South Florida Sea Breeze Tornadoes: A Look Into Non-Supercell Tornadogenesis

1. South Florida Sea Breeze Tornadoes
A Look Into Non-Supercell Tornadogenesis
James Duncan
Department of Earth, Ocean, and Atmospheric Science
Florida State University
Introduction Analysis Juno & Riviera
Conclusion
In terms of annual tornado mean density, the Beach Tornadoes
•Sea Breeze Progression
state of Florida ranks number one across the Tornadogenesis by definition requires the
1402 Z 1702 Z 2032 Z 2115 Z 2215 Z 2302 Z
entire United States. Despite this, the majority of presence of large values of vertical vorticity
these tornadoes of are non-supercell origins. near the ground.
On August 7, 2003, two tornadoes (landspouts) Within supercells, these values of vertical
of magnitude F0 and F1 (nearly F2) spawned vorticity are an enhanced byproduct of
across portions of urban Palm Beach County. stretching and tilting associated with up and
downdrafts of the supercell. Non-supercell
Primary Objectives tornadogenesis is unique in that it does not
require the presence of a downdraft.
•What conditions are needed for non-supercell
This case study serves to illustrate that the
tornadogenesis?
collision of air-mass boundaries, in this
•Given a certain synoptic environment, illustrate
•Vertically Integrated Liquid (VIL) Imagery instance the sea breeze and the outflow
how the the collision of certain air mass
2117 Z 2129 Z 2158 Z boundary from a neighboring thunderstorm,
boundaries (sea breeze) serve to generate non-
can supply sufficient values of vertical
supercell tornadoes.
vorticity for tornadogenesis. Furthermore,
the weak shear environment of the South
Synoptic Setup Florida summer maximizes the time with
which updrafts (further enhanced my the
collision) may remain over these areas of
•Storm Relative Velocity (SRV) Imagery vertical vorticity.
2117 Z 2123 Z 2129 Z 2135 Z
References
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Collins, J. M., C. H. Paxton, and A. N. Williams, 2009: Precursors to southwest
•Subtropical Ridge extending across central South Florida warm season tornado development. Electronic J. Operational Meteor.,
Florida (atypical prevailing southwesterly flow). 12, 1-31.
GOES-12 Archive, 2012: goes.gsfc.nasa.gov/text/goes12results.html.
•Low Environmental Shear but Large Instability HPC’s Surface Analysis Archive, 2012:
www.hpc.ncep.noaa.gov/html/sfc_archive.html.
NCDC, 2012: http://www4.ncdc.noaa.gov/oa/radar/radardata.html.
Pfost, R. L., P. Santos, and T. E. Warner, 2005: South Florida
seabreeze/outflow boundary tornadoes. Electronic J. Operational Meteor., 6,
1-20.
University of Wyoming, Atmospheric Soundings, 2012:
http://weather.uwyo.edu.edu/upperair/sounding.html.