北日本から西日本では、２０日も大気の状態が非常に不安定になり、雷を伴って非常に激しい雨が降るおそれがあるそうです。
A cold air mass at high altitudes and warm, damp air are causing extremely unstable atmospheric conditions in western and eastern Japan.
Heavy rain is expected to continue through Tuesday in some places. The Japan Meteorological Agency is urging people to be on the alert for mudslides, swollen rivers, and flooding in low-lying areas.
The agency says cold air is flowing in over Japan at high altitudes, and warm, damp air is also moving in, circling the edge of a high pressure system in the Pacific.
Forecasters say this is triggering extremely unstable conditions mainly on the Pacific coast of western and eastern Japan, and causing localized rain clouds to develop.
Rainfall of 66 millimeters per hour was observed in the hour to 6 p.m. on Monday, in the town of Tokigawa in Saitama Prefecture, near Tokyo.
A video posted to NHK's Scoop Box website shows flashes of lightning streaking across the sky from left to right in front of Higashi-Omiya station in Saitama City.
The woman who shot the video says she was surprised to see so much lightning. She says the rain started long before the loud rumbles of thunder, and it was very scary.
Through Tuesday, atmospheric conditions are likely to remain extremely unstable, mainly in western and eastern Japan. Extremely heavy thundershowers are forecast in some areas.
Forecasters are also calling on people to be alert for lightning strikes, tornadoes, gusts, and hail.
They say people should get to a safe place if they notice signs of developed cumulonimbus clouds approaching, such as sudden bursts of cold wind.
https://www3.nhk.or.jp/nhkworld/en/news/20240819_19/
本日取り上げるのは、cumulonimbus /ˌkjuː.mjə.loʊˈnɪm.bəs/（US） です。
『ジーニアス英和辞典』には「積乱雲」と記載されています。
OALD では "a high mass of thick cloud with a flat base, often seen during THUNDERSTORMS" と定義されています。
NHKニュースによると、雷の観測に力を入れている民間の気象会社「フランクリン・ジャパン」は、７月に関東の１都６県で、およそ７万２０００回の落雷が観測されたと発表したそうです。（emu）
https://www3.nhk.or.jp/news/html/20240820/k10014553951000.html
https://a30.hatenablog.com/entry/20130326/1364250923
https://a30.hatenablog.com/entry/20160622/1466584311
https://a30.hatenablog.com/entry/20171125/1511565770
https://a30.hatenablog.com/entry/20190126/1548476363
https://ameblo.jp/jyoji8/entry-12675777363.html
https://ameblo.jp/jyoji8/entry-12678631885.html