Abstract:

To gain an in-depth understanding of the formation mechanisms of tornadoes in Henan and enhance the accuracy of tornado monitoring and early warning operations, this study comparatively analyzes the synoptic background, environmental conditions, and radar characteristics of three tornado events in northeastern Henan Province using conventional meteorological observations, ERA5 reanalysis data, and Doppler radar data, and summarizes local tornado forecasting and warning indicators. The results show that: (1) All three tornadoes occurred over the plain areas of Puyang City in northeastern Henan during the period from June to July. The “22·6” and “23·7” tornadoes occurred around midday, whereas the “09·7” tornado occurred in the evening. The “09·7” and “23·7” events were accompanied by regional short-duration heavy rainfall, whereas the “22·6” tornado featured localized short-duration heavy rainfall and minor hail.(2) Although all three events developed under the influence of the Northeast China Cold Vortex, unlike the upper-level cold advection-forced “22·6” tornado, the “09·7” and “23·7” tornadoes were warm advection-forced. Surface convergence lines or mesoscale cyclones provided dynamic forcing for all events. (3) All three events exhibited low lifting condensation levels and strong low-level vertical wind shear. The “09·7” and “23·7” tornadoes featured thicker near-surface moisture layers and stronger low-level wind shear, whereas the “22·6” event showed a pronounced dry layer, a lower wet-bulb zero level, and the greatest temperature difference between 850 and 500 hPa. (4) Prior to tornadogenesis, the parent convective systems of all three events showed enhanced echo centers and evolved into bow-shaped, hook-shaped, or vortex-like structures. Velocity fields exhibited the coexistence of low-level cyclonic convergence and mid-level rotational ascent. The “22·6” event had the strongest echo intensity but weak vortex signatures and a shallow structure; the “09·7” tornado had the strongest vortex intensity and deepest rotational thickness; the “23·7” event had the weakest echo intensity and lowest tornado vortex signature value (potentially radar-limited), but a greater vertical depth. This study provides a reference for forecasting and warning services for tornadic severe weather.

Key words: tornado, Northeast Henan, synoptic background, environmental conditions, radar characteristics