ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 45 Issue 8 > 2019,45(8):1135-1148. DOI:10.7519/j.issn.1000-0526.2019.08.010 Prev Next
Investigation and Warning Practicability Analysis of the 6 July 2017 Tornado in Zhoukou City
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Abstract:
The severe convective weather in Zhoukou City on 6 July 2017 caused by a tornado was investigated and a general analysis of the circumstance and early warning practicability of tornado was made by using the high-level, surface and AWS data as well as the Doppler weather radar and FY-2G satellite data. The results show that the tornado disaster mainly affected the area with length of 4.5-5 km and width of 100-150 m between Xihua County and Huaiyang County of Henan Province, having considerable meso-γ scale vortex characteristics of the tornado with strength to Grade EF1 and Grade EF2 when strongest. (2) The tornado process was jointly influenced by the mid-latitude trough moving eastward and the warm-moist southwest airflow in the edge of subtropical high. The configuration of upper-level stream divergence and low-level jet offered heavy rain and tornado a favorable synoptically dynamic condition. The tornado was induced by the cyclonic convergent airflows on the convergence line which was between the severe rain cold outflow and the warm-moist airflow in the eastern part. Near the positive vortex center on the big va-lue of surface temperature, dew-point temperature and energy gradient may be where tornado could occur. (3) The Fuyang sounding data at 08:00 BT showed a strong conditional instable air where CAPE was 1712 J·kg-1 (3182 J·kg-1 corrected with surface temperature and dew point temperature at 14:00 BT), K index was 42℃, SWEAT index was 312, SI index was -4.5℃ and the PW was around 65 mm. The LCL was at a very low height of 959.2 hPa, wind vector difference of low-level vertical wind shear at 0-1 km was 10 m·s-1 or above, which offers a profitable circumstance conditions for the tornado. (4) On satellite images, the tornado occurred in the front of warm cloud bands whose TBB was under -72℃ where convective clouds developed vigorously. Lightning monitoring result showed the tornado was on the east side of the dense lightning flashes area. (5) On radar echo maps, the tornado occurred at the massive echo area on the front of northeast-southwest heavy rain echo banks. The occurrence of mesocyclone and its tornado features could give a reliable clue to the warning of tornado in the real-time operation. The enhancing of rotating speed and falling down of the height indicate the tornado would come to the ground surface. In a word, the results above could act as references for tornado monitoring and warning over the Huanghuai Plain.
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