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Abstract Supercells in landfalling tropical cyclones (TCs) often produce tornadoes that can cause fatalities and extensive damage. In previous studies, many tornadoes have been shown to form <50 km from the coast, and their parent storms may also intensify as they cross the coastal boundary. This study uses WSR‐88D observations of TC tornadic mesocyclones from 2011 to 2018 to examine changes in their low‐level rotation upon moving onshore. We will show that radar‐derived azimuthal shear tends to increase in storms that cross the coastal boundary. Similar intensification trends are also found in radar‐derived (supercell) storm‐scale divergence, such that storm‐scale convergence increases as storms move onshore. It is likely changes in the near‐coast vertical wind shear and/or near‐shore convergence helps explain supercell intensification, which is important to consider particularly in operational settings.
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Examining Outer Band Supercell Environments in Landfalling Tropical Cyclones Using Ground-Based Radar Analyses
Abstract Supercells in landfalling tropical cyclones (TCs) often produce tornadoes within 50 km of the coastline. The prevalence of TC tornadoes near the coast is not explained by the synoptic environments of the TC, suggesting a mesoscale influence is likely. Past case studies point to thermodynamic contrasts between ocean and land or convergence along the coast as a possible mechanism for enhancing supercell mesocyclones and storm intensity. This study augments past work by examining the changes in the hurricane boundary layer over land in the context of vertical wind shear. Using ground-based single- and dual-Doppler radar analyses, we show that the reduction in the boundary layer wind results in an increase in vertical wind shear/storm-relative helicity inland of the coast. We also show that convergence along the coast may be impactful to supercells as they cross the coastal boundary. Finally, we briefly document the changes in mesocyclone vertical vorticity to assess how the environmental changes may impact individual supercells.
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- Award ID(s):
- 2028151
- PAR ID:
- 10545811
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Monthly Weather Review
- Volume:
- 152
- Issue:
- 10
- ISSN:
- 0027-0644
- Format(s):
- Medium: X Size: p. 2265-2285
- Size(s):
- p. 2265-2285
- Sponsoring Org:
- National Science Foundation
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