The
Structure, Evolution, and Dynamics of a Nocturnal Convective System
Simulated Using the WRF-ARW Model
Ben Blake
EMC
Noon Mar 29 in Room 2155
Abstract:
Previous studies have documented a nocturnal maximum in thunderstorm
frequency across the central United States. Forecast skill for
nocturnal convection remains relatively low, and the explanation for
this nocturnal maximum is still an area of active debate. This study
utilized the WRF-ARW model Version 3.6.1 to simulate a nocturnal
mesoscale convective system event that occurred over the southern Great
Plains on 3-4 June 2013. The purpose of this study was to advance the
knowledge of the dynamics, structure, and evolution of nocturnal
convection through examining the structure of the simulated storm from
the perspective of two dynamical frameworks.
The structure and evolution of the storm was influenced by a strong
horizontal gradient in CAPE and CIN corresponding to a narrow corridor
of high mixing ratios associated with the low-level jet. These CAPE
values in the jet exceeded the magnitude of CAPE observed in the
daytime boundary layer. During the night, the source of convectively
unstable parcels was almost entirely above 1 km, the storm was elevated
with positive buoyancy limited to heights above ~4 km, and the cold
pool became stronger aloft than at the surface. Significant variation
in the depth and structure of the ascent was found around the cold
pool. The reasons for this variation are examined via two frameworks:
i) The RKW framework for vertical shear/cold pool interactions; ii) The
dynamical framework of wave theory (e.g. Froude number, Scorer
parameter). The application of these theories allowed insight into the
three-dimensional structure of the convective system and provided a
possible explanation for how convection is maintained at night in the
presence of a low-level jet.