Trochoidal Motion of the Eye of Typhoon 8019

Abstract

A marked periodic oscillation of trochoidal motion was found in the track of the eye fixed by radar and satellite for the typhoon 8019 (WYNNE). Five remarkable oscillations with the period of 5hr-8 hr and the maximum amplitude of 23km were observed for 36 hrs by land-based Miyakojima radar. The amplitude decreased with decreasing period. The analysis of PPI echo image shows that the center of typhoon eye did not agree with the system center of the whole typhoon circulation; and the eye shifted and rotated counterclockwise around the system center. In the occurrence of the phenomenon, the "double eye" structure of the echo and the double wind maxima were observed in the typhoon; the outer and inner eyewalls have diameters of about 260km and 30km, respectively. In particular, elliptical circulation of the pressure and wind fields and resulting the rectangular-shaped echo configuration were found an area inside the radius of the outer eyewall. The rectangle and elliptical circulation rotated counterclockwise around the system center with the same period of that of trochoidal motion. Both features were inscribed in the outer eyewall ring with radius of approximately 130km. The eye traced the subpoint corresponding to one of the focus of the ellipse on the major axis; consequently, the trochoidal motion took places in the typhoon circulation. However, it was not clear why the eye was shifted.

Revisiting the steering principal of tropical cyclone motion in a numerical experiment

“…The tropical cyclone center rotates cyclonically around the mean track, in agreement with previous observational and numerical studies (Lawrenece and Mayfield, 1977;Muramatsu, 1986;Itano et al, 2002;Willoughby, 1988;Nolan et al, 2001). It is found that the small-amplitude trochoidal motion cannot be accounted for by the effect of the conventional steering, although the contribution of the HA term plays an important role in the fluctuations.…”

“…This displacement is less than the size of the tropical cyclone eye. In general, the tropical cyclone center rotates cyclonically relative to the mean track position, in agreement with previous observational and numerical studies (Lawrenece and Mayfield, 1977;Muramatsu, 1986;Itano et al, 2002;Willoughby, 1988;Nolan et al, 2001). In association with the trochoidal motion of the tropical cyclone center, as suggested by Nolan et al (2001), substantial potential vorticity redistribution and mixing can be observed in the inner-core region (Fig.…”

“…Based on radar data and satellite images, many studies have documented the oscillation of a tropical cyclone track with respect to its mean motion vector (e.g., Jordan and Stowell, 1955;Lawrence and Mayfield, 1977;Muramatsu, 1986;Itano et al, 2002;Hong and Chang, 2005). The periods of track oscillations range from less than an hour to a few days (Holland and Lander, 1993).…”

Hurricane Eyewall Replacement Cycle Thermodynamics and the Relict Inner Eyewall Circulation

“…Visible satellite imagery (not shown) reveals that the relict inner eyewall circulation had orbited around the larger, developing eye and produced trochoidal motions of the storm center. Trochoidal motions often accompany concentric eyewall structures (Jordan 1966;Oda et al 2006;Muramatsu 1986), as well as when only a single eyewall is present (Liu et al 1999;Nolan et al 2001;Marks et al 2008;Hendricks et al 2009). The air mass within the relict inner eyewall circulation maintained its identity and characteristics as it orbited through the much drier environment of the developing eye.…”

The Hurricane Rainband and Intensity Change Experiment: Observations and Modeling of Hurricanes Katrina, Ophelia, and Rita

“…As storms intensify, asymmetries in the form of vortex Rossby waves can lead to polygonal eyewalls (Muramatsu 1986), mesovortices (Marks and Houze 1984;Black and Marks 1991), and even a complete breakdown and rearrangement of the inner-core structure (Schubert et al 1999;Nolan and Montgomery 2002). Such an evolution has been observed directly (Kossin and Eastin 2001).…”