The coming Japanese snow season 2021-2022

Sandy

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It's turned past the summer solstice and we can look forward to shorter days as we head towards the Japanese winter season.
Hopefully, unlike last season, Aussies CAN make it to Japan to hit the Japanese powder again after a one year hiatus.

What prompted me was the current Japanese weather.
It's the rainy season in Japan.... every year there is a stationary boundary that slowly moves north from south of Taiwan from about April, eventually hitting Japan in June, lasting around a month. In China, it's called the "Meiyu front", while in Japan it's the "Baiu" or "Tsuyu" front, but it means the same thing: Plum Rain, arriving in each place in time for the ripening of plums. Although it's the rainy season, it doesn't rain every day here in Yokohama (and Tokyo), so it's usually not too bad.

It arrives earlier in southern Japan, later in central Japan, and it tends to disperse when it gets too far north, tangled up with northerly cold fronts, so Hokkaido doesn't really have the "rainy season". It reappears briefly in September for about a week, moving quickly south. To the north of the stationary boundary, it's cooler and to the south, it's warmer, so after the Baiu Front passes, it clears and full summer hits Japan. In September, there is a sharp drop in temperatures after it passes south.

In 2018, it got tangled up with the remnant of a typhoon in southern Honshu, causing catastrophic floods. When it gets tangled in the strong circulation of a typhoon, the stationary boundary can get dragged slightly further south, staying put for a while over the same area, along with an additional injection of moisture

In the last few days, the Baiu Front has become tangled up in a tropical storm, skirting the area around Tokyo, and all along the Pacific coast 200km to the SW.

Here in Yokohama, we've had 319mm in the last 2 & 1/2 days. No thunderstorms, just consistent rain. Other places have fared worse....
Hakone, about 80km west of Yokohama has had 679mm in 2 & 1/2 days. Just a few hours ago, they had 105mm in 3 hours.

I will make occasional reports until the full winter snow season thread is appropriate, probably around November!!! ;)
 
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tot

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679mm in less than 3 days!
What sort of monthly averages are you talking for these places, given it does not rain for long?
 

Sandy

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Here in Yokohama, we've had 319mm in the last 2 & 1/2 days. No thunderstorms, just consistent rain. Other places have fared worse....
Hakone, about 80km west of Yokohama has had 679mm in 2 & 1/2 days. Just a few hours ago, they had 105mm in 3 hours.

20 people missing in Atami, not far from Hakone.

This is scary:

 
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Asama

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Very scary. Does a year ever go by without a severe rain disaster?
Last year was Kumagawa (Kumamoto) in the rainy season, 2019 had Typhoon No. 18 across central Honshu, 2018 was Kansai (or Hiromshima?) in the rainy season, 2017 was northern Kyushu in the rainy season, and that's just what I recall from the top of my head.
Volatile climate meets volatile geography?
 
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Sandy

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Very scary. Does a year ever go by without a severe rain disaster?
Last year was Kumagawa (Kumamoto) in the rainy season, 2019 had Typhoon No. 18 across central Honshu, 2018 was Kansai (or Hiromshima?) in the rainy season, 2017 was northern Kyushu in the rainy season, and that's just what I recall from the top of my head.
Volatile climate meets volatile geography?
Yes, 2018 was west of Hiroshima, northern Kyushu & Shikoku. That was also the year we got searing temperatures in June/July after the floods. I that case, it was the hook up with Typhoon Prapiroon with the Baiu Front, and this episode was also a storm remnant hooking up.
 

Sandy

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The rain stopped about 1pm today, but there's another depression currently east of the Korean peninsular, and that will move east, and inject more cloud into Japan.

The heavy rain and landslide alert is still in place until 3pm on Sunday. (In Yokohama)
 

skichanger

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Very scary. Does a year ever go by without a severe rain disaster?
Last year was Kumagawa (Kumamoto) in the rainy season, 2019 had Typhoon No. 18 across central Honshu, 2018 was Kansai (or Hiromshima?) in the rainy season, 2017 was northern Kyushu in the rainy season, and that's just what I recall from the top of my head.
Volatile climate meets volatile geography?
Have had several years with extreme rain. My personal experience
2016 ( I think) train track was cut between Myoko Kogen and Kurohime. A bit stressful when you are on your way to catch a flight. Also road out near Madarao
2018 Kansai airport flooded, Hokkaido earthquake and mudslides. We also had some mudslides on minor roads.
2019 typhoon Hagibis. Chikuma river banks broken. Shinkansen maintenance depot in Nagano flooded. Iiyama city centre underwater, Landslides causing road closures. Madarao ski slope needed some repairs. And unfortunately lives lost.
There was another time when the Keisei airport express was not running due to local floods.

And we think we have lots if natural disasters in Aus.
 
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Asama

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The rain stopped about 1pm today, but there's another depression currently east of the Korean peninsular, and that will move east, and inject more cloud into Japan.

The heavy rain and landslide alert is still in place until 3pm on Sunday. (In Yokohama)
The front must have formed a fairly narrow band hugging the coast. I'm 150km north of Atami and it was more or less sunny all day. Had no idea anything dramatic had happened until I looked at the news this evening.
 

Sandy

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The front must have formed a fairly narrow band hugging the coast. I'm 150km north of Atami and it was more or less sunny all day. Had no idea anything dramatic had happened until I looked at the news this evening.
It's a stationary boundary. As i mentioned, the boundary moves slowly north from around Taiwan over a couple of months.

2018-06-03: Cool air to the north, warmer air to the south. At that time, it was wet in southern China/HK.
2018-06-04 Rainy Season.png


Current:
2021-07-03: Stationary boundary along the Pacific coast of Honshu. That low to the east was originally a tropical depression south of Japan, which fed a lot of cloud into the Stationary boundary around Tokyo to Shizuoka.
20210703-08 Z surface analysis.png

That low west of the Korean penninsular will disrupt the Stationary boundary for a few days, and clear Kyushu & western Honshu of rain, from around Monday.


A few days back, the Stationary boundary was further to the south:
20210630-08 Z surface analysis.png
 
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Sandy

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Raining again this morning in Yokohama, but this time, it's associated with the low near Korean penninsular, so there's more rain on the Sea of Japan side. The rain is relatively light.
 
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Sandy

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Still a bit of rain around but the stationary boundary has moved further north now, rainy season may be ending.

The temperatures have risen, and this indicates to me that the warmer air south of the stationary boundary has arrived.....
Before the heavy rain last week, were were getting days of ~ 24-26 degrees (with rain every now and again), during the rainy days last week it was ~20, the next week has 29-30 degrees.


Stationary boundary further north:

20210706-15 Z surface analysis.png
 

Asama

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Nights have certainly become noticeably warmer in the last couple of days. Would be most grateful if rainy season doesn't drag on into August again. Last year it seemed to go on forever.
When you talk about the "stationary boundary", is that term interchangeable with the "baiu front"? The local weather forecast often talks about it moving north or south for a few days at a time.
 

Asama

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End of rainy season has been officially called for Kanto northwards. Some regions further south have yet to be called (weirdly).
Weather on the ground seems much the same as yesterday. Sunny morning, clouds brewing in the afternoon. Pleasant at 23C.
 
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Hyst

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I have desperately been searching for news on restrictions after most of the Japanese population has been vaccinated.
Anybody know what the intentions are? :cry_ubb:
(this must be the most important for us outside Japan - the others are just lucky bastards.) ;)
 
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Asama

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I have desperately been searching for news on restrictions after most of the Japanese population has been vaccinated.
Anybody know what the intentions are? :cry_ubb:
(this must be the most important for us outside Japan - the others are just lucky bastards.) ;)
Honestly, I have no idea. Sorry! Hoping my family may be able to visit some time next year, too.
 
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Hyst

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Asama

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Temperature records falling in Hokkaido today.

Asahikawa hit 36.2C (beating 36.0 in 1989), but more freakishly, the last 4 days (including today taking the #1 spot) will all have been amongst the top 10 hottest temperatures ever seen in Asahikawa.

1627381401643.png



Edit: Or not, one of those is from 1920. But there is another date from last week in the top 10.

Edit 2: Meanwhile thanks to typhoon, Karuizawa didn't even reach 20C today. Not complaining.
 
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Asama

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Temperature records falling in Hokkaido today.

Asahikawa hit 36.2C (beating 36.0 in 1989), but more freakishly, the last 4 days (including today taking the #1 spot) will all have been amongst the top 10 hottest temperatures ever seen in Asahikawa.

1627381401643.png



Edit: Or not, one of those is from 1920. But there is another date from last week in the top 10.

Edit 2: Meanwhile thanks to typhoon, Karuizawa didn't even reach 20C today. Not complaining.
Asahikawa has broken its own record again on consecutive days, by 0.5C.
36.7 at 2pm.

Shades of Canada last month...
 
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Sandy

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Nights have certainly become noticeably warmer in the last couple of days. Would be most grateful if rainy season doesn't drag on into August again. Last year it seemed to go on forever.
When you talk about the "stationary boundary", is that term interchangeable with the "baiu front"? The local weather forecast often talks about it moving north or south for a few days at a time.
The baiu front is what is observed from the ground over the years, but the meteorological cause is the stationary boundary. And that means you can see it in the weather map from months out.
 
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Nemps20

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The baiu front is what is observed from the ground over the years, but the meteorological cause is the stationary boundary. And that means you can see it in the weather map from months out.
Is there any correlation of a strong Baiu front leading to high winter snowfall?
Likewise for a weak Baiu front - low snowfall.
 

Asama

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Asahikawa has broken its own record again on consecutive days, by 0.5C.
36.7 at 2pm.

Shades of Canada last month...

Asahikawa... record broken again today! Topped out at 37.6C (so adding another 0.9C on top of the previous record).
35C was only reached 7 times in the 130 years from the start of records until last year.
This year it's been reached 7 times in 10 days.
What the hell's going on up there!?!
 
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Asama

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Asahikawa... record broken again today! Topped out at 37.6C (so adding another 0.9C on top of the previous record).
35C was only reached 7 times in the 130 years from the start of records until last year.
This year it's been reached 7 times in 10 days.
What the hell's going on up there!?!
Asahikawa record broken again!!! 37.9C.
Temps dropping over the coming days, so hopefully this will be the last time for the next 100 years... have a nasty feeling it won't though.
 
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Asama

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Now very chilly for August, and getting hammered with rain. Sure there will be news about flooding in Kyushu emerging over the next day or two.

Even here it's been raining for over 24hrs, mostly quite hard.

Just to illustrate the bonkers weather Hokkaido's been having, here's a temp graph for Wakkanai. A long spell of record breaking heat, followed by highs that failed to reach the average low. Chilly nights too. The plants and wildlife are going to be well confused...

1628944992995.png
 
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Asama

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Looks like a step down towards autumn weather is coming today/tomorrow.
This summer felt relatively cool to me. And it doesn't look like it will drag on into mid-September this year.
 
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Sandy

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Looks like a step down towards autumn weather is coming today/tomorrow.
This summer felt relatively cool to me. And it doesn't look like it will drag on into mid-September this year.
Yeah, a bit of rain coming, and cooler at night.

Stationary boundary(Baiu Front) is moving south according to the forecast:

20210901-21 JST surface forecast.png


The September transition is usually less than a week (while the June/July transition is 3-4 weeks for the rainy season)

To the south of the boundary is warm air, to the north is cooler air.
 
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Asama

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Yeah, a bit of rain coming, and cooler at night.

Stationary boundary(Baiu Front) is moving south according to the forecast:

20210901-21 JST surface forecast.png


The September transition is usually less than a week (while the June/July transition is 3-4 weeks for the rainy season)

To the south of the boundary is warm air, to the north is cooler air.
So the theory is that once this week's rain is out of the way, we shouldn't be seeing any rebound of summer heat?
 

Sandy

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Right now, the stationary boundary has moved off to the south of most parts of Japan. Temperatures have been cool during that period of around one week.

20210913-09 JST surface forecast.png


But right now the typhoon is directing warmer air across Japan from the south, while a cold front is cooling Hokkaido.

Nights have still been cooler however. Once the typhoon moves through, it will cool off to the mid 20s or a bit above in central Japan.


2021-09-13- 03 Korea.png
 

Sandy

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Typhoon Mindulle skirting Tokyo right now.

In Chiba Prefecture (east of Tokyo, across the bay) on the coast Katsuura, they have 126mm of rain in the last 4 hours.

Here in Yokohama, we've had 30mm in the last 2 hours. Steady rain, no thunderstorms and wind peaking at 84kph in the last hour.

2021-09-29 Satellite 0200 UTC.jpg


2021-10-01 Satellite 0330 UTC.jpg
 

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Not sure if anyone has noticed the snow on Asahidake, Hokkaido's highest mountain (2291 m). First snow this autumn?
Asahidake_20211006.jpg
 

Sandy

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There was a particularly cool period in mid August (mainly due to days of rain), but the last days of September and the first 5 days of October have been warmer than usual.
Hopefully we get the early autumn step change in the next week.
 

Sandy

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FINALLY, after an extra warm first 10 days of October (Av 27.5C max in Tokyo, 26.2 in Nagano City, and even Sapporo 21.1), it looks like the first part of autumn will finally come to Japan.

Next 7 days in Yokohama expecting:
- Highs of 22,21,24,26,26,21,19,
- Lows of 21,18,18,19,19,16,14
 
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Sandy

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Next 7 days in Yokohama expecting:
- Highs of 17,19,16,21,20,19,20,
- Lows of 16,13,11,14,12,11,13


And it's dipped down to 13.9C just before 1pm
 
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