Sorry for a long wait for another update, here’s the next edition of the Japanese long range snow forecast.
9th-10th of January
EPS Control shows us a system on the 9th-10th of January, spear-headed by a low over Hokkaido, bringing heavy snowfall there.
It also features moderate-heavy snowfall for Honshu, but temperatures aren’t as great particularly the further south you get.
12th-13th of January
A low sweeps to the south, bringing heavy snow to higher elevations of Central Honshu and heavy rain to the lower elevations over the 12th, easing over the 13th on the EC Monthly model.
14th-19th of January
On the 14th and 15th, weak winds and westerlies bring light-moderate snowfall to Central Honshu. On the 16th, NW winds come in to bring moderate-heavy snowfall for Honshu and parts of Hokkaido, and then easing on the 17th. On the 18th and 19th, another bout of NW winds brings more snowfall for Central Honshu on EC Monthly.
21st-24th of January
On the 21st and 22nd of Jan, EC Monthly forecasts moderate-heavy snowfall for Honshu. This eases over the 23rd and the morning of the 24th.
25th-28th of January
A very strong and cold system brings heavy snowfall on the 25th of Jan to Honshu and parts of Hokkaido. This systems continues through to the 27th and 28th.
East Asian Mountain Torque
We are currently in a negative EAMT, and this is part of the reason why rain is associated with the systems arriving in the short term. It means that there is troughing in China, which allows rain-bearing lows to develop to the south of Japan.
I expect a positive EAMT to develop in the next few days to counter the current negative trend for a brief moment. This helps to develop ridging in Eastern China, which improves our chances for snowfall in the first 10 days of January.
However from about the 1st to 3rd of Jan, we will see another -EAMT come into play, and this one could be sustained for a while. This would increase chances of rainfall and decrease cold in the middle two weeks of January from Japan.
As you can see in the model guidance, the troughing over Siberia early in January weakens the Siberian High, which weakens our chances for cold and snowfall in Japan as well.
The AO is looking positive in the medium term, and throughout January, which decreases the chance of strong snowfall for Japan.
The stratosphere is likely to remain stable in the early stages of January, because of a lack of tropospheric setup to help a weakening of the Stratospheric Polar Vortex. There still are decent background conditions for a potential SSW later in January or February. A SSW would improve conditions for the Japanese later season.
A Phase 7 MJO is good for Japanese snowfall. The forecast that we briefly pass through it on RMM indexes helps to explain the forecast for a good period of snowfall in early January.
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.
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