Details:

Journal Title:
Weather and Forecasting
Personal Author:
Koch, Steven E. ; Ware, Randolph ; Jiang, Hongli ; Xie, Yuanfu
Koch, Steven E. ; Ware, Randolph ; Jiang, Hongli ; Xie, Yuanfu Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory) ; NSSL (National Severe Storms Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences)
OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory) ; NSSL (National Severe Storms Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences) Less -
Description:
This study documents a very rapid increase in convective instability, vertical wind shear, and mesoscale forcing for ascent leading to the formation of a highly unusual tornado as detected by a ground-based microwave radiometer and wind profiler, and in 1-km resolution mesoanalyses. Mesoscale forcing for the rapid development of severe convection began with the arrival of a strong upper-level jet streak with pronounced divergence in its left exit region and associated intensification of the low-level flow to the south of a pronounced warm front. The resultant increase in stretching deformation along the front occurred in association with warming immediately to its south as low-level clouds dissipated. This created a narrow ribbon of intense frontogenesis and a rapid increase in convective available potential energy (CAPE) within 75 min of tornadogenesis. The Windsor, Colorado, storm formed at the juncture of this warm frontogenesis zone and a developing dryline. Storm-relative helicity suddenly increased to large values during this pretornadic period as a midtropospheric layer of strong southeasterly winds descended to low levels. The following events also occurred simultaneously within this short period of time: a pronounced decrease in midtropospheric equivalent potential temperature theta(e) accompanying the descending jet, an increase in low-level theta(e) associated with the surface sensible heating, and elimination of the capping inversion and convective inhibition. The simultaneous nature of these rapid changes over such a short period of time, not fully captured in Storm Prediction Center mesoanalyses, was likely critical in generating this unusual tornadic event.
Source:
Weather and Forecasting, 31(3), 763-786.
DOI:
https://doi.org/10.1175/WAF-D-15-0105.1
Document Type:
Journal Article
Rights Information:
Other
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:9edab8be212d07c4a262bcee6447d1fb16ade772354acfc5cb5fa54f6f07ea5d
Download URL:
https://repository.library.noaa.gov/view/noaa/16492/noaa_16492_DS1.pdf
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