Temporal and vertical evolution of landfalling tornadoes over the Japan Sea area

Winter tornadic storms over the Japan Sea area have been observed during the Shonai Area Railroad Weather Project between 2007 and present. In this presentation, we will introduce winter tornadic storms during landfall over the Japan Sea area on January 25 2008 and 12 December 2009. The radar volume scans provide a unique dataset of vertical structures of a winter tornado on the sea and on land in the coastal region. The major features of the winter tornado during landfall are as follows. 1) The core radius was constant with height (i.e., upright cylinder). On the other hand, it does decrease the low-level on land (i.e., funnel shape). 2) The low-level vorticity increased dramatically on land; it is associated with the low-level contraction of the core radius. On the other hand, the low-level maximum tangential velocity was nearly constant in the vicinity of landfall. 3) There was no tilt of the vortex with height on the sea, while on land, there was a rearward-tilt with height. 4) The radar reflectivity images indicate that a well-defined hook echo on the sea. It was transformed to a more complicated shape on land. The tornado circulation had a spiral structure spiraling outward from the eye.