Radar Precipitation Echo and Satellite Cloud Observations of a Maritime Cyclone1

Abstract

Satellite-observed cloud patterns for five days during the evolution of a major, extratropical maritime cyclone associated with a strong Ω-shaped blocking pattern were studied for the period when the storm existed over a radarscope data collection network. Cloud distributions at 24-hr intervals were compared with the surface and upper-level synoptic conditions to ascertain cloud-synoptic pattern precipitation pattern relationships. Precipitation distributions are shown in relationship to the cloud features which appear to be characteristic of extratropical maritime cyclones. In general, the very low percentage of clouds that precipitate at any given time is strongly re-emphasized, as well as the limited area within a storm in which precipitating clouds are found. Shower patterns within cellular type convective clouds are shown to develop in the same configuration as the clouds and to be subject to diurnal effects. These showers were found to have lasted at least two hours, a considerably longer period than comparable continental air-mass showers. Minor cloud vortices were found which persisted along regions of confluence of contrasting air masses around the periphery of the major spiral cloud pattern associated with the storm; these minor vortices appeared to rotate with the gross cloud pattern and were loci of heavy precipitation activity.