The Development of Severe Vortices within Simulated High-Shear, Low-CAPE Convection

Details

• Journal Title:
  Monthly Weather Review
• Personal Author:
  Sherburn, Keith D. ; Parker, Matthew D.
• NOAA Program & Office:
  NWS (National Weather Service) ; OAR (Oceanic and Atmospheric Research)
• Description:
  Environments characterized by large values of vertical wind shear and modest convective available potential energy (CAPE) are colloquially referred to as high-shear, low-CAPE (HSLC) environments. Convection within these environments represents a considerable operational forecasting challenge. Generally, it has been determined that large low-level wind shear and steep low-level lapse rates—along with synoptic-scale forcing for ascent—are common ingredients supporting severe HSLC convection. This work studies the specific processes that lead to the development of strong surface vortices in HSLC convection, particularly associated with supercells embedded within a quasi-linear convective system (QLCS), and how these processes are affected by varying low-level shear vector magnitudes and lapse rates. Analysis of a control simulation, conducted with a base state similar to a typical HSLC severe environment, reveals that the key factors in the development of a strong surface vortex in HSLC embedded supercells are (i) a strong low- to midlevel mesocyclone, and (ii) a subsequent strong low-level updraft that results from the intense, upward-pointing dynamic perturbation pressure gradient acceleration. Through a matrix of high-resolution, idealized simulations, it is determined that sufficient low-level shear vector magnitudes are necessary for the development of low- to midlevel vertical vorticity factor (i), while steeper low-level lapse rates provide stronger initial low-level updrafts factor (ii). This work shows why increased low-level lapse rates and low-level shear vector magnitudes are important to HSLC convection on the storm scale, while also revealing similarities between surface vortexgenesis in HSLC embedded supercells and higher-CAPE supercells.
• Keywords:
  • Atmospheric Science
• Source:
  Monthly Weather Review, 147(6), 2189-2216
• DOI:
  https://doi.org/10.1175/mwr-d-18-0246.1
• ISSN:
  0027-0644 ; 1520-0493
• Format:
  PDF
• Publisher:
  American Meteorological Society
• Document Type:
  Journal Article
• Funding:
  Grant no. NA14NWS4680013 ; Grant no. NA15OAR4590235 ; Grant no. NA16OAR4590213
• Rights Information:
  Other
• Compliance:
  Library
• Download URL:
  https://repository.library.noaa.gov/view/noaa/60384/noaa_60384_DS1.pdf
• File Type:
  [PDF - 28.72 MB]
• Collection(s):
  Office of Oceanic and Atmospheric Research (OAR) ; National Weather Service (NWS)
• Main Document Checksum:
  urn:sha256:4cc58506cf2c8540170e918138c94d98317e73b99630efac1f42ac009d1f327f