Definition of the mean environmental steering flow for TCM-90 tropical cyclones
Loading...
Authors
Bohner, Richard H., Jr.
Subjects
Limited region/global analysis
Mean environmental flow
TCM-90
Tropical cyclone motion
wavenumber bandpass filtering
Mean environmental flow
TCM-90
Tropical cyclone motion
wavenumber bandpass filtering
Advisors
Elsberry, Russell L.
Date of Issue
1992-09
Date
September 1992
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
A definition for the environmental steering flow in the vicinity of the TCM-90 tropical cyclones is sought by low-pass filtering the Naval Operational Global Atmospheric Prediction System deep-layer mean u- and v- velocity and geopotential height fields. One-dimensional and two-dimensional Fourier decompositions in a limited region (120(o) long) and in a global region are compared with six wavenumber low-pass filters (1-6, 1-9,...,1-21). The measure of goodness of the environmental steering flow interpolated to the storm position was to determine the minimum standard deviation of the propagation vector (defined as difference between storm motion and the steering estimate) for all six storms and the ensemble. The best results were found for either the limited and global region one-dimensional Fourier analyses of the u and v wind fields with a low-pass filter that included only wavenumbers 1 -15. The sic TCM-90 tropical cyclones were subsequently analyzed using this definition of the steering flow to estimate the propagation vectors and to examine the linear shear and relative vorticity gradients of the environmental flow. Except for early stages of storms in low latitude, the low-pass filtered analyses provided steering vectors consistent with the changing translation directions. However, the translation speeds tended to exceed the storm motion and lead to more westward propagation vectors than expected. These propagation vectors tended to be almost perpendicular to the absolute vorticity gradient vector.
Type
Thesis
Description
Series/Report No
Department
Meteorology
Organization
Naval Postgraduate School
Identifiers
NPS Report Number
Sponsors
Funder
Format
78 p.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
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.