A Numerical Study of Intense Convection That Caused the Tornado in Blagoveshchensk on July 31, 2011
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merical Study of Intense Convection That Caused the Tornado in Blagoveshchensk on July 31, 2011 S. O. Romanskiia*, E. M. Verbitskayaa, and P. B. Sulyandzigab a
Far Eastern Regional Hydrometeorological Research Institute, ul. Fontannaya 24, Vladivostok, 690600 Russia b Computing Center, Far Eastern Branch, Russian Academy of Sciences, ul. Kim Yu Chena 65, Khabarovsk, 680000 Russia *e-mail: [email protected] Received January 10, 2019 Revised July 29, 2019 Accepted October 1, 2019
Abstract—The results of the numerical simulation of intense convection that caused the tornado in the city of Blagoveshchensk on July 31, 2011 are presented. The WRF-ARW nonhydrostatic mesoscale model on the nested grids with the spacing to 500 m is used for simulations. It is found that the tornado was initiated by the meso-g vortex associated with a quasilinear convective system at the height of 700–900 m. The mesovortex was generated when the wind shear in the lower 2-km layer was 21–27 m/s and convective available potential energy was to 1800 J/kg. The position and center of the mesovortex were specified by the values of vorticity and the Okubo–Weiss number. The simulated tornado was formed close to this mesovortex. The main contribution to the intensification of vertical velocity in the tornado was made by the perturbations of pressure and buoyancy and that to vorticity was made by the horizontal advection. The simulated time of occurrence, location, and duration of the event slightly differ from the real ones. DOI: 10.3103/S1068373920060035 Keywords: Tornado, mesovortex, severe weather events, quasilinear convective system, numerical simulation, the Far East
1. INTRODUCTION Tornados are certainly among the most severe weather events. The dense network of ground-based observation stations, modern Doppler weather radars, and satellite observations are needed to detect the signs of tornado formation. For example, the authors of [7] note that the number of tornados registered in Europe, especially in the northern and eastern parts, is underestimated, although the total number of the registered events has considerably increased since 1995. The similar results were also obtained for China [9]. In Russia, severe tornados are also observed, and successful attempts to simulate them based on the mesoscale numerical models have been recently made [1–3]. The observation network in the Russian Far East is sparse, modern weather radars are almost absent; therefore, the numerical modeling is the only tool for studying the processes leading to the tornado formation and for revealing their local parameters. This is especially important for developing and improving methods for the prediction of rare convective hazards and for warning the public about the impending danger. The present paper considers the results of modeling the intense convection that induced the severe tornado in Blagoveshchensk on July 31, 2011. In the afternoon on July 31, 2011, developed cumulonimbus clouds (Cb) with showers, thunderstorms, and tornado were formed in the areas of Ch
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