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Abstract
This paper discusses the meteorological conditions associated with tropical cyclone formation in the north Indian Ocean during the 1979 FGGE year. Seven developing systems are composited together using FUGE Ill-b analyses to show the common circulation features surrounding developing cloud clusters. Three systems are further discussed to show different environmental influences on the low-level buildup of circulation during formation. The characteristics of these three disturbances’ 200 mb outflow patterns and a general discussion of north Indian Ocean tropical cyclone activity are also given.
Results show that tropical cyclone formation generally follows the initial increase of strong low-level winds on one side (either equatorial or polar) of a precyclone disturbance. This early buildup of wind appears to result from environmentally forced asymmetric wind surge action. Some of this increase appears to result from inward advection of velocity, but part of the increase seems to occur in situ. These initial strong azimuthal wind asymmetries are gradually reduced as the winds spread more evenly around the disturbance. A basic cyclone development process is the evolution of the low tropospheric flow from initial asymmetrical now (shear vorticity) to a more symmetrical circulation (curvature vorticity).
Abstract
This paper discusses the meteorological conditions associated with tropical cyclone formation in the north Indian Ocean during the 1979 FGGE year. Seven developing systems are composited together using FUGE Ill-b analyses to show the common circulation features surrounding developing cloud clusters. Three systems are further discussed to show different environmental influences on the low-level buildup of circulation during formation. The characteristics of these three disturbances’ 200 mb outflow patterns and a general discussion of north Indian Ocean tropical cyclone activity are also given.
Results show that tropical cyclone formation generally follows the initial increase of strong low-level winds on one side (either equatorial or polar) of a precyclone disturbance. This early buildup of wind appears to result from environmentally forced asymmetric wind surge action. Some of this increase appears to result from inward advection of velocity, but part of the increase seems to occur in situ. These initial strong azimuthal wind asymmetries are gradually reduced as the winds spread more evenly around the disturbance. A basic cyclone development process is the evolution of the low tropospheric flow from initial asymmetrical now (shear vorticity) to a more symmetrical circulation (curvature vorticity).
The history of meteorology has taught us that weather analysis and prediction usually advances by a series of small, progressive studies. Occasionally, however, a special body of work can accelerate this process. When that work pertains to high-impact weather events that can affect large populations, it is especially notable. In this paper we review the contributions by Vernon F. Dvorak, whose innovations using satellite observations of cloud patterns fundamentally enhanced the ability to monitor tropical cyclones on a global scale. We discuss how his original technique has progressed, and the ways in which new spaceborne instruments are being employed to complement Dvorak's original visions.
The history of meteorology has taught us that weather analysis and prediction usually advances by a series of small, progressive studies. Occasionally, however, a special body of work can accelerate this process. When that work pertains to high-impact weather events that can affect large populations, it is especially notable. In this paper we review the contributions by Vernon F. Dvorak, whose innovations using satellite observations of cloud patterns fundamentally enhanced the ability to monitor tropical cyclones on a global scale. We discuss how his original technique has progressed, and the ways in which new spaceborne instruments are being employed to complement Dvorak's original visions.
