It is the influx of extremely strong cold air that is causing record heavy snowfall in various parts of Japan.
Regarding this factor, the Japan Meteorological Agency points out that in addition to the meandering of the "jet stream", a large-scale cyclone southward with cold Arctic air called the "polar vortex".
Since the middle of last month, extremely strong cold air has continued to flow in the vicinity of Japan due to the repeated strengthening of the winter-type pressure distribution, causing heavy snowfall in various places.
The Japan Meteorological Agency has pointed out the change in the positions of the "jet stream" and "polar vortex" as the cause of this cold air inflow.
Jet stream meanders south
A "polar front jet stream" and a "subtropical jet stream" are blowing from west to east near 12,000 meters above Japan.
Of these, the "polar front jet stream" located on the north side is affected by the high pressure developed in Siberia, and the "subtropical jet stream" located on the south side is affected by the active convective activity around Indonesia due to the La Nina phenomenon. , Both meander to the south.
This means that the strong cold air on the north side of the jet stream can easily flow in.
"Polar vortex" also goes south
What's more, a large cyclone called a "polar vortex" with cold Arctic air is moving southward.
This "polar vortex" is normally located in the northern part of the Sea of Okhotsk, but this season it has moved south to the south.
The meandering cold air of the "jet stream" and the cold air of the "polar vortex" from the south overlap in the vicinity of Japan, creating a very strong cold air that develops snow clouds in the Sea of Japan, resulting in record heavy snowfall. It is supposed to be.
The trend will continue
According to the Japan Meteorological Agency, this trend is expected to continue, and it is necessary to pay attention to heavy snowfall and severe cold weather.