Finescale Doppler Radar Observation of a Tornado and Low-Level Misocyclones within a Winter Storm in the Japan Sea Coastal Region

Abstract

Life histories of low-level misocyclones, one of which corresponded to a tornado vortex within a winter storm in the Japan Sea coastal region on 1 December 2007, were observed from close range by X-band Doppler radar of the East Japan Railway Company. Continuous plan position indicator (PPI) observations at 30-s intervals at the low-elevation angle revealed at least four cyclonic misocyclones within the head of the comma-shaped echo of the vortical disturbance under winter monsoon conditions. The meso-b-scale vortical disturbance developed within the weak frontal zone at the leading edge of cold-air outbreaks.High-resolution observation of misocyclones revealed the detailed structures of these misocyclones and their temporal evolution. As the parent storm evolved, a low-level convergence line was observed at the edge of the easternmost misocyclone. This convergence line was considered to be important for the initiation and development of the misocyclones and the tornado through vortex stretching. The strongest misocyclone gradually intensified as its diameter contracted until landfall, and then began to dissipate soon after landfall. The temporal evolution of the misocyclones through landfall is discussed.Surface wind and pressure variations suggested a cyclonic vortex passage, which was consistent with the passage of the radar-derived misocyclone. The observed pressure drop was also consistent with that computed from the cyclostrophic equation for the modified Rankine vortex. The observed behavior of two adjacent misocyclones was primarily consistent with the rotational flow associated with the other misocyclone. The generation and development processes of the tornado and misocyclones are discussed.

Rapid Intensification of a Winter Misocyclone under an Isolated Convective Cloud after Landfall

“…The intensification of the misocyclone after landfall is apparently in contrast to previous reports of winter tornadic vortices and misocyclones developing over the Japan Sea and dissipating after landfall (Kobayashi et al 2007;Inoue et al 2011;Kato et al 2015). According to the present results, the evolution of the misocyclone is probably related to the parent cloud's development.…”

“…Many winter misoscale vortices including winter tornadoes (hereafter called winter misocyclones) are generated and developed over the Sea, and travel with the monsoon to the coast. Such winter misocyclones have been found in various mesoscale cloud systems including a convective cloud developed in part of a cloud band (Kobayashi et al 2007), a band-shaped cloud at the leading edge of a frontal zone (Inoue et al 2011), and a locally developed snow cloud band (Kato et al 2015). These previous studies reported changes in the structure of those vortices after landfall such as the dissipation of the vortices on land possibly caused by the effect of ground surface friction on the angular momentum of the vortices.…”

History and Applications of Dust Devil Studies

“…Inoue et al (2011) successfully detected vortices such as tornados and mesocyclones, although not dust devils, during a winter storm event with the use of a low-level scanning X-band Doppler radar. Fujiwara et al (2011Fujiwara et al ( , 2012) used a three-dimensional scanning Doppler lidar to detect dust-devil-like vortices that develop in the daytime under fair-weather convective conditions over an urban area.…”

Structure of Two Adjacent Shear Lines Accompanied by Wind Gusts in the Japan Sea Coastal Region during a Cold-Air Outbreak on 12 December 2010

“…Representative disturbances accompanied by a wind shear and a tornado are a synoptic-scale cold front (e.g., Okazaki 2009) and the Japan-Sea Polar-Airmass Convergence Zone (JPCZ) (e.g., Kobayashi 2002) that extends from the base of the Korean Peninsula to the Hokuriku district. Mesoscale shear lines in snowbands also occasionally cause meso-γ-scale vortices (Kawashima and Fujiyoshi 2005) and micro-scale vortices including a tornado (Mashiko et al 2009;Inoue et al 2011). In recent decades, many studies have been conducted to reveal the detailed structure and growth mechanisms of micro-to meso-β-scale vortices from Doppler radar data and through numerical simulation (e.g., Kawashima and Fujiyoshi 2005;Kobayashi et al 2007;Mashiko et al 2009;Inoue et al 2011).…”

“…Mesoscale shear lines in snowbands also occasionally cause meso-γ-scale vortices (Kawashima and Fujiyoshi 2005) and micro-scale vortices including a tornado (Mashiko et al 2009;Inoue et al 2011). In recent decades, many studies have been conducted to reveal the detailed structure and growth mechanisms of micro-to meso-β-scale vortices from Doppler radar data and through numerical simulation (e.g., Kawashima and Fujiyoshi 2005;Kobayashi et al 2007;Mashiko et al 2009;Inoue et al 2011). However, the structure of the shear lines, which cause such vortical disturbances and/or wind gusts, are still poorly understood except for the JPCZ (e.g., Nagata et al 1986;Nagata 1991).…”