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Abstract

On the early February 2018, a cold surge struck the Japanese Islands and brought the Japan sea polar air mass convergence zone (JPCZ). The edge of JPCZ stayed at Hokuriku district of Japan, and gave a heavy snow. On the same time, a polar meso cyclone (PMC) also stayed over the Japan Sea west of Hokkaido. Despite that this simultaneous event of JPCZ and PMCs have been observed many times, their interaction remains unclear. And, since PMCs rarely move northward, such mechanisms also are yet fully understood. In this study, by examining synoptic environments, we investigate physical backgroungs of the northward movement of the polar meso cyclone mentioned above and discuss its linkage to the JPCZ. We used data of the Meso-scale Model provided by Japan Meteorological Agency. During the PMC was moving northward, convections were observed over the north side of the PMC and their latent heating could pull the low center northward. The convections could be enhanced by warm and humid air transported from an extratropical cyclone over the Pacific. While the PMC moved northward, the upper level cold air moved southward. Thus, the PMC left from the baroclinic zone, became slow under weak upper level winds, and eventually stopped moving due to the surfase monsoonal northerly wind. We would like to show the results for other simultaneous events of JPCZ and PMCs which were observed during January to February 2018.