18.4 Observed Low-level Cloud Morphology Associated with Tornadogenesis Events During the Southeastern United States Cool Season

Friday, 11 November 2016: 11:15 AM
Pavilion Ballroom (Hilton Portland )
Christopher A. Lisauckis, Univ. of Alabama, Huntsville, AL; and K. R. Knupp

Handout (1.1 MB)

It has been observed that tornadogenesis within the southeastern United States often occurs within a wider range of conditions than observed in other regions. Specifically, the cool season presents challenges to tornado forecasting due to high shear and low CAPE (HSLC) conditions.  Values of CAPE are particularly challenging to estimate due to paucity of soundings, potential differences between the LCL and actual cloud base (Craven et al. 2002), and inadequate parameterization of boundary layer (BL) processes by forecast models (Cohen et al. 2015). We hypothesize that low level clouds (stratocumulus in particular) play an important role in controlling the BL processes during cold season tornado events. In this paper, we analyze lidar ceilometer, Doppler wind lidar, 915 MHz wind profiler, microwave profiling radiometer, C-band dual polarization radar, and available balloon sounding observations to more fully characterize low level cloud evolution (e.g., cloud base height, cloud fraction) and associated BL profiles of wind, turbulence (e.g., variance of vertical motion), water vapor, and BL cloud depth in close proximity to tornadogenesis events over northern Alabama and other locations in the Southeast. Of particular interest is to further explore the relationship between cloud base height and LCL height for this cool season HSLC environment for both diurnal and nocturnal conditions. Observed evolution of storm relative inflow and helicity in the 0-1 km layer, as well as low level moisture depth and relative humidity characteristics are also of interest.
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