Cloud-top characteristics documentation: Test of an automated method

Measurements of cloud-top area, eccentricity and mean geographic location for mesoscale convective systems (MCSs), have been calculated by an automated method over their life cycle. The algorithm utilizes digital infrared imagery from GOES-8, received through Internet. The MCSs are isolated at a threshold of -32°C, if the area at this threshold exceeds 32000 km2, then the mesoscale system is documented. Embedded cloud clusters (CC) with a threshold of -52°C are also identified if the area of these clusters is at least 64 km2. Documentation includes the number of cloud clusters embedded, the minimum infrared temperature (Tir) for each cluster, the average Tir for the whole system and their position. The algorithm also includes an analysis in the subsequent image (time of separation is variable) to locate possible candidates representing the same MCS at the subsequent image, and calculates the velocity of propagation of the whole system and of the largest cloud cluster. All operations are performed within the bounds of a defined image subsector, within SA mid-latitudes. The method provides acceptable results as long as storm cloud tops are isolated from one another.