One of the components of the supercell definition includes persistence, namely, that the storm's circulation persists for at least 30-45 minutes. In some cases, a supercell may persist in a quasi-steady manner for several hours, and in extreme cases, the lifetime of a supercell may extend well beyond 4-5 hours. These long-lived supercells can produce significant severe weather along the majority of their paths, and on occasion, they generate a devastating combination of large hail and damaging winds.

Since these long-lived supercells are rare, they present a forecasting challenge. However, a few studies have addressed forecast issues related to supercell longevity. Some of the environmental parameters used to investigate supercell longevity have included storm-relative helicity (SRH), lifted condensation level (LCL) height, midtropospheric dryness, and the synoptic weather regime. No solid relationships have emerged from these studies, which leaves unsolved the problem of why a few supercells persist for many hours.

In the current study, we present findings from a preliminary investigation of supercells that persisted in a quasi-steady manner for greater than four hours. Specific attention is paid to local sounding parameters and the large-scale environment. For comparison purposes, we also examine shorter-lived supercells to determine if the environmental signals are the same or different from their longer-lived counterparts. The main finding of this preliminary work is that the large-scale environment plays a more significant role in determining supercell longevity than what can be inferred from individual soundings.