Observations of storm scale boundary evolution within the 23 May 2007 Perryton, TX supercell

Baroclinity within the forward-flank downdraft has long been thought to play an important role in low-level mesocyclogenesis and tornadogenesis. However, direct observations from within the forward-flank have been difficult to obtain due to the hazardous environment for deployment.

On May 23rd, 2007, Project MOBILE (Multiple Observations of Boundaries in the Local-storm Environment) deployed twenty StickNet probes as well as a four probe mobile mesonet array within a high-precipitation tornadic supercell south of Perryton, TX. Data were collected within the precipitation core of the storm while a weak tornado was ongoing as well as within both the forward and rear-flank downdrafts as the mesocyclone passed through the instrument array.

The supercell exhibited very large maximum deficits of both virtual potential temperature and equivalent potential temperature within the forward-flank downdraft throughout the observation period, which has been shown to be more typical of nontornadic supercells. Despite these large deficits, a rapid increase in the maximum, observed thermodynamic deficit is seen shortly after tornado dissipation as the storm enters a non-tornadic cycle. Additionally, a convergent wind shift originating from prior convection is evident within the forward-flank of the storm prior to and during tornadogenesis. The evolution of these surface features will be presented along with dual-Doppler analysis from the SMART-R mobile radars to examine their possible role in the transition from a tornadic to a non-tornadic phase.