environment alone (i.e.