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

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.

The Variability and Predictability of Axisymmetric Hurricanes in Statistical Equilibrium

“…While this process may be initiated by asymmetric disturbances, it is unclear whether such variability requires asymmetries. Here we explore variability associated with only the symmetric circulation, which provides a basis for comparison to three-dimensional studies that include asymmetries (Brown and Hakim 2013).…”

“…Nolan et al (2007) use RCE to examine the sensitivity of tropical cyclogenesis to environmental parameters, and also find the spontaneous development of tropical cyclones. The current paper uses RCE of a specific state, a mature tropical cyclone, to examine the variability and predictability of these storms in an axisymmetric framework; results for three-dimensional simulations are presented in Brown and Hakim (2013).…”

Predictability of Tropical Cyclone Intensity Evaluated through 5-yr Forecasts with a Convection-Permitting Regional-Scale Model in the Atlantic Basin

“…5d; significant after 12 h), which might be in part due to the difficulty in forecasting rapid intensity changes. Given the absolute error remains the primary verification metrics in various studies (e.g., Elsberry et al 2007;Bhatia and Nolan 2013) and operational centers including the NHC, the mean absolute errors were used in the remainder of this study to make it more comparable to other studies.…”

“…Using similar initial perturbations but with the inclusion of environmental vertical wind shear, Zhang and Tao (2013) found that larger magnitudes of shear decrease the intrinsic predictability of the TC, especially during periods of genesis or rapid intensification (RI). Furthermore, Hakim (2013) and Brown and Hakim (2013) explored the possible time scale of intrinsic predictability of several TC characters under an idealized equilibrium framework and found that most features near eyewall region maintained their predictability for no longer than 48 h without considering the ambient environment. It is noteworthy that most studies on TC intensity predictability focused on intrinsic predictability of single or idealized cases.…”

“…With all these statistical models demonstrating various factors that may affect TC intensity, it is worth exploring whether these factors, such as wind shear, moisture, and translation speed, might also impact intensity forecast errors. Most recently, Bhatia and Nolan (2013) examined statistically the uncertainties of TC intensity forecasts with respect to the synoptic environment conditions. They focused on the forecast uncertainty in the NHC's operational forecast guidance models (both statistical and dynamical) as well as in the NHC official forecasts.…”