The Association of Strong Near-Surface Wind Shear Profiles with Enhanced Probabilities of Significant Severe Weather and Tornado Events.
type: CreativeWork
description: On several significant tornado days, a distinct combination of near surface (< 1 km AGL) speed and directional shear has been noted in pre-tornadic vertical wind profiles. This combination consists of intense speed shear followed by intense directional shear between the surface and 1 km AGL, which appears as a sickle-shape on a hodograph. A composite sickle-shaped hodograph was constructed using several notable tornado outbreak days. The composite hodograph was used to examine the historical upper-air database for the 1995-2004 period in order to determine the relative frequency of the sickle-shape. Furthermore, the occurrence of the sickle-shape was related to severe weather documented within spatial and temporal proximity of the sounding site. Over the 10-year dataset, the sickle-shape was found to occur at most 4% of the time. It was also found that the sickle-shape occurs less than 0.5% of the time in the presence of minimally supportive kinematics and thermodynamics. On those days when the sickle-shape was accompanied by minimally supportive kinematics and thermodynamics (0-6 km AGL shear ≥ 20 m s-1 and CAPE ≥ 500 J kg-1), it was found that severe weather and tornadoes were more likely to be observed in proximity to the sounding site. The results show that the presence of the sickle-shaped hodograph and minimally supportive thermodynamics and kinematics is related to an increased likelihood of tornadic and significantly tornadic events.
abstract: On several significant tornado days, a distinct combination of near surface (< 1 km AGL) speed and directional shear has been noted in pre-tornadic vertical wind profiles. This combination consists of intense speed shear followed by intense directional shear between the surface and 1 km AGL, which appears as a sickle-shape on a hodograph. A composite sickle-shaped hodograph was constructed using several notable tornado outbreak days. The composite hodograph was used to examine the historical upper-air database for the 1995-2004 period in order to determine the relative frequency of the sickle-shape. Furthermore, the occurrence of the sickle-shape was related to severe weather documented within spatial and temporal proximity of the sounding site. Over the 10-year dataset, the sickle-shape was found to occur at most 4% of the time. It was also found that the sickle-shape occurs less than 0.5% of the time in the presence of minimally supportive kinematics and thermodynamics. On those days when the sickle-shape was accompanied by minimally supportive kinematics and thermodynamics (0-6 km AGL shear ≥ 20 m s-1 and CAPE ≥ 500 J kg-1), it was found that severe weather and tornadoes were more likely to be observed in proximity to the sounding site. The results show that the presence of the sickle-shaped hodograph and minimally supportive thermodynamics and kinematics is related to an increased likelihood of tornadic and significantly tornadic events.
author: Ludwig, Stephanie L.
language: en_US
date published: 2010-05-03
date modified: 2026-07-24T01:50:02Z
provider: Creighton University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Creighton University

PropertyValue
property ID: Handle
value: http://hdl.handle.net/10504/6118