Variability and Predictability of a Three-Dimensional Hurricane in Statistical Equilibrium

Abstract

Abstract The internal variability and predictability of idealized three-dimensional hurricanes is investigated using 100-day-long, statistically steady simulations in a compressible, nonhydrostatic, cloud-resolving model. The equilibrium solution is free of the confounding effects of initial conditions and environmental variability in order to isolate the “intrinsic” characteristics of the hurricane. The variance of the axisymmetric tangential velocity is dominated by two patterns: one characterized by a radial shift of the maximum wind, and the other by intensity modulation at the radius of maximum wind. These patterns are associated with convectively coupled bands of anomalous wind speed that propagate inward from large radii with a period of roughly 5 days, the strongest of which is associated with an eyewall replacement cycle. The asymmetric tangential wind is strongest radially inward of the radius of maximum wind. On average, asymmetries decelerate the azimuthal-mean tangential wind at the radius of maximum wind and accelerate it along the inner edge of eyewall. Predictability of axisymmetric storm structure is measured through the autocorrelation e-folding time and linear inverse modeling. Results from both methods reveal an intrinsic predictability time scale of about 2 days. The predictability and variability of the axisymmetric storm structure are consistent with recently obtained results from idealized axisymmetric hurricane modeling.