Five mesosystems, occurring on 4 to 5 June 1953 in an area 500 by 600 mi near Chicago, were analysed with the use of data from regular synoptic stations. Four of the systems were of the well known type having a pressure-surge line, a thunderstorm high, and a wake depression. The fifth system, a trough 500 mi in length, traveled at the rate of 60 kn.
By using radar pictures taken every minute, the movement of echoes was also studied. The echo velocities, which were approximately 20 kn while a pressure-surge line was 100 mi distant, increased up to 40 kn with the approach of the line. The individual echoes in the line moved in an east-northeast direction while the pressure-surge line, oriented southwest to northeast, proceeded towards the south-southeast. The centers of the mesosystems moved in the same direction as the individual echoes in the squall line.
Hourly precipitation amounts accompanying each system were integrated with respect to time and “time integrated” precipitation charts were then constructed.
1 The research reported here was supported by the U. S. Weather Bureau under Contract No. Cwb 8950.
