Heavy snowfall in Japan on the Sea of Japan side and elsewherein late 2021 and early 2022
1 February 2022
Tokyo Climate Center, Japan Meteorological Agency
https://ds.data.jma.go.jp/tcc/tcc

SummaryFrom late December 2021 to early January 2022, a series of heavy snowfall events hit
Japan on the Sea of Japan side and elsewhere, bringing unprecedented snowfall for thisperiod in the Kinki region and other areas. For example, a 48-hour snowfall record of78 cm was set at Hikone in Shiga Prefecture.
These conditions are partly attributed to continuous cold air inflow over the country
due to southward meandering of the polar front jet stream around Japan in association
with a blocking high over western Siberia.

1. Climate
From late December 2021 onward, cold air from Siberia flowed into the vicinity of Japanin association with an intensified East Asian winter monsoon. This caused heavy snowfall on
the Sea of Japan side from northern to western parts of the country and elsewhere (Figures
1-1, 1-2, 1-3, 1-4, 1-5, 1-6 and A1). New 48-hour snowfall records were set at five observation
stations (Table 1-1).
Snowfall on the Sea of Japan side of the Kinki region in December was 504% of the normal,
which was the second-highest for December after 2005 (640% of the normal) (Figure A1).
The average temperature during the period was also lower than normal nationwide.
2. Contributory factors
The primary factors contributing to these climate conditions are illustrated in Figure 2-1.
The heavy snowfall and low temperatures observed are partly attributed to southward
meandering of the polar front jet stream (PFJ) around Japan, which resulted in continuous
cold air flow over the region. The polar vortex in the troposphere, which is usually locatedover the Arctic region, was disrupted in association with this meandering and split into threeparts. One split vortex moved southward to the north of Japan and brought masses ofintensely cold polar air to the area. Cold air inflow from the Asian continent to the vicinity ofwestern Japan around 26 December 2021 was particularly strong for December (Figure 2-2).
The southward meandering of the PFJ around Japan was likely influenced by a blocking

high over western Siberia and Rossby wave packet propagation from Europe. The subtropicaljet stream during this period also meandered northward over the west of Japan andsouthward over eastern parts, creating favorable atmospheric circulation conditions forsouthward inflow of cold air over the country. Such meandering over Asia may be attributable
to anomalous convective activity, which was suppressed over the Indian Ocean and enhanced
over and around the Philippines in association with the prevailing La Niña event.
This analysis was performed in collaboration with the TCC Advisory Panel on Extreme Climatic
Events (a JMA body staffed by prominent climatologists from the fields of academia andresearch).

Figure 1-1. Average cumulative snowfall [cm] in regions designated under the Act on Special
Countermeasures for Heavy Snowfall Areas (1 November 2021 – 20 January 2022)

Figure 1-2. Maximum 48-hour snowfall [cm] for 25 December 2021 – 4 January 2022

Figure 1-3. Maximum snow depths [cm] for 25 December 2021 – 4 January 2022

Figure 1-4. Ratio of maximum snow depth for 25 December 2021 – 4 January 2022 to theclimatological normal of annual maximum snow depth [%]The base period for the normal is 1991 – 2020.

Figure 1-5. Time-series representations of 5-day running mean temperature anomalies [°C]for November 2021 – January 2022
The base period for the normal is 1991 – 2020.

Figure 1-6. Distribution of mean temperature anomalies [°C] for 25 December 2021 – 4January 2022
The base period for the normal is 1991 – 2020.

Figure 2-1. Characteristics of atmospheric circulation bringing heavy snowfall and low
temperatures to Japan from late December 2021 to early January 2022

Figure 2-2. Time-series representation of 850 hPa temperature (approx. 1,500 m) over Japan(30 – 45°N, 125 – 145°E) from December 2021 onward
The temperature on 26th December was the ninth lowest for December since 1958.

Table 1.1 Record-high snowfall locations1 25 December 2021 – 4 January 2022

3-hour snowfall records
Prefecture
Location

Observation (cm)

Previous
record Startof Description(cm) (year)
observation
21 (1996)
1979
Joint recordhigh

AomoriGoshogawara(五所川原)

21

Shiga

Maibara (米原)1616 (2018)

Observation (cm)36

Previous
record Startof Description(cm) (year)
observation
30 (2011)1999

4342 (2017)

Observation (cm)

6-hour snowfall records
Prefecture
Location
Hokkaido

Iwamizawa(岩2001

Joint recordhigh見沢)
Tottori

Chizu (智頭)12-hour snowfall records
Prefecture
Location

1981

Niigata

Tsugawa (津川)54

Previous
record Startof Description(cm) (year)
observation
53 (2003)
1980

Shiga

Hikone (彦根)3736 (2017)

2001

Hyogo

Wadayama (和 4343 (2020)

1981

田山)
24-hour snowfall records
Prefecture
Location

Observation (cm)Shiga

Hikone (彦根)

68

Hyogo

Wadayama (和 71

Previous
record Startof Description(cm) (year)
observation
44 (2012)
2001
64 (2000)

田山)

1

Joint recordhighhttps://www.data.jma.go.jp/obd/stats/data/mdrr/periodstat/index.htmll

1981

Table 1.1 Record-high snowfall locations 25 December 2021 – 4 January 2022 (Continued)

48-hour snowfall records
Prefecture
Location

Observation (cm)

Hokkaido

Koetoi (声問)AomoriNoheji (野辺地) 66

54 (2010)

2008

Shiga

Maibara (米原)74

63 (2012)

2001

Shiga

Hikone (彦根)78

65 (2017)

2001

Kyoto

Maizuru (舞鶴)71

62 (2012)

2001

Observation (cm)

Previous
record Startof Description(cm) (year)
observation
78 (2013)
2006

72-hour snowfall records
PrefectureLocation

76

Previous
record Startof Description(cm) (year)
observation
67 (2013)
2006

Hokkaido

Koetoi (声問)92

AomoriNoheji (野辺地) 85

57 (2021)

2008

Shiga

Hikone (彦根)79

66 (2017)

2001

Kyoto

Maizuru (舞鶴)71

67 (2005)

2001

Figure A1. Climatologicalregions of Japan
JMA’s seven regional divisions
for climate monitoring andforecasting (the Sea of Japanand Pacific sides of northern,eastern and western Japan, andOkinawa/Amami)