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Background Material

Bounded Weak Echo Region (BWER)Supercell motion has remained an interesting topic since the 1940s when the documentation of these storms was in its infancy. The feature that sets supercells apart from ordinary thunderstorms is the presence of deep and persistent rotation (counterclockwise for right-moving storms and clockwise for left-moving storms, irrespective of hemisphere). Note that right-/left-moving is relative to the hodograph (i.e., shear). This rotation induces a propagation component that is at right angles to the vertical wind shear (and not the mean wind). This sometimes leads to a supercell motion that is at significant angles to the mean wind, and in a few instances, supercells have been observed to move "upstream" against the mean flow.  As a result of these observations, and along with inspiration from the COMET module, "Anticipating Convective Storm Structure and Evolution," we began research in 1996 to further study the behavior of supercell motion, with a goal of being able to better predict supercell motion prior to storm formation. Our results support many of the previous theoretical and modeling studies, which indicate that supercell motion is primarily determined by advection plus rotationally induced propagation across the vertical wind shear. Studies by Ramsay and Doswell (2005) and Thomson et al. (2007) have supported our work. We also note that thermodynamics may play a noteworthy role in modulating supercell motion on occasion, and recent modeling work sheds some light on this topic (Kirkpatrick et al. 2007). After completing the above storm motion project, we looked at the vertical wind shear in environments of both right- and left-moving supercells (Bunkers 2002). We found that the bulk and total wind shear are similar for the two classes, but the absolute value of storm-relative helicity is larger for right-moving supercells, relative to the left-movers, across the United States.

Contact: If you have questions or comments about supercell motion, supercell longevity, or any of the other references listed on this page, please e-mail Matthew Bunkers, the Science and Operations Officer at the National Weather Service (NWS) in Rapid City, SD.

Hodographs & 2005 Virtual Institute for Satellite Integration Training (VISIT) Teletraining

a)  Hodograph (with SRH contours)
b)  Hodograph (with storm-relative winds)
c)  Hodograph (with 250-m spacing)
d)  Supercell Motion Teletraining (includes audio playback version)
e)  Predicting Supercell Motion in Operations (standalone PPT)

Formal Publications

Informal Publications