News From Christmas night to the end of the year Cold wave invasion What is JPCZ that brings the strongest class heavy snow ever?

Image: tenki.jp

From now on, the year-end cold wave will hit from the night of Christmas on the 25th. The strongest this season and the strongest level ever for December. There is also a risk of heavy snow, especially on the Sea of ​​Japan side. What is JPCZ, which is a major cause?

Cause of Doka Snow

Image: tenki.jp

The other day, from December 17th (Friday) to 18th (Saturday), it became a heavy snowfall with more than 50 cm of snowfall overnight, mainly on the Sea of ​​Japan side such as Hokuriku. The cause is that the winter-type pressure distribution became stronger and strong cold air flowed in, and the Japan Sea Polar Air Mass Convergence Zone called JPCZ was formed. When the winter-type pressure distribution becomes stronger, cold wind (cold air) flows into the Sea of ​​Japan from the Siberian continent. This cold wind (cold air) is divided into two by the Changbai Mountains (highest peak: Mt. Baekdu 2744 meters) near the boundary between China and the Korean Peninsula, and then collides again downwind (Sea of ​​Japan) to create a convergence zone (a line where snow clouds tend to develop). ) Is formed, and snow clouds are likely to develop.

This winter

Image: tenki.jp

Another cause of heavy snowfall is the high surface temperature of the Sea of ​​Japan this winter. The cold, dry air (cold air) coming from the continent replenishes plenty of water vapor in the Sea of ​​Japan and grows into snow clouds. At that time, if the sea surface temperature of the Sea of ​​Japan is high, snow clouds will develop and heavy snow will fall in order to obtain more water vapor. In October and November of this year, the sea surface temperature of the Sea of ​​Japan was the highest since 1982. Even now (December), the Sea of ​​Japan is about 15 degrees Celsius, which is about 3 degrees Celsius higher than normal, making it a place where cumulonimbus clouds are likely to develop.

Watchful weather charts and the strongest levels of chills

Image: tenki.jp

The important weather map is when the isobars are dented like the other day (17th to 18th). Please note that JPCZ is likely to be formed. The forecast weather map for December 25 is also a forecast that the isobars will be dented (yellow dotted line) in the Sea of ​​Japan. Also, from Christmas night on the 25th, it is expected that a winter general (chills) will invade around western Japan. It is a cold wave that is stronger than the 17th to the 18th, and the cold air that is record strong for December continues for a long time. The cold air (below -6 ° C at around 1500 meters above the sky), which is a guideline for snow if it falls on the ground, completely covers western Japan on the 25th and Honshu from the 26th to the 27th. The temperature of 1500 meters above the sky is expected to be -15.7 ℃ at 9 o'clock on the 26th in Fukuoka (the past 1st place in December was -15.3 ℃), which is about 13 ℃ lower than normal and is expected to renew the past 1st place. Tateno (Tsukuba) is expected to reach -12.3 ℃ at 21:00 on the 26th (the past 1st place in December was -11.7 ℃), which is about 11 ℃ lower than normal and will renew the past 1st place. Wajima is expected to renew the past 1st place at 9:00 on the 26th with -14.4 ℃ (the past 1st place in December was -14.2 ℃). In addition, it is expected that cold air of -40 ° C or less will flow into northern Japan such as Sapporo and Akita, and minus 37 ° C or less will flow into Hokuriku such as Wajima near 5000 meters above the sky, which is higher than 1500 meters. Around 5,000 meters above the sky, minus 36 degrees Celsius or less is considered to be a guideline for heavy snowfall, so you can see how strong it is. There is a risk of record heavy snowfall towards the end of the year. Check the weather information and traffic information diligently, and be prepared for any accidents such as a car getting stuck.

Japan Weather Association Headquarters Fukutomi