Weather Classification and Forecast Focuses of Extreme Thunderstorms and Gales on Background of Cold Votex in Shandong
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Abstract:
In order to gain a deeper understanding of the statistical characteristics and forecasting focuses of extreme thunderstorm gusts with a magnitude of 11 or above that occur in Shandong under the background of cold vortices and cause disasters, the paper analyses the large-scale circulation background, radar characteristics, vertical wind shear, and parameter features related to the intensity potential and momentum downward transmission of extreme thunderstorm winds. This is done by analysing the maximum hourly wind speed of automatic precipitation data, MICAPS data, radar wind profile, North China radar, lightning positioning data and NCEP reanalysis data during 2013-2021, through statistical methods, weather diagnosis, and synthetic analysis, etc. The main conclusions are as follows: (1) The extreme thunderstorm gale events above grade 11 are divided into 6 categories: low trough type, northwest airflow type, transverse trough type, upper cold vortex type, subtropical high marginal type and warm shear type. (2) There are five types of thunderstorms that produce extreme thunderstorm wind: bow echo, multi-cell storm, squall line, supercell and ordinary thunderstorm, among which bow echo and multi-cell storm are the main forms, accounting for 63% of the total number of occurrences. Squall lines and supercells are also forms of extreme thunderstorm winds, accounting for 17% and 13% respectively. (3) The middle front of the bow echo is the region with a high probability of extreme thunderstorm and gale. The right front of the moving direction of the multi-cell storm, the front of the squall line and the right front of the moving direction of the supercell are also the key areas of the extreme thunderstorm and gale. (4) When the extreme thunderstorm and gale occur, the top height of the echo is usually above 15 km. The extreme thunderstorm gale appears in the front or right front of the moving direction of the high centre of the Echo Top. (5) When the strong hourly pressure change over 2.5 hPa appears on the ground, the cold pool centre is lower than the surrounding atmosphere, and the environmental wind field in the middle and lower troposphere is obviously strengthened, the moving direction of the storm should be combined, to determine in advance the direction of the storm ahead, especially the right front, whether there is the possibility of extreme thunderstorm gale.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.