Extended Abstract (120K)8A.6a
Doppler Radar Observation of Winter Tornadoes over the Japan Sea (Formerly paper number, P4a.7)
Fumiaki Kobayashi, National Defense Academy, Yokosuka, Japan
Tornadoes (supercell tornadoes, landspouts and water spouts) often occur in Japan. About 20 tornadoes per year occurred on the average in Japan. According to the geographical distribution, many tornadoes occurred along the coastline of the Pacific Ocean. On the other hand, tornadoes also reported on the Japan Sea coast in winter. Ishikawa Prefecture is the highest value of "the tornado probability" which is larger than that of several Prefectures on the Pacific side. Supercell tornadoes often occurred in Japan. However, the structure, morphology or mechanism of the tornadoes, which occurred over the Japan Sea in winter, is unknown until now. We call the tornadoes generated over the Japan Sea in winter season as "tornadoes with snowcloud" or "winter tornadoes". In this paper, we would introduce case studies of winter tornadoes observed at the Hokuriku coast. Doppler radar observation was carried out from the middle of December to the end of January for recent five years at the Hokuriku coast. In specially, the observation project of "Winter MCSs Observations over the Japan Sea (WMO)" was carried out using Doppler radars, GPS sondes, and wind profilers and so on in January from 2001 to 2003. We would show the structure and characteristic features of winter tornadoes, which occurred close to the radar site in the special observation period and variety of winter tornadoes. Some tornadoes were non-supercell tornadoes formed under the winter monsoon. F0`F2 tornadoes were accompanied with a misocyclone (`1km diameter) near the cloud base and single funnel cloud. The mechanism of the tornado formation was guessed that the horizontal wind shear near the surface or the vertical wind shear of sub-cloud layer made the vertical vortex like "non-supercell" tornadoes. On the other hand, "mini-supercell" like F3 tornado accompanied with a mesocyclone (10km diameter) also observed, which caused damage to more than 200 houses. The tornado was associated with a hook echo (mesocyclone) which developed near the center of a mesoscale (100km diameter) vortex over the Japan Sea. These observation results indicate a possibility of so many "winter tornadoes" generation over the Japan Sea.
Session 8A, Severe Weather II
Sunday, 10 August 2003, 10:30 AM-12:30 PM
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