Japanese Long Range Outlook 23rd November

Hello and welcome to my first long range outlook for the Japanese winter. This update, we will lay the foundations, and look out towards Christmas, which is in just over a month.


7-9 Dec

EPS Control(not pictured) shows moderate snowfall for Hokkaido on the morning of the 7th for about 12 hours or so. GFS shows moderate-heavy snowfall for Hokkaido on the 9th.

10-12 Dec

EC Monthly shows a rainfall event for Central Honshu by and large, bringing heavy rainfall, starting slowly on the 10th, and strengthening over the 11th and 12th unfortunately. Heavy snowfall does occur in Hokkaido however on the 11th and 12th. CFS shows moderate snowfall for Central & Northern Honshu as well as Hokkaido from the 10th – 12th, with more NW winds for Central Honshu being present over the 10th.

13 Dec

There is potential, according to EC Monthly, for some snowfall after the rain in Central Honshu, but a NE wind hampers the possibility of a snowfall on the ranges. Moderate snowfall continues in Hokkaido easing later on the 13th, and into the 14th. CFS shows light snowfall over Hokkaido over the 13th and 14th, and a potential rainfall event from the south on the 15th for Central Honshu.

18-19 Dec

A nice NW wind pushed trough on EC Monthly hits Hokkaido and Honshu, bringing moderate-heavy snowfall over the afternoon of the 18th. The winds become more awkward, and it shifts to just Central Honshu on the 19th, easing out to sea in the afternoon. CFS shows a NW wind event bringing snowfall to Honshu and Hokkaido on the 17th, thru to the 19th.

21-23 Dec

A Low deepens in the Sea of Japan over the 21st on EC Monthly, and crosses Honshu. The temperatures are cold enough for snowfall most of the way, and expect this scenario to deliver it in heavy amounts over the 21st, and then more snowfall generated by a good NW wind over the 22nd and easing over the 23rd. Hokkaido gets moderate-heavy snowfall over the 21st and 22nd, light snowfall over the 23rd. CFS shows a NW wind event for heavy snowfall for Honshu on the 20th, and another for Honshu and Hokkaido on the 22nd and 23rd.

Climate Drivers

The MJO is currently at roughly Phase 5. Phase 7 MJO is expected in the next 10 day period, which is favourable with a few days lag towards Japanese snowfall, because of an influence on the East Asian Winter Monsoon.

The Arctic Oscillation is currently negative, and is expected to stay so until about Dec 8th. The negative phase is better for Japanese snowfall. It goes positive until January, so a particularly unfavourable period ahead. The CFS expects a -AO however for December, January into mid February, which is a positive development for Japanese snowfall.

The SPV (Stratopsheric Polar Vortex) is forecast to weaken in the next 10 days by GEFS, because of a wave 1 disturbance. CFS expects it to stay weak throughout the winter, with little options for a proper big SSW event to really change the scales. But there is room for more minor disturbances that can make the AO more negative. EPS Weeklies forecast for a strong Aleutian Low over the next month, and favourable seasonal conditions (ENSO) assist with more SSWs and a weaker SPV. The AAM is forecast to be negative for Early-Mid December, which doesn’t favour a strong Aleutian Low or SSW events.

The climate drivers don’t look very great, beyond Early December. The models do show some hope of a few snowfall events breaking through later in the month, so hopefully those ideas continue.

Thanks so much for reading. I hoped you enjoyed reading it.

Disclaimer: There is low skill asssociated with using long range model forecasts to find snow systems. All systems you see here will change, as the date gets closer and may not eventuate all together. I find the chase of these long range snow systems awesome, so come and join me! The climate driver forecasts tend to have quite a bit more skill than the model forecasts, but certainly don’t put all your money on them. However, climate drivers are an awesome tool to explain the weather around us.

Thanks again for reading this Japanese long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

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