Precipitation Processes and Vortex Alignment during the Intensification of a Weak Tropical Cyclone in Moderate Vertical Shear

Details

• Journal Title:
  Monthly Weather Review
• Personal Author:
  Rogers, Robert F. ; Reasor, Paul D. ; Zawislak, Jonathan A. ; Nguyen, Leon T.
• NOAA Program & Office:
  CIMAS (Cooperative Institute for Marine and Atmospheric Studies) ; OAR (Oceanic and Atmospheric Research) ; AOML (Atlantic Oceanographic and Meteorological Laboratory)
• Description:
  The mechanisms underlying the development of a deep, aligned vortex, and the role of convection and vertical shear in this process, are explored by examining airborne Doppler radar and deep-layer dropsonde observations of the intensification of Hurricane Hermine (2016), a long-lived tropical depression that intensified to hurricane strength in the presence of moderate vertical wind shear. During Hermine’s intensification the low-level circulation appeared to shift toward locations of deep convection that occurred primarily downshear. Hermine began to steadily intensify once a compact low-level vortex developed within a region of deep convection in close proximity to a midlevel circulation, causing vorticity to amplify in the lower troposphere primarily through stretching and tilting from the deep convection. A notable transition of the vertical mass flux profile downshear of the low-level vortex to a bottom-heavy profile also occurred at this time. The transition in the mass flux profile was associated with more widespread moderate convection and a change in the structure of the deep convection to a bottom-heavy mass flux profile, resulting in greater stretching of vorticity in the lower troposphere of the downshear environment. These structural changes in the convection were related to a moistening in the midtroposphere downshear, a stabilization in the lower troposphere, and the development of a mid- to upper-level warm anomaly associated with the developing midlevel circulation. The evolution of precipitation structure shown here suggests a multiscale cooperative interaction across the convective and mesoscale that facilitates an aligned vortex that persists beyond convective time scales, allowing Hermine to steadily intensify to hurricane strength.
• Keywords:
  Cyclones—Tropics
• Source:
  Monthly Weather Review, 148 (5)
• DOI:
  https://doi.org/10.1175/MWR-D-19-0315.1
• Document Type:
  Journal Article
• Rights Information:
  Other
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:00c5d6244f1776158759bb91eb67bf1cec0913cba0fd97c541aea0e8b89be3d91fae15e06cb4f8e4fd70bc150b49df740df62c5bce4f7ae94a751fa4ecb4a049
• Download URL:
  https://repository.library.noaa.gov/view/noaa/26357/noaa_26357_DS1.pdf
• File Type:
  [PDF - 7.66 MB ]