Well the not so great Japanese snowfall season continues, and with that comes more analysis looking into the later parts of the snowfall season.
The 26th of January, or Australia Day is forecasted by EC Monthly to feature heavy rainfall for Central Honshu, with some snowfall for Northern Honshu. The low moves across over the 27th.
As the low slowly moves across Honshu on the 27th, we start to see a gearing up for a period of big snowfall created by another low, this time in the Sea of Japan, for the 28th, 29th and 30th of January for Honshu and Northern Hokkaido. We really start to see cold air come down with this one, as forecasted by EC. The snowfall should ease over the 31st.
EC Monthly shows a strong lake/sea effect snowfall event moving over Honshu and much of Hokkaido starting over the early hours of the 1st of Feb, and not easing until the morning of 5th of Feb.
This marginal low pressure system would deliver per EC, rainfall to lower altitudes and snowfall to higher altitudes and further north on Honshu over the 7th of Feb, easing in the early hours of the 8th.
Well my seasonal prediction (for a good early season) has gone pretty bad this year. Largely because of the base state that has been over the Indian and Pacific Ocean basins. In order to bring Japanese snowfall, we want consistent positive East Asian Mountain Torques, which bring strong Siberian Highs that drive snowfall into Honshu and Hokkaido.
This year we have had a weaker than normal Siberian High, and a weaker than normal Aleutian Low. This is part of why not much activity has occurred in the stratosphere, but also why lows haven’t been passing from the north, and the cold air in Siberia is less organised and less able to move down into Japan.
GFS forecasts this weaker activity to persist in the short term and improve in the longer term. This may help our prospects for snowfall in the last 10 days of January and into February.
Instead of a strong Siberian High and mechanism to bring lake/sea effect snowfall conditions, we have seen low pressure consistently present in East Asia, bringing lows down along the Pacific coast of Japan and bringing rainfall to Honshu.
+EAMTs in the past few weeks are currently helping snowfall conditions a bit, bringing more favourable surface conditions, but the medium term is likely to bring more unfavourable East Asian troughing with current and forecasted -EAMT.
A MJO pass through Phase 7 in the Pacific is likely to help improve conditions for late January and early February for Japanese snowfall. Based on this “timetable”, mid February will be the lull and late February will see an improvement into March.
Overall the weird nature of this season and the current climatic conditions has reduced my certainty of the state of things. But I certainly see potential for some improvement for the later stages of the Japanese snowfall season with some decent snowfall events on the horizon, given the (slowly) improving Indian Ocean base state. But it shouldn’t be taken as a given, the guidance shows little in the way of positive tropical activity for February. It would lack the amplitude needed to get past the East Asian troughing and the poor state of the Siberian High at this time.
The stratosphere and the Arctic state are hardly satisfying for those who want a repair to the Siberian Ridging problem. A +AO tends to be poor for Japanese snowfall. My confidence on a late season SSW is weakening, but still very much a possibility.
In summary, I believe the last ten days of January and the first week of February should be more desirable in terms of snowfall prospects. But caution should be taken with a lurking -EAMT in the region. I’m somewhat optimistic, but the potential for turbulent times is still there. Probably not so great for much of the remainder of February IMO. It all depends on the progression of the current climatic base state, and the conditions closer to the Arctic and in Siberia.
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Disclaimer: There is low skill asssociated with using long range model forecasts to find snow systems.
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