STUDY OF AN UNEXPECTED CONVECTIVE STORM

The occurrence of a severe storm in the Argentine littoral has been an alyzed. Although general atmospheric conditions were not favorable to the development of deep convection, this storm produced strong winds a nd hail of considerable intensity. Its occurrence was associated with the entrance of a pulse of humid air at low levels and could be relate d to the development of two vorticity centers in the region. Atmospher ic conditions existing above a low-level inversion are used to simulat e two possible clouds, with base altitudes at 2200 and 3000 m and updr aft speeds reaching maximum values of 27 and 29 m s(-1), respectively. It is noted that the base temperature of about 13 degrees C, found fo r the first cloud, can be correlated with the prevalence of frozen dro p embryos, observed in an analyzed hailstone sample. Hailstone vertica l trajectories are simulated in both modeled clouds, assuming spheroid al and spherical particles and assigning different values to the drag coefficient C-d. (C) 1997 Elsevier Science B.V.