TOKYO - Although the winter weather pattern is easing today on November 19th, bringing clear skies to some regions, forecasters warn that coastal areas may still face sudden bursts of rain, snow, and severe convection driven by rapidly developing thunderclouds.
Meteorologists note that when the winter pattern weakens, inland areas cool sharply due to radiative cooling, allowing a mesoscale high-pressure system to form. Southerly winds generated from this high pressure can collide with the lingering northwesterly flow over the Sea of Japan, creating a shear line that increases the likelihood of thundercloud development along coastal zones. As a result, residents in these areas — rather than in the mountains — are urged to watch for lightning, hail, sudden downpours, and strong gusts.
Rain and snow are expected across four broad regions. On the Sea of Japan side from Hokuriku to southern Tohoku, lingering cold air will maintain a mix of rain and snow. Around the Izu Islands, the shear line associated with the so-called “ninja cloud” that brought rain to Tokyo yesterday will continue to generate showers. In the San’in region, rain is forecast as the JPCZ — the Japan Sea Polar Air Mass Convergence Zone — forms another shear line, with additional caution advised along the Kii Channel. From western Kyushu across southern waters, a northwesterly–southeasterly shear line is likely to produce widespread rain through the day, particularly around the Goto Islands, Tanegashima, and Yakushima. Okinawa will remain susceptible to rain clouds associated with a nearby front.
The most severe conditions are expected along coastal areas from Hokuriku to southern Tohoku, including regions such as Joetsu in Niigata Prefecture, Akita City, and the Oga Peninsula. Mature thunderclouds could approach suddenly, bringing abrupt lightning, hail, and intense wind gusts.
Weather agencies urge residents to stay alert to real-time radar and cloud movement throughout the day and to check the latest forecasts using weather apps and official platforms.
Source: ウェザーニュース
