Tropical cyclone flow asymmetries induced by a uniform flow revisited

Download
Author
Thomsen, Gerald L.
Smith, Roger K.
Montgomery, Michael T.
Date
2015-08-25Metadata
Show full item recordAbstract
We investigate the hypothesized effects of a uniform flow on the structural evolution of a tropical cyclone using a simple idealized, three-dimensional, convection-permitting, numerical model. The study addresses three outstanding basic questions concerning the effects of moist convection on the azimuthal flow asymmetries and provides a bridge between the problem of tropical cyclone intensification in a quiescent environment and that in the vertical shear over a deep tropospheric layer. At any instant of time, explicit deep convection in the model generates flow asymmetries that ten to mask the induced flow asymmetries predicted by the dry, slab boundary layer of Shapiro, whose results are frequently invoked as a benchmark for characterizing the boundary layer-induced vertical motion for a translating storm. In sets of ensemble experiment in which the initial low-level moisture field is randomly perturbed, time-averaged ensemble mean fields in the mature stage show a coherent asymmetry in the vertical motion rising into the eyewall and in the total (horizontal) wind speed just above the boundary layer. The maximum ascent occurs about 45 degrees to the left of the vortex motion vector, broadly in support of Shapiro's results, in which it occurs ahead of the storm, and consistent with one earlier more complex numerical calculation by Frank and Ritchie. The total wind asymmetry just above the boundary layer has a maximum in the forward right sector, which is in contrast to the structure effectively prescribed by Shapiro based on an inviscid dry symmetric vortex translating in a uniform flow where, in an Earth-relative frame, the maximum in on the right.
Description
The article of record as published may be found at: http://dx.doi.org10.1002/2015MS000477
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.Collections
Related items
Showing items related by title, author, creator and subject.
-
Effects of uniform target density on random search
McNish, Michael J. (1987-09);This thesis was motivated by a study performed by Commander Submarine Force Pacific (COMSUBAC) of detection rates for a random search model. COMSUBPAC's study included that the probability of nondetection to time t, ... -
Sensitivity of tropical-cyclone models to the surface drag coefficient in different boundary-later schemes
Smith, Roger K.; Montgomery, Michael T.; Thomsen, Gerald L. (Royal Meteorological Society, 2014-04);The recent study of the sensitivity of tropical-cyclone intensification to the surface drag coefficient in a three-dimensional model by Montgomery et al. is extended to include a wind-speed-dependent drag coefficient and ... -
Variability in hurricane boundary layer characteristics observed in a long-term NOAA dropsonde archive
Wendt, Robert D. T. (Monterey, California. Naval Postgraduate School, 2014-06);The statistical properties of five boundary layer height definitions were examined in 6,593 NCAR GPS dropsonde observations of the hurricane environment. Based on similar composite analysis studies, these boundary layer ...