The Role of Hurricane Ernesto (2006) in a Predecessor Rainfall Event

One of the greatest threats to life and property from landfalling tropical cyclones (TCs) is freshwater flooding. The development of downstream mesoscale convective systems ahead of TC landfall can further exacerbate flooding associated with the TC. However, is the development of these mesoscale convective systems, referred to as predecessor rainfall events (PREs), always dependent on the presence of an upstream TC? The purpose of this study is to elucidate the role of TC Ernesto (2006) in the development of a PRE over North Carolina and Virginia. Numerical modeling was performed to determine what changes occurred to the advection of moisture into the PRE region, upper level jet strength, and PRE location and intensity after removing the TC vortex for model experiments initialized prior to PRE development. Experimental runs found that the TC did not enhance moisture or precipitation within the PRE region in the case of TC Ernesto. The implications of these results show that TCs do not always enhance downstream mesoscale convective systems, and suggest that care must be taken in the attribution of PRE events to upstream TCs.