Abstract
An elevated supercell from the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) on 6 May 2010 is investigated. Observations show that the supercell formed over a stable inversion and was likely decoupled from the surface. Quintessential features of a supercell were present, including a hook echo (albeit bent anticyclonically) and midlevel mesocyclone, and the storm was quasi steady during the observing period. A weak surface cold pool formed, but it was apparently devoid of air originating from midlevels. Idealized modeling using near-storm soundings is employed to clarify the structure and maintenance of this supercell. The simulated storm is decoupled from the surface by the stable layer. Additionally, the reflectivity structure of the simulated supercell is strikingly similar to the observed storm, including its peculiar anticyclonic-curving hook echo. Air parcels above 1 km reached their LFCs as a result of the simulated supercell’s own dynamic lifting, which likely maintained the main updraft throughout its life. In contrast, low-level air in the simulation followed an “up–down” trajectory, being lifted dynamically within the stable layer before becoming strongly negatively buoyant and descending back to the surface. Up–down parcels originating in the lowest 100 m are shown to be a potential driver of severe surface winds. The complementary observations and simulations highlight a range of processes that may act in concert to maintain supercells in environments lacking surface-based CAPE.
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