The heavy rain on the 25th of last month was caused by local fronts, etc.
On the 25th of last month, there was a record heavy rain in Chiba and Fukushima prefectures, and damage such as inundation and landslides continued. About the factor The Japan Meteorological Agency has analyzed that the rainfall has increased due to the impact of low air pressure and typhoon warm air and inland cold air, and local fronts.
On the 25th of the previous month, a week ago, it was a record heavy rain in Chiba and Fukushima prefectures where it would rain for the first month of October in just half a day.
According to the Japan Meteorological Agency, a low pressure approached ▽ Kanto on the 25th of last month, and Typhoon No. 21 was moving northeast off the east of Kanto.
For this reason, warm air from low pressure from the south continued to flow from the east and warm air from the east from Chiba Prefecture.
In addition, at that time, the inland of Kanto was cold due to the temperature falling due to the rain that preceded it.
By hitting this cold air with warm air from two directions due to low pressure and typhoon, a local front was generated, and it continued to stagnate near Chiba Prefecture, causing heavy rain.
After this, the cyclone began to move northward, but this time it approached the high pressure centered around the Kuril Islands and the pressure gradient increased, and in the Tohoku region such as Fukushima Prefecture, the east-side humid air continued to flow in. It is a heavy rain.
According to the Japan Meteorological Agency, the short rains caused by local fronts are likely to occur on the Pacific coast where wet air is likely to enter, but are difficult to predict accurately.
Naoji Nakamura, a forecaster at the Japan Meteorological Agency Forecasting Division, said, “The inland cold air is a very localized phenomenon, and it is difficult to predict the front. Forecasts may change from moment to moment. I want you to always check the latest weather information. "