Investigating the Relationship of Jet Streams with the Intensity and Track of North American Lee Cyclones

Past research associates the enhancement of surface cyclones with rising motions below the right-entrance and left-exit quadrants of an upper-level jet streak. The position of cyclones greater than or equal to two days in duration, counted from the first occurrence that the cyclone was located between 30-60°N and 90-120°W, were examined in relation to jet quadrants for January, March and October of 1948-2002. To evaluate the synoptic influences of jet streaks, several groups of similar geographical cyclone tracks, within the 95th percentile of longevity, were created. A total 58 cyclones were included in these groups: each group contained a minimum of three individual cyclones while five cyclones were not categorized into any group as a result of their dissimilar geographical tracks. The “Cleveland Superbomb” of January 1978 was categorized into one of the groupings and was used as a case study. Mean sea level pressure (MSLP) and 300 hPa vector wind (Jet Wind) composite maps were constructed for both, the groups and the case study. Using these maps, the mean track and intensity of the cyclones were compared to close proximity jet streaks and streams. The results indicated that the position of a surface cyclone relative to a particular jet quadrant is one of several factors that influence the intensification of a surface cyclone. However, the consistency of surface cyclones located in the left exit quadrant of a jet streak suggests that this is a viable indicator of surface cyclone intensification.