Time of initial circulation detection is also depicted in UTC, and denoted by a marker specific to each circulation track every five minutes thereafter. The synoptic and mesoscale environment of early 14 June 1998 was characterized by strong southwesterly low-mid level winds ahead of a trough in the Plains. Convection developed well north of a warm frontal boundary which extended from an area of low pressure over eastern Kansas southeast through northeastern Arkansas. A steep lapse rate of 8 C km-1 was present in the elevated mixed layer between 800 and 550 mb. This increase in the SR helicity was due to the strengthening of the wind below 3 km and backing of the wind below 1 km from 0930 to 1111 UTC, leading to a clockwise turning hodograph in the lowest 3 km as depicted in Figure 3.
Black dot represents storm motion vector.
The second MCS developed between 0900 and 1000 UTC, as two parallel lines of convection, oriented northeast-southwest, rapidly formed 90 to 120 km northwest of St. Louis. The second line gradually merged with the leading line after 1030 UTC, resulting in the intensification of the leading convective line. The first circulation formed at 1050 UTC in the intensifying storm's inflow notch. Shortly after the development and rapid intensification of Circ. Much of the wind damage occurred just south of the path of Circ.