Characteristics of the Meso-scale Environments of Storms Associated with Typhoon-spawned Tornadoes in Miyazaki, Japan

Abstract

In order to elucidate meso-scale environmental characteristics contributing the generation of a typhoonspawned significant tornado (F2) occurred in Nobeoka of Miyazaki prefecture, Japan in 2006, environmental and composite parameters in Miyazaki are examined in comparison with typhoon-spawned 3 tornadic events in Miyazaki and 16 nontornadic events using the forecast dataset of the operational nonhydrostatic mesoscale model of the Japan Meteorological Agency (JMA).It is found that the significant tornado in Nobeoka is accompanied by enhanced convectively unstable environment with large vertical wind shear, which is represented by a relatively large convective available potential energy based on mean parcel in the lowest 500 m layer above ground level (AGL) (mlCAPE) and significantly large shear parameters (e.g., storm relative helicity; SRH) compared with other tornadic and nontornadic events. We also discuss synoptic condition producing these characteristic environments along with the comparison of the environment for the tornadic supercells and hurricane-spawned tornadoes in the U.S. IntroductionFor the mitigate of disastrous damages due to tornadoes, it is important to improve the potential predictability for the outbreak of tornadoes. Although there are several statistical studies to characterize environmental parameters for the occurrence of tornadoes in the U.S. (Rasmussen 2003;Thompson et al. 2003), only few studies have been conducted in the similar approach for the outbreaks of tornadoes in Japan (e.g., Sakurai and Kawamura 2008). In particular, the distinct characteristics of environments associated with tornadic storms in Japan have not been elucidated in comparison with those of nontornadic events.On the other hand, Niino et al. (1997) indicated that tornadoes in Japan took place in various synoptic conditions such as extratropical cyclone, typhoon (or tropical cyclone), cold front, winter monsoon and stationary front, and also in various geographical locations. It is also well known that the environmental parameters such as CAPE in Japan critically depend on the locations and seasons as well as synoptic conditions (Chuda and Niino 2005). Thus, it is very hard to extract common characteristics of environmental parameters for the genesis of tornadoes using all tornadic events in Japan. Here, we focus instead on tornadoes in a specific location and synoptic condition in Japan, and try to reveal their environmental characteristics.On 17 Sep. 2006, a significant tornado associated with typhoon T0613 took place in Nobeoka of Miyazaki prefecture in Japan (hereafter, Nobeoka-Tor event, Fig. 1) and caused serious damages (F2 scale) (Miyazaki District Meteorological Observatory 2006). This typhoon caused also two other F1-scale tornadoes in Hyuga and Nichinan of Miyazaki on the same day. Mashiko (2007) shows horizontal distribution of environmental parameters associated with the Nobeoka-Tor by a simulation with a high-resolution nonhydrostatic model of the JMA. Hence, by focusing on typhoonspawned tor...

Analysis of the Three-Dimensional Structure of the Misocyclones Generating Waterspouts Observed by Phased Array Weather Radar: Case Study on 15 May 2017 in Okinawa Prefecture, Japan

“…In particular, a large SRH 1km (SRH between the ground and 1 km in height) is an indicator of a mesocyclone relatively close to the surface, which is an indicator of a tornado in a supercell [24,25]. The environment for tornado occurrence in Japan differs from that in North America in that the middle troposphere is often warm and humid and relatively small CAPE = 1185 J kg −1 has been reported as the atmospheric environmental condition during tornado occurrence [26].…”