The Role of Midtropospheric Winds in the Evolution and Maintenance of Low-Level Mesocyclones

Abstract

Abstract Using a three-dimensional numerical model, supercell simulations initialized in environments characterized by hodographs with large curvature in the lowest 3 km and a range of linear midlevel shears are investigated. For low values of the midlevel shear (0.005 s−1), the storm develops a mesocyclone at the lowest model level within the first hour of the simulation. The gust front starts to move ahead of the main updraft and cuts off the inflow to the storm by approximately 2 h, resulting in decay of the initial storm and growth of a new rotating storm on the outflow. As the midlevel shear increases to approximately 0.010 s−1, the initial development of the low-level mesocyclone is delayed, but the mesocyclone that develops is more persistent, lasting for over 2 h. Further increases of the shear to 0.015 s−1 result in the suppression of any low-level mesocyclone, despite the presence of intense rotation at midlevels of the storm. We hypothesize that differences in the distribution of precipitation ...