The unparalleled solo hiker, Buntarō Katō, lost his life to a heavy snowstorm. The cause was the JPCZ, which continues to bring heavy snow in recent years.

Happy New Year, everyone. After a scorching summer and a warm autumn, heavy snow began to fall primarily along the Sea of Japan coast in late December, finally bringing a winter-like season.

According to the three-month forecast, January will have lower-than-average temperatures, with more snow than usual along the Sea of Japan coast, and several cold waves are expected after the New Year. February is forecasted to have average temperatures, while March is expected to be warmer than average nationwide, suggesting that while this winter may be harsh, spring will likely arrive early.

Well, this time I would like to take up the Kitakama Ridge about 90 years ago. The so-called "Omote Ginza" course, which traverses from Mt. Tsubame toMt. Yarigatakein the Northern Alps, is a popular course for many people, but from here you can witness the majesty of theMt. Yarigatakeand the Kitakama Ridge that runs along it.

For me, the Northern Karamatsu Ridge, which left a lasting impression when I traversed the Omote Ginza route with a three-person high school party 45 years ago ( photo1 ), is something I still cannot forget.

After becoming a working adult, I was finally able to climb the Northern Karamatsu Ridge from the right branch of the Northern Karamatsu Valley in autumn, but even in the snow-free season, it was a nerve-wracking route. During the snow season, the Northern Karamatsu Ridge is said to be a route reserved only for highly skilled and physically fit experts.

There are two legendary hikers who lost their lives during the harsh winter season on the Northern Karamatsu Ridge. One is " Bivouac in the wind and snow Akira Matsutō from "", and the other is from Jirō Nitta's novel " A solitary person " This is Kato Fumitarou from "

Approximately 90 years ago, Buntarō Katō lost his life on the Northern Karamatsu Ridge. We have vividly reconstructed the weather conditions at the time of his accident, and in this article, we will present the results and discuss the lessons that remain relevant today.

The circumstances of Buntarō Katō's accident and the historical context of the time.

Kato Buntaro was born on March 11, 1905 in Shinonsen Town, Hyogo Prefecture. He was an active mountaineer from the Taisho to Showa eras, leaving many mountaineering records behind, including a solo ascent of Mt. Yarigatake in winter. Many of Kato Buntaro's mountaineering expeditions were solo, but not all of them were solo.

Buntarō Katō had been a long-time partner of Tomihisa Yoshida, an expert in rock climbing, and they climbed the Northern Ridge of Mae-Hotaka together. In Jirō Nitta's novel "The Lone Climber," it is written as though their trip to the Northern Karamatsu Ridge caused the accident, but this does not seem to be the case.

On January 3, 1936, Buntaro Kato and Tomihisa Yoshida attempted the Kitakama Ridge from their shoulder hut (nowMt. YarigatakeSanso), but disappeared in a blizzard there. Bad weather and heavy snowfall made the search extremely difficult, and the bodies of the two men were not found until four months later, on April 17.

Buntarō Katō was found about 500 meters up from the Senden Junction on the Tenjōzawa side, while Tomihisa Yoshida was found 200 meters further up. The fact that their discovery sites were not far apart and that an ice axe was placed as a marker at Yoshida's burial site indicates that the two shared a strong bond until the very end (a topographic map of the Northern Karamatsu Ridge area is Figure 1 reference).

The year 1936, when this accident occurred, was before the start of World War II, but it was a tense pre-war period, marked by events such as the February 26 uprising, where young officers attacked former Prime Minister Korekiyo Takahashi.

On the other hand, there were also uplifting events, such as Hideko Maehata becoming the first Japanese woman to win a gold medal in the 200m breaststroke at the Berlin Olympics, and legendary pitcher Eiji Sawamura achieving the first no-hitter in Japanese professional baseball history. In the mountaineering world, Rikkyo University's Alpine Club succeeded in the first Japanese Himalayan expedition, reaching the summit of Nanda Kot (6,861m) in India.

Reconstructing the weather conditions of the time using NOAA's reanalysis data.

In 1936, there were no weather satellites or supercomputers for weather forecasting. Instead, staff at the Central Meteorological Observatory, the predecessor of the Japan Meteorological Agency, manually drew weather maps to provide daily forecasts.

The weather map created by the Central Meteorological Observatory at 6 a.m. on January 5, the third day after Buntarō Katō went missing, Figure 2 is shown here. It depicts a winter pressure pattern with high pressure in the west and low pressure in the east, causing snow from the Tohoku region along the Sea of Japan coast to Hokuriku and San'in. However, this map does not reveal how severe the conditions were near the Northern Karamatsu Ridge.

So, 20th Century Reanalysis Data by NOAA (National Oceanic and Atmospheric Administration). Using this, I attempted to recreate detailed weather charts from that time. NOAA's 20th Century Reanalysis Data includes information that reconstructs atmospheric conditions using modern supercomputers based on actual observation records from that era. By itself, it is merely numerical data, but by extracting and analyzing the necessary data, it becomes a weather chart brought to life.

It should be noted that the 20th Century Reanalysis Data actually spans from 1836 to the 21st century. One of the major analysis cases that garnered significant attention is " 1902Mt. HakkodaColumn on the March in the Snow "is.

When recreating the surface weather chart for Bunjiro Kato's mountaineering accident this time, a surprising fact was revealed. The weather chart for 9:00 AM on January 5 is Figure 3 shown here. The color coding represents hourly precipitation (adjusted using observation records from the Takada Weather Station), solid lines indicate isobars, and arrows represent surface winds. Converting the precipitation unit from millimeters to centimeters gives an approximate hourly snowfall amount.

On the surface weather chart, a convergence line (dashed line) known as the JPCZ (Japan Sea Polar Air Mass Convergence Zone) is clearly visible over the Sea of Japan. The JPCZ often brings heavy snow disasters to regions along the Sea of Japan, and it also appeared during the heavy snowfalls around December 23 and 27 last year (2024). This JPCZ and the associated precipitation area are moving from the Sea of Japan toward the Hokuriku region. I never imagined that the reanalysis data could so vividly recreate the JPCZ from 90 years ago.

In the first place, JPCZ is caused by the convergence (collision) of the northwest monsoon that bypasses the north and south sides of the longMt. Hakuvein (the highest peak is Mt. Paektu (2744m) near the border between North Korea and China, and converges (collides) in the Japan Sea. The colliding air cannot go down because of the Sea of Japan, and snow clouds form one after another as they rise while receiving water vapor from the warm Sea of Japan. This is the mechanism by which JPCZ causes heavy snowfall. According to observations by ships, a large amount of water vapor can be seen rising from the Sea of Japan, where the water temperature is more than 10°C even in the middle of winter, when the temperature is below freezing.

Figure 4 The weather chart for 700 hPa (approximately 2,900 meters altitude) at the same time is shown here. The color coding and dotted lines represent 700 hPa temperatures, solid lines indicate 700 hPa geopotential height lines (equivalent to isobars on surface weather charts), and barbs represent 700 hPa winds. Near the Kita-Kamaone Ridge, the conditions were extremely harsh, with a temperature of −21°C and westerly winds at 20 m/s.

Mt. FujiAccording to the weather station's record, it was -19°C, so I think the temperature reproduced is correct. We were able to verify that the area around the Kitakama Ridge was in a state where visibility was completely poor due to the blizzard as reported.

In addition to the JPCZ, a 'three-wave pattern' pressure system similar to the 1938 heavy snowstorm.

And as for how heavy the snowfall was, it is more accurate to look at the actual observation records by the Takada Weather Station in Niigata Prefecture than the reanalysis data. The Takada Weather Station was established in 1921 (Taisho 10) and was abolished in 2007 (Heisei 19) (now it is an unmanned automatic observatory), but there are valuable observation records from the time when it was manned observation.

Figure 5 This shows the handwritten observation records of snowfall and snow depth from Takada Weather Station in January 1936. The unit '糎' is a kanji read as 'centimeter,' which reflects the passage of time.

The maximum snow depth on January 2, the day before Buntaro Kato went missing, was 45 cm, but by January 6, it had reached approximately 140 cm, with 1 meter of fresh snow accumulating. These handwritten observation records from Takada Weather Station were analyzed and graphed. Figure 6 The vertical bars represent snowfall, and the solid line represents the maximum snow depth.

After Buntaro Kato went missing on January 3, a large amount of snow accumulated by January 6, and the winter pressure pattern strengthened again after January 14, leading to increased snow depth by January 22. Due to this heavy snowfall, Kato and his companions' bodies were deeply buried in the snow and were not discovered until April 17 of the same year.

So, why did such heavy snowfall occur? This season (2024-2025) is experiencing a cold winter for the first time in a while, likely influenced by the La Niña phenomenon, which lowers sea surface temperatures in the equatorial eastern Pacific. Conversely, the El Niño phenomenon often leads to mild winters. However, 1936 was a year when neither La Niña nor El Niño occurred. So, what caused the heavy snowfall?

The answer lies in the atmospheric pressure pattern centered around the Arctic. Figure 7 This shows the 500 hPa weather map of the Northern Hemisphere at the same time, recreated using NOAA's reanalysis data. The color coding represents 500 hPa temperatures, and the solid lines represent 500 hPa geopotential height contours. You can see cold air from the Arctic being released in three directions: Europe, North America, and Asia. This is known as the 'three-wave pattern' pressure configuration.

Although not included in the column article, in fact, January 1963 (Showa 38)Mt. YakushiDistress accident at that time, the 'three-wave pattern' pressure configuration was also present. 1963 was the year of the Sanpachi Heavy Snowfall. The winter of 1962/1963 also did not experience the La Niña phenomenon. These are good examples showing that cold waves and heavy snowfall are not solely caused by the La Niña phenomenon.

Even with climate change, the risk of heavy snow caused by the JPCZ remains.

So, what will happen to the snow in the mountainous regions on the Sea of Japan side in the future amidst climate change? To find out, I examined and graphed the trends in maximum snow depth in Maizuru (Kyoto Prefecture). Maizuru was chosen because it has observation records of maximum snow depth dating back to 1948, its terrain forms a bay shape that is less affected by the warm Tsushima Current, and it is more prone to snow compared to other Japan Meteorological Agency observation points near the central mountains on the Sea of Japan side. Therefore, it is considered to closely reflect the trends in maximum snow depth in the mountainous regions on the Sea of Japan side.

Figure 8 The results are shown here. It can be observed that heavy snowfall occurs roughly once every 5 to 10 years. Among these, maximum snow depths exceeding 70 cm occurred four times in the latter half of the observation period. At least the two most recent instances in 2012 and 2022 were confirmed to be heavy snowfalls caused by the JPCZ (Japan Sea Polar-air Convergence Zone) through weather satellite images and surface weather maps. Similarly, analyses of surface weather maps using the Japan Meteorological Agency's JRA-55 reanalysis data suggest that the heavy snowfalls in 1984 and 2000 were also likely caused by the JPCZ.

Figure 8 From this, it can be seen that the average maximum snow depth is decreasing at a rate of 3 cm per 100 years. However, it warns that the risk of heavy snowfall caused by the JPCZ will remain in the mountainous regions on the Sea of Japan side in the future. An example of this is the February 2004 Daichozan mountain accident where heavy snowfall caused by the JPCZ led to the incident. The greatest lesson from this investigation is that we must never underestimate the risk of heavy snowfall in mountainous regions in the future.