Characteristics of the upper-tropospheric environmental flow around hurricanes

Abstract

A rotated coordinate composite of all hurricanes from a five-year period is used to study the general properties of the hurricane outflow layer. Coordinate rotation improves the representation of the outflow jet and the associated extrema of radial and tangential wind, but tends to obscure the geographically persistent features of the upper-tropospheric environment such as the midlatitude westerlies. The amplitude of the asymmetric radial wind is twice that of the symmetric, while the amplitudes of tangential winds are equivalent. A comparison of geographic and rotated coordinate composites indicates that both the outflow jet and the midlatitude westerlies are important structures for the import of angular momentum into the hurricane by horizontal eddy fluxes. -from Author