A Climatological Study of Jet Streak Acceleration Events and Downstream Impacts

Archambault et al. (2013), hereafter A2013, showed that high-impact weather events can occur downstream from recurving tropical cyclones (TC) that undergo extratropical transition and interact strongly with the midlatitude flow.  These events, which can occur half a hemisphere away from the TC, are the result of jet streak intensification and downstream wave amplification triggered by a prolonged period of strong negative PV advection by the divergent component of the wind in the TC outflow region. The present study extends and generalizes the work of A2013 by obtaining a global climatology of all strong episodes of negative PV advection by the divergent component of the wind (here called jet acceleration events or JAEs). Using global TC data from the IBTrACS database from 1979-2015, it is first demonstrated that JAEs can also occur with non-recurving TCs and that TC-related JAEs are confined to the western North Pacific basin. 

The hypothesis that JAE events can occur outside of the western North Pacific TC context with similar downstream impacts to those associated with TCs is tested next. The global climatology showed that JAEs were found throughout the year, particularly in fall and winter months, and in four preferred regions: near Japan, in the central North Pacific Ocean, over the Great Lakes region of North America and just east of Australia. Composite increases in downstream meridional index and 250-hPa wind speed were similar to those reported by A2013 for western North Pacific recurving TCs. This suggests that a prolonged period of strong negative PV advection by the divergent component of the wind at any time of year can engender high impact downstream weather. A few illustrative winter examples are shown.

Reference:

Heather M. Archambault, Lance F. Bosart, Daniel Keyser, and Jason M. Cordeira, 2013: A Climatological Analysis of the Extratropical Flow Response to Recurving Western North Pacific Tropical Cyclones. Mon. Wea. Rev., 141, 2325–2346.