14A.4 An Examination of the 20 June 2015 Convective Initiation Event during PECAN

Thursday, 10 November 2016: 11:15 AM
Pavilion Ballroom East (Hilton Portland )
Brianna Marlene Lund, University of Alabama-Huntsville, Huntsville, AL; and K. R. Knupp

The timing and location of convective initiation (CI) represents a continued and important focus of severe weather phenomena. The poorly understood catalysts for CI motivate questions surrounding the timing, location and physical processes of CI, particularly during the Afternoon-Evening Transition (AET). During the summer of 2015, the Plains Elevated Convection at Night (PECAN) field campaign took place to study nocturnal convection amongst a number of other phenomena. One of the objectives of PECAN was to examine the phenomenon of CI during the AET. During the late afternoon to early evening hours on 20 June 2015, a CI mission was conducted near Hays, KS. Initiation was observed along a weak cold front and was captured by multiple instruments, including the Mobile Integrated Profiling System (MIPS), the S-Pol radar, and two other fixed profiling sites. All UAH-based mobile assets were deployed for this mission and data from those instruments will be considered most heavily, in particular, the MIPS X-band Profiling Radar, the Multi-Channel Profiling Radiometer, the 915 MHz Wind Profiler, and the Doppler Wind Lidar (DWL). The present hypothesis of this study is that a closer investigation of the finer scale features found during the AET of the boundary layer may shed light on the evolution of microscale mechanisms initiating convection, such as a reduction in turbulence and turbulent momentum fluxes, and a subsequent increase in boundary layer convergence. In this case, deep convective clouds rapidly developed along the cold front during the AET as the cold front passed over the MIPS. Preliminary observations illustrate significant upward vertical motion sustained for approximately 15 minutes, and an increase in the depth of water vapor. A characteristically turbulent boundary layer preceded initiation, and an unusually turbulent ABL persisted into the early nocturnal boundary layer cycle after CI had occurred. A number of boundaries and linear features were also present and observed by the S-Pol radar and other mobile assets, making this a very complicated and unique case for study.
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