Abstract:Using Doppler weather radar data, retrieved wind field by single radar, and routine sounding and surface observations, the mesoscale characteristics of the occurrence and evolution of a waterspout storm over the northern Yellow Sea (off the coast of northern Shandong Peninsula) on 2 November 2014 are analyzed. Results show the incoming cold air, thermal boundary of the warm and moist air from the Yellow Sea, and convergence line between northwesterly and westerly winds on the coast of northern Shandong Peninsula are conducive to the occurrence of the waterspout storm. When the waterspout storms occurs, the maximum decibel reflectivity factor of radar PPI is 60 dBZ, the height of the maximum reflectivity is 2.0 km, the highest top of the storm is 4.5 km, and the maximum vertically integrated liquid (VIL) is 21 kg·m-2. The mesoscale characteristics of the wind field retrieved by single radar show there is wind convergence in the lower layer corresponding to wind divergence at 4.0 km and stronger southerly warm and moist air is conveyed from sea areas to the thunderstorm area during the occurrence and development of the waterspout storm. Mesoscale dynamic characteristics are that the maximum positive vorticity and convergence are below 1.0 km, and the dynamic characteristics at the initial stage of thunderstorm are positive vorticity and convergence in the lower layer and divergence field in the upper layer; the dynamic characteristics of developing thunderstorm are positive vorticity and convergence in the upper layer while there are no positive vorticity and convergence in the lower layer; the dynamic characteristics of mature thunderstorm are positive vorticity and convergence in the lower and upper layer. The cold air in the upper layer and the strong southerly air flow in the lower layer result in higher local vorticity and stronger convergence in the lower layer, which makes the warm and moist air in the lower layer ascend slantwise. The waterspout relates to the cold air and warm and moist air flow in the convergence area.