ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 40 Issue 6 > 2014,40(6):668-677. DOI:10.7519/j.issn.1000-0526.2014.06.003 Prev Next
Doppler Radar Product Features and Warning of Non Supercell Tornadic Storms
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Abstract:
Six non supercell tornadic storms in Shandong Province were analyzed based on Doppler radar data from Jinan and Yantai in combination with environmental parameters and weather events, of which 4 tornado processes were produced in the condition of backward tilting trough and one tornado process was produced in the condition of northwest flow, and moreover 2 tornadoes were in EF0 scale, 3 in EF1 scale, and one in EF2 scale. The results showed that the environment situations are conducive for thunderstorms on 31 July 2006, 18 July 2007 and 3 August 2009. High humidity in the lower level and the 0-1 km vertical wind shear ≥7 m·s-1 play an important role in the occurrence of non supercell tornadoes. The gate to gate azimuthal shear (i.e., the gate to gate velocity difference) ≥20 m·s-1 in the 0.5° elevation angle mean radial velocity product, or the gate to gate azimuthal shear ≥15 m·s-1 in the 0.5° elevation angle storm relative mean radial velocity product can be used as a warning criteria for non supercell tornadoes. Four tornadoes form during the rapidly developing stages of thunderstorms, especially the cell tops markedly increase within 6 min. The strong updrafts that quickly build up within storms are the main incentives for the occurring of tornadoes. The rapid developing of storm needs strong updraft. The strong updrafts stretch the small vortex existing in the low level convergence line quickly, thus, the small vortex movement gets further developed, inducing small scale intense shear, and causing tornadoes to occur.
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