A numerical study of the development of convection on 21 July 2001 over Cuba

Abstract

On 21 July 2001 several severe storms developed over the eastern region of Cuba in the afternoon hours and hail was observed. A numerical simulation was performed to study the structure and evolution of convection on that day with the aid of the 1800 UTC sounding. Furthermore, three more simulations were performed to study the effect of the vertical wind profile on the severity of the simulated storms. The Advanced Regional Prediction System model (ARPS) was used for this numerical study. An initial storm that later split into two new storms that moved to the right and to the left of the mean wind was simulated. The right-moving storm (RS) developed more than the left-moving one (LS). Hail was observed in most of the simulation time but the largest amount of hail reached the surface after the splitting in the RS. Two mechanisms were responsible for the inhibition of the LS. First, a vertical pressure gradient that acted against the main updraft development. Second, the entrainment of drier and colder air in the LS’s updraft at midlevels that came directly from the downdraft region. The wind shear above 10 km was favorable for a larger hail production, intensity and maximum values at the surface and a larger precipitation area. When the wind shear below 7 km was removed, the total volume of precipitation, the intensity of precipitation, maximum horizontal wind and maximum updraft were the largest compared to the other simulations. The LS was not inhibited in this case and both storms reached the same strength. The mechanisms that inhibited the development of the LS were not present in this simulation.