The Role of Vertical and Horizontal Wind Shear in the Development of Quasi-tropical Cyclones

Cloud-resolving modeling has been implemented to investigate a lifecycle of two quasi-tropical cyclones (QTCs) over the Black and Mediterranean seas in September 2005 and 2018. The formation of the Mediterranean QTC under the influence of the PV streamer and the problems of predicting this phenomenon are considered. The influence of the mesocyclone wind system on cumulus convection is studied, while mesocyclone winds are assumed to be axisymmetric for simplicity. It has been found for the largest and most intense QTCs that vertical wind shear may lead to the formation of supercellular storms, but to a rather limited extent and as a result of deviations of mesocyclone currents from the axial symmetry. In small intense QTCs, horizontal wind shear can suppress convection over a certain range of distances from the center of a cyclone, leading to a release of latent heat closer to it.