Tutorial Snow forecasting tutorial for Japan

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
Ok, here's the NEXT installment of the terrain map snow guide for central Japan. Strangely enough, I only seem to get time to do this when the Xmas holidays roll around!!!! ;)

This shows the approx locations of the major resort areas of northern Nagano and Niigata.
NaganoNiigata.jpg


Myoko 2.jpg


Things to note:
- Myoko, Nozawa & Yuzawa seem to cop the biggest snow of those areas, along with Cortina, which is more exposed to the wind than the other Hakuba resorts.
- Some conventional wisdom says that the resorts closest to the sea get more snow. However, this is not the whole story. For example, Yuzawa is further from the sea but gets a lot of snow.

More to follow.....
 
Last edited:

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
Ok, analysis:

NozawaYuzawaSKwind.jpg


The key for Nozawa & Yuzawa is the ridge line I've indicated. I watched from the top of Nozawa, a bit of cloud pushing in from the north, hitting the ridge line, and seeing great blobs of cloud form right as you watch. This thicker cloud then pushes across Nozawa and further inland to Yuzawa. Since the ridge line is curved, almost like a focus on Nozawa, Nozawa can get big snow from a number of directions. Yuzawa's directions are a bit more specific.

Yasuzuka to the north of Nozawa, at 126m often gets a lot of snow when the winds are lighter and the cloud is unable to push over the mountains from the coastal plain. It's a good indicator for wind direction and snow amount to hit Nozawa & Yuzawa when the wind picks up later on.

Shiga Kogen has limited wind directions, with NW crossing a gap. NNW is best as the cloud thickens on the ridge and skirt to the west of Nozawa.
 
Last edited:
  • Like
Reactions: Pat42

nickGT

Early Days
Jun 2, 2015
129
15
18
Thanks for taking the time to post all this info Sandy.

Looking forward to seeing a bit more detail around Myoko & Madarao.
 

DPS Driver

A Local
Jul 18, 2014
5,605
6,589
563
Probably worth mentioning that if you get any south in the wind beware of skiing loaded slopes lea to the w s/w. Snow from that direction tends to be heavy and wet and is prone to slab formation.
Sandy's explanations previous re the best wind direction for the good snow, might help some better understand the conditions which lead to a sketchy snowpack.
 

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
http://www.tropicaltidbits.com/anal...cpn&runtime=2016112506&fh=360&xpos=0&ypos=228

On thing about the GFS is that they seem to have two different running models: 00z & 12z, and the 06z & 18z
So if you look at the next 6 hours, you might see an upgrade or a down grade, but what you are seeing is the two different model runs.

So for example the 00z Nov 25 2016, for 00z Dec 09:

gfs_mslp_pcpn_wpac_48.png


06z Nov 25 2016, for 18z Dec 09:
gfs_mslp_pcpn_wpac_49.png



00z Nov 25 2016, for 12z Dec 09:

gfs_mslp_pcpn_wpac_49.png


06z Nov 25 2016, for 06z Dec 10:

gfs_mslp_pcpn_wpac_50.png


These are SUPPOSED to be sequential, 6 hour increments.
The 2nd & 4th have a deep low east of Hokkaido, while the 1st & 3rd don't.

So the 1st & 3rd are one model run, while the 2nd & 4th are a DIFFERENT run. THIS is why it looks like there are 6 hourly "upgrades: and "downgrades". Each run uses as the input, the output from the previous 12 hours. So you have two runs which are different.
When the two models converge (usually about 5 days out), you have a reasonably good forecast. You tend to find that when the two runs are VERY SIMILAR a long way out, then it's more likely to be right.
 

Crispy013

One of Us
Jun 6, 2010
2,005
2,772
363
Port Macquarie, NSW
Is there any indication as to which is more likely to be better at predicting the most accurate forecast for Japan?

Like, is there a greater probability that the 00z/12z models are more reliable? Or does a certain run predict better if it is a certain 'type' of system?
 

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
Is there any indication as to which is more likely to be better at predicting the most accurate forecast for Japan?

Like, is there a greater probability that the 00z/12z models are more reliable? Or does a certain run predict better if it is a certain 'type' of system?

TBH, I'm not sure.... but that will give me a project before the season starts proper!!!! ;)
 

Jellybeans

Part of the Furniture
Ski Pass
Aug 24, 2015
13,056
21,539
813
Canberra
Is there any indication as to which is more likely to be better at predicting the most accurate forecast for Japan?

Like, is there a greater probability that the 00z/12z models are more reliable? Or does a certain run predict better if it is a certain 'type' of system?
00Z - Weather buoy, satellite data, shipping data, country data, NOAA data
06Z - Weather buoy, satellite data, shipping data
12Z - Shipping data, Satellite data ONLY
18Z - Weather buoy, satellite data, shipping data, country data, NOAA data
This apples to all the major models. These are the datasets used to make the forecasts
0Z and 18Z use the most data sources, so are usually the most accurate.
 
  • Like
Reactions: Born2ski

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
(from the 2016/17 Japan thread)
There's been a few questions about the lake/sea effect. e.g. "Winds are from the north, why is there no lake effect?" or "Isobars are close, why no lake effect?", or "there's a lot of lake effect cloud, why isn't it snowing?" etc.

Here is more explanation for central Japan.
1. Optimal. Strong NNW wind. Long fetch from Siberia. Better inland penetration, as it's more perpendicular to the coast. Low temperatures with maximum temperature differential from air to sea.
2. Very good. Similar but more to the NW, less inland penetration, but still good enough.

Japan Lake effect 1.jpg

3. When we get low pressure, there's a good place for it to be, that generates moderate lake effect (not very strong because the air doesn't circulate from Siberia). But can generate #2 when it moves off to the NE.
4. Too far to the NNE. The air is not super cold because it's not traveling over land. Although it SEEMS good, it will NOT generate much lake effect.



5. Too far from the west. Lake effect happens, but the winds rake the coast and don't penetrate far inland. This was a big problem in 2015/16 season. Works better for resorts close to the coast in central Japan, and northern Honshu.
6. Winds are too slow and variable to generate much lake effect cloud. You can usually tell on the maps, where the isobars curve a lot.
Japan Lake effect 2.jpg


7. Too much loop off low pressure. This generates a northerly, but the air is not very cold, because it loops from the east
8 Low pressure in the middle of the Sea of Japan brings warm air from the south.
 
Last edited:

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
@Sandy - Can we get this thread stickied and possibly update the links to the images?
@Sandy seems as if your charts have disappeared from the first page. Is there any chance of resurrecting them?
Just try to educate myself to Kindergarten level ;)
Please be patient..... Photobucket has suddenly & quietly changed their terms of usage regarding 3rd party photo hosting from $0 per year to $399!!! Before I change to another 3rd party photo hosting site, they may relent, because of a heap of user backlash.
 
  • Like
Reactions: notty

Christophe09

First Runs
Aug 25, 2017
1
0
1
I look at the Japan posts regularly , but for the life of me I can't work out a lot of it , there are so many lines and numbers floating around I get lost in it all . I tend to look at this one a lot and look for the speckled clouds coming from NW http://www.jma.go.jp/en/gms/smallc.html?area=0&element=0&time=201311252300
[url=http://www.rachat-de-credit-simulation.com/simulation] Simulation de rachat de crédit
[/URL]
Could someone maybe do a tutorial thing with lines and notations drawn (a la VSG's drawings ) ?
I'm sure there would be others that would appreciate it also .
Ok thank you for the link
 

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
Bad systems.
1. A low pressure tough right in the middle of the Sea of Japan.

This type of double headed low, is generally the worst scenario for Hokkaido.

i.e.
Warm air is dragged into central Japan, but not from as far south, whereas it's long warm stream for Hokkaido.
2017-12-24-12z MSLP Japan.png


As the northern low approaches Hokkaido, cloud and warm air combine. OTOH, the cold air arrives in central Honshu earlier, while Hokkaido is still getting rain. A double headed low extends the northerly fetch more than with a single low, so it comes more from the north than the west, kicking in the lake/sea effect earlier for central Honshu.
2017-12-24-18z MSLP Japan.png



Hokkaido continues to get the injection of warm air on the eastern flank of the two lows.
2017-12-24-21z MSLP Japan.png
 
  • Like
Reactions: Froff Life

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
There were some questions about "Siberian Highs". @Tonester

These are the average pressures for January. You can see how the prevailing wind across Japan is a northerly, with the high rotating clockwise.
January+Average+Surface+Pressure+Systems+and+Associated+Circulation.jpg

Summer Winter.jpeg
 
  • Like
Reactions: Froff Life

Ramenman

A Local
Mar 3, 2014
5,222
6,562
563
2C and very cloudy + north-facing

-10C and very sunny + south-facing

which deteriorates snow condition on ski slopes more?
 

m2711c

One of Us
any chance of getting one of the wind direction vs snow total maps for the Tohoku region? I'm trying to understand how the winds affects the snow totals for Geto Kogen, Ani, and the areas around Shizukuishi. How much is the variation in the snowfall from resort to resort in this area from the same storm?

Thanks for the help.
 

Sandy

Dark Sith Lord of the Pool Room
Moderator
Ski Pass
Jan 1, 1998
70,359
28,813
1,515
Yokohama, Japan, Melb. Expat.
any chance of getting one of the wind direction vs snow total maps for the Tohoku region? I'm trying to understand how the winds affects the snow totals for Geto Kogen, Ani, and the areas around Shizukuishi. How much is the variation in the snowfall from resort to resort in this area from the same storm?

Thanks for the help.
This would take me a while to do, as I'd need to create a terrain map.....
However, Geto Kogen faces east, backing up to mountains about 70km from the coast.
Between the coast and Geto are coastal hills up to about 500m, a valley, and another row of higher hills up to 700m, a narrow valley, before rising to the mountains west of Geto up to just over 1000m. More of the snow falls on the western side, but much of it falls on the Geto side.
The two sets of hills "pre-rise" the air, cooling it. Since Geto is 70km from the coast, it needs a stronger breeze.
Best directions are west to northwest. It means that Geto does well earlier in the season when the winds are more westerly.
 

m2711c

One of Us
Thank you for the information. I am planning a trip in the last week of January - first week of February, and I am trying to get a better understanding of how the weather patterns affect the different ski regions. I'm hoping to pare down my list of ski areas to 7, but it's hard to do with each region having so many enticing options.
 
Remove ads with a
Ski Pass

Log in

or Log in using
Learn how membership works on these forums
Remove ads with a
Ski Pass