Characteristics and Structure of the Cumulonimbus Cloud with Waterspout over the Gulf of Finland

V. B. Popov, A. A. Sin’kevich, J. Yang, Yu. P. Mikhailovskii,
M. L. Toropova, Yu. A. Dovgalyuk, N. E. Veremei, and D. S. Starykh

The characteristics of the numulonimbus cloud with waterspout that has passed over the Gulf of Finland are analyzed. The characteristics were obtained from polarimetric Doppler weather radar, radiometer, and lightning detector data. The waterspout was formed close to the cyclone center. The analysis of instability indices revealed high atmospheric instability. The sinking of the rotational motion in the cloud before the waterspout generation is shown. The radar characteristics of the cloud at the moment of waterspout observation are considered in detail. It is concluded that good identifiers for the waterspout detection are the “Zdr column” and the zone in the lower part of the cloud with differently directed values of Doppler velocity and with the high values of velocity spectrum width.