Lake-Effect Cloud Bands as Seen From Weather Satellites

Satellite photographs of the TIROS and ESSA series were examined for the presence and dimensions of lake-effect clouds over the Great Lakes and Gulf of St. Lawrence. It was found that nearly all lake-effect clouds occurred when the 850-mb temperature was more than 13 C colder than the lake surface temperature. The clouds were organized into parallel bands resembling but having larger dimensions than cloud streets. Enlarged cloud bands were found which were 2.5 times larger than normal lake-effect bands. These enlarged lake storms had preferred origins and appear to be generated by frictional differences between land and water, by the geometry of the body of warm water with respect to the prevailing wind, and by certain urban influences.