A cloud-resolving model is used to examine the virtually shear-free evolution of incipient tropical cyclones initialized with different degrees of misalignment between the lower- and middle-tropospheric centers of rotation. Increasing the initial displacement of rotational centers (the tilt) from a negligible value to several hundred kilometers extends the time scale of hurricane formation from 1 to 10 days. Hindered amplification of the maximum tangential velocity υm at the surface of a strongly perturbed system is related to an extended duration of misalignment resulting from incomplete early decay and subsequent transient growth of the tilt magnitude. The prolonged misalignment coincides with a prolonged period of asymmetric convection peaked far from the surface center of the vortex. A Sawyer–Eliassen model is used to analyze the disparity between azimuthal velocity tendencies of selected pre–tropical storm vortices with low and high degrees of misalignment. Although no single factor completely explains the difference of intensification rates, greater misalignment is linked to weaker positive azimuthal velocity forcing near υm by the component of the mean secondary circulation attributed to heating by microphysical cloud processes. Of note regarding the dynamics, enhanced tilt only modestly affects the growth rate of kinetic energy outside the core of themore »
A cloud-resolving model is used to examine the intensification of tilted tropical cyclones from depression to hurricane strength over relatively cool and warm oceans under idealized conditions where environmental vertical wind shear has become minimal. Variation of the SST does not substantially change the time-averaged relationship between tilt and the radial length scale of the inner core, or between tilt and the azimuthal distribution of precipitation during the hurricane formation period (HFP). By contrast, for systems having similar structural parameters, the HFP lengthens superlinearly in association with a decline of the precipitation rate as the SST decreases from 30° to 26
- Award ID(s):
- 1743854
- Publication Date:
- NSF-PAR ID:
- 10363100
- Journal Name:
- Journal of the Atmospheric Sciences
- Volume:
- 79
- Issue:
- 2
- Page Range or eLocation-ID:
- p. 485-512
- ISSN:
- 0022-4928
- Publisher:
- American Meteorological Society
- Sponsoring Org:
- National Science Foundation
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