Winter-like atmospheric pressure patterns strengthened in early December, causing barges to appear in the seas around Japan [Marine Summary 2025/11/30-12/6]

2025/12/11 14:06

This is a summary of the ocean from 2025/11/30 to 12/6.



#Pressure distribution and waves
On the 30th, a low pressure system accompanied by a front passed near Hokkaido.
Wave height of 2 to 3 m in the northern and central parts of the Sea of Japan.
On the 1st, another low pressure system developed and passed near Hokkaido.
Wave height was 3m in the Japanese waters in the morning, and 5m in the Sea of Okhotsk at night.

On the 2nd, a low pressure system in the Sea of Japan was developing and moving northeast.
From the 3rd to the 4th, a winter-like pressure pattern strengthened near Japan.
On the 4th, wave heights widely exceeded 4 meters in the Japanese waters and the Pacific Ocean.

On the 5th, an anticyclone emerged from the west, and the high waves gradually subsided from the west.
On the 6th, the area around Honshu was covered by a belt-shaped high pressure system.
In the morning, high waves continued off the coast of Sanriku on the edge of the high pressure system and from west of Hokkaido to off the coast of Akita, but subsided by night.



#Sea surface temperature
Sea surface temperatures in the Japanese waters continue to be lower than normal along the coast of Hokkaido.
In the central and western regions, sea levels continued to be higher than normal or significantly higher.

In the East China Sea, the sea area is expanding at normal levels.
South of Japan, sea areas continue to be at normal levels.
The Izu Islands have returned to normal levels, but waters off the coast of the Tokai region continue to be below normal levels.

In the eastern part of Japan, temperatures were significantly higher than normal, with temperatures up to 4 C higher.
The waters off the coast of Sanriku continue to be at normal levels. The sea off the southeast coast of Hokkaido was lower than normal, and the Sea of Okhotsk remained at normal levels.

Tomorrow (Friday) intense cold; heavy snow and blizzard on the Japan Sea side; widespread stormy weather from the weekend to the beginning of the week, affecting transportation [Weekly weather]

2025/12/11 12:38

Weekly weather points
#The coldest air of the season will arrive tomorrow
#Friday the 12th (Friday) to 13th (Saturday) will be the coldest of winter
#From the 14th (Sunday) to the 15th (Monday) there will be stormy weather and severe storms in northern and eastern Japan



Tonight, a low pressure system near Hokkaido is expected to develop and move towards the waters near the Chishima Islands.
Tomorrow, the 12th (Friday), a winter-like pressure pattern will strengthen, and cold air similar to midwinter will flow into the
sky.

Looking at the forecast for the cold air in the air at noon tomorrow,
more than the cold air expected to bring heavy snow,
an even stronger cold air of minus 42 degrees Celsius is expected to flow over Hokkaido.

The lowest temperature so far this season was -39.4c, which was observed at around 5000m above Sapporo on December 4th (Thursday), and the cold air that will arrive tomorrow is likely to be the strongest this season.

Due to the effects of this strong cold air, there will be widespread snow on the Sea of Japan side,
There will likely be heavy snowfall in some places, especially in Tohoku and Hokkaido.
Also, there will be heavy snow along the mountains on the Sea of Japan side, and there is a possibility that
heavy snow warnings will be announced in Hokkaido, Aomori prefectures, northern Nagano prefectures, etc. until
12th (Friday).



In addition, the temperature will not rise due to the cold air,
tomorrow, the 12th (Friday), the maximum temperature in Tokyo, Osaka, and Nagoya will be 10c,
It will be bitterly cold even on the Pacific side.

Furthermore, on Saturday the 13th, the maximum temperature in Tokyo will be 8c, which is likely to be the coldest of the season.

Wear warm winter clothing such as down coats, gloves, and scarves when you go out.



Due to the developing low pressure system from the 13th (Sat) to the 14th (Sun),
the weather will be rough with rain, snow, and strong winds across the country.

Especially on the 14th (Sunday), there is a risk of warning-level storms, heavy rain,
heavy snow in eastern and northern Japan, and the weather is likely to be very stormy in northern Japan.

Please be aware that transportation such as aircraft, Shinkansen trains, and expressways may be affected.




#Stormy weather continues into the 15th (Monday) of the week#

Even into the 15th (Monday), there will be strong snow and wind in northern Japan, with
warning-level storms and heavy snow in some places.

Also, the cold air will remain until the middle of next week, so the December-like cold will continue even on the sunny Pacific side.

The air on the Pacific side is dry, so
Please be careful about your physical condition, especially if you catch a cold.

Weather for the week: Heavy snow and stormy weather on the Sea of ??Japan side on the weekend; cold rain also on the Pacific side of western and eastern Japan

2025/12/11 09:03

The weather will be severe over a wide area this weekend and into the beginning of next week. Snow will become heavier on the Japan Sea side, and there is a risk that snowfall will increase rapidly, especially in Hokkaido and Tohoku.



Tomorrow, the 12th (Friday), extremely cold air with temperatures below -12c at an altitude of approximately 1500 meters is expected to move southward to the Hokuriku region near Honshu.
Deep snow clouds will flow into the Hokuriku region from the Sea of Japan side of northern Japan, and even flat areas will become snowy. Locally, the snow may become heavier in a short period of time, leading to a sudden increase in snowfall. In addition, northerly winds will become stronger, causing snowstorms in some places, especially along the coast. Please be careful of poor visibility due to blizzard and traffic obstruction due to snow.




From Saturday the 13th to Sunday the 14th, two low pressure systems will pass over the Sea of Japan and the southern coast of Honshu, respectively, and the weather will deteriorate from the west. The two low pressure systems will merge into one from the 14th to the 15th, and the area around Honshu will have a winter-like pressure pattern of high in the west and low in the east.
For this reason, from the 13th to the 14th, there will be widespread rain and snow from northern Japan to eastern Japan and western Japan on the Sea of Japan side, and there will also be widespread cold rain on the Pacific side of eastern and western Japan. It looks like the wind will be strong and the weather will be rough.
The weather is expected to improve on the Pacific side from the 15th (Monday) onwards, but from the Sea of Japan side of northern Japan to the Hokuriku region, rain and snow days are expected to continue due to the effects of cold air and low pressure in the upper atmosphere.

As the cold air moves south, the temperature will change significantly. Tomorrow, the 12th (Friday), temperatures will be below 5c in many places from the Sea of Japan side of northern Japan to Hokuriku, and the predicted maximum temperature in Sapporo is -4c. Temperatures are expected to reach 9c in Tokyo on Saturday the 13th, and there will be places on the Pacific side where the temperature will not reach 10c during the day, a midwinter cold. It is expected that the weather will continue to be cold, especially in the mornings and evenings, and the winter-like cold will continue after the end of the week. Please take all possible measures to protect yourself from the cold and stay in good physical condition.

El Nino monitoring bulletin: La Nina-like conditions will rapidly resolve at the end of winter

2025/12/10 21:12

On the 10th (Wednesday), the Japan Meteorological Agency announced the latest El Nino monitoring bulletin.

Currently, the situation appears to be normal, with neither El Nino nor La Nina occurring, but conditions are close to La Nina. This situation is expected to continue until the beginning of winter, but is expected to quickly resolve after that.

The difference in sea surface temperature in the El Nino monitoring area in November from the standard value was -0.5c, which was lower than the standard value. Additionally, the five-month moving average used to determine the occurrence of El Nino and La Nina phenomena in September was -0.4 C, a value close to the standard value.
Sea surface temperatures in the equatorial Pacific Ocean remained higher than normal in the western region and lower than normal in the central and eastern regions. The easterly winds (trade winds) in the lower atmosphere of the equatorial Pacific region were stronger than normal throughout the region, and convective activity became inactive near the international date line in the equatorial Pacific region.

From the above, although it is a normal state where neither El Nino nor La Nina phenomena have occurred, the situation is close to that of La Nina.



According to the Japan Meteorological Agency's coupled atmosphere-ocean model, sea surface temperatures in the El Nino monitoring area are expected to remain lower than standard values at the beginning of winter due to continued strong trade winds in the equatorial Pacific.
However, after that, the atmosphere-ocean coupling is expected to weaken and the low sea surface temperature will rapidly disappear. Sea surface temperatures are expected to rise from late winter to spring and remain close to standard values.

From the above, the La Nina-like conditions are expected to rapidly resolve towards the end of winter, and normal conditions will continue into spring.


#What is the El Nino/La Nina phenomenon
The El Nino phenomenon is a phenomenon in which sea surface temperatures are higher than normal from the equatorial Pacific Ocean near the international date line to the coast of South America, and this condition continues for about a year.
On the other hand, a phenomenon in which sea surface temperatures continue to be lower than normal in the same area is called a La Nina phenomenon.

Once an El Nino or La Nina phenomenon occurs, it is thought that abnormal weather will occur all over the world, including Japan.

Tomorrow, the 11th (Thursday), there will be widespread rain due to low pressure and a front. Be careful of lightning and gusts of wind.

2025/12/10 20:16

Tomorrow, the 11th (Thursday), the center of the high pressure system is expected to leave the vicinity of Honshu, and the low pressure system and front are expected to pass near northern Japan. There will be a pressure trough on the Sea of Japan side, and another front will approach from the East China Sea. For this reason, the weather will be downhill from northern Japan to western Japan, mainly on the Sea of Japan side.





Hokkaido has been snowing since dawn, and it looks like it will continue to snow after that. The wind will be strong and there will be snowstorms in some places. At night, as strong cold air moves southward, there is a risk of heavy snowfall even in the plains.

In the Tohoku region, it will rain in the morning, but in some places it will gradually change to snow in the evening and night. Winds will be strong and the weather will be rough, especially on the Sea of Japan side, and there are likely to be some places where there will be heavy rain and snow accompanied by thunder. The ground may be loose in some places due to the effects of previous rains and earthquakes, so please be careful of landslides.
In the afternoon, as the front moves southward, atmospheric conditions will become unstable on the Japan Sea side from Hokuriku to northern Kyushu, and the rain is likely to spread. The wind is expected to gradually strengthen, so please be careful of sideways rain, strong winds, and high waves in coastal areas. Also, be careful of lightning, tornadoes, strong wind gusts, and hail.

It looks like it will be sunny in many places on the Pacific side from Kanto to Kyushu, but it is likely to rain in places in the afternoon. The air in the Kanto region is dry, so be careful when handling sources of fire.

During the day, the temperature in some places is likely to be higher than on the 10th (Wednesday) due to the influence of warm air from the south. However, after the front passes, cold air will move south, so there will be some places where it gets cold quickly at night. The temperature difference between day and night tends to be large, so please try not to get sick.

12th (Friday) Strong cold air moving south; 14th (Sunday) Stormy weather nationwide; Northern Japan frequently experiences warning-level storms and heavy snow [Weekly weather]

2025/12/10 11:53

Today, the 10th (Wednesday), will be covered by high pressure, resulting in mild winter skies mainly over western and eastern Japan.

The snow and rain in northern Japan and Hokuriku will stop by the afternoon, and the weather is expected to gradually improve.

However, the weather changes quickly, and by tomorrow (Thursday) the 11th, a low-pressure system with cold air will develop and approach northern Japan,
It is likely that there will be rain and snow in Hokkaido and northern Tohoku in the morning.



#The next day, on the 12th (Friday), strong cold air will move south#

On the 12th (Friday), a winter-like pressure pattern will temporarily strengthen, and strong cold air comparable to midwinter will flow into the sky over
.

In northern Japan and Hokuriku, there will be warning-level storms,
with snow, and it is likely to become a blizzard in some places.
Also, the snow is getting heavier, and there are likely to be heavy snowfall in Hokkaido and Aomori.

Temperatures are expected to drop in the Kanto region and other parts of the Pacific Ocean, and it will be midwinter cold.




#There is a risk of stormy weather nationwide on the 14th (Sunday)#

Furthermore, looking at the forecast weather map for Saturday and Sunday,
There will be two low pressure systems sandwiching Honshu on the 13th (Saturday),
The low pressure systems in the Sea of Japan and the southern coast of Honshu are both expected to develop and move northeast.

On the 14th (Sunday), the low pressure systems will coalesce into one over northern Japan and
will further develop.

Although the cold air will be stronger on the 12th (Friday),
the weather is likely to be rough with rain, snow, and strong winds across the country.



Looking at the rain, wind, and snow forecast for the 14th (Sunday), it will rain in western Japan and the Tokai region around 3:00 a.m. (picture on the left),
in many places in the Kanto-Koshin and Tohoku regions.

In the afternoon (picture on the right), snow and rain are expected to spread across northern Japan and Hokuriku, and
winds from the west and north are expected to become stronger nationwide.

Especially in northern Japan, it is likely that there will be warning-level storms, and
a blizzard with snow in some places.

There is a risk of heavy snowfall on the Pacific side of Hokkaido and the Sea of Okhotsk side.

In northern Japan, the weather often becomes stormy from the weekend until the beginning of the week.

Even in Aomori, which was damaged by the recent big earthquake,
heavy snow and strong winds are expected, so please stay inside a sturdy building.




Looking at the temperature in the weekly forecast,
13th (Saturday) will have a maximum temperature of 9c in Tokyo, which will be midwinter cold.
It's raining cold and it feels colder than the temperature.

It will continue to be cold, with snow and cold rain continuing on the Sea of Japan side until the end of the week.

On the Pacific side, it is expected to be sunny again in many places next week, and the air will be dry.

It's bitterly cold in northern Japan, and the sunny Kanto region and west are at temperatures typical of this time of year.

2025/12/10 08:05

Kesa is becoming increasingly cold from western to eastern Japan due to the effects of cold air in the upper atmosphere and radiation cooling.
As of 7 o'clock, the lowest temperatures observed were -3.3c in Sapporo, 1.7c in Sendai, 4.0c in Tokyo, 3.3c in Nagoya, 5.8c in Kanazawa, 4.8c in Osaka, 4.1c in Kochi, and 5.9c in Fukuoka, making it the lowest temperature of the season at 73 locations.



The expected maximum temperature during the day is Sapporo: 1c, Sendai: 8c, Tokyo: 14c, Nagoya: 13c, Kanazawa: 11c, Osaka: 14c, Kochi: 16c, Fukuoka: 15c.

Sunshine will reach western Japan, the Tokai region, and the Kanto region, which are covered by high pressure, and temperatures will be typical of this time of year. In sunny areas, you can feel the warmth of the sunlight. There will be a large difference in temperature between morning and evening and during the day, so please take care of your health by adjusting your clothing accordingly.
In northern Japan, where the effects of cold air remain, the temperature will not rise, and it will likely be as cold as midwinter. Please take all possible measures to protect yourself from the cold.

Today's weather (Wednesday, the 10th): Calm and sunny from Kanto to the west; rain and snow on the Sea of ??Japan side of northern Japan and Hokuriku

2025/12/10 06:30

Today, the 10th (Thursday), the weather will continue to be prone to rain and snow due to the effects of cold air, mainly in northern Japan. On the other hand, many places west of the Kanto region, which is covered by high pressure, are expected to have mild skies.



On the Sea of Japan side of northern Japan, clouds tend to spread, and there will be places where it will snow. In coastal areas, winds are strong and there is a possibility of blowing snow, so be careful of poor visibility. The area of snow will gradually shrink in the afternoon, but in Hokkaido, snow is likely to start falling again on the Japan Sea side towards the end of the night.
Although there are many areas on the Pacific side of northern Japan that receive sunlight, there is a possibility of showers in areas such as Tohoku, so please be careful of changes in the sky.

The weather in Hokuriku is likely to be rainy around noon. Please be careful of lightning strikes and gusts of wind as there is a risk of localized thunderstorms.

It will be mild and sunny from the Kanto region to western Japan, which is covered by high pressure. The temperature during the day is typical of this time of year, and you can feel warm under the sunshine.

[Gemid Meteor Shower 2025] "Conditions are good" without the influence of moonlight; "stormy" weather forecast

2025/12/09 15:47

The Geminid meteor shower is one of the three major meteor showers that reaches its peak in December every year.

A large number of meteors can be seen almost every year, so it can be said that
is the largest meteor shower of the year.

When conditions are good and an experienced observer observes the meteors, it is not uncommon to see around 100 meteors per hour.

This year, the conditions are favorable for
observations as there is almost no influence from moonlight.

If you are near Tokyo, you may be able to see up to 50 meteors per hour.



The peak of the meteor shower (when the meteor shower itself is most active) is around 5:00 pm on the 14th (Sunday), and from the night of the 13th (Saturday) to the morning of the 14th (Sunday) and from the night of the 14th (Sunday) to the morning of the 15th (Monday), it is likely that more meteors than usual will be seen.

The moonlight and other conditions are good, but
stormy weather is expected this weekend, so the weather conditions don't seem to be good.




Looking at the forecast weather map for Saturday and Sunday, the low pressure system accompanied by a front is expected to advance near the Korean Peninsula on the 13th (Saturday), and the low pressure system is expected to continue to develop and pass near Honshu on the 14th (Sunday).

This Saturday and Sunday, the rain will spread from the west, and the weather is likely to become stormy with strong rain and wind across the country until the 14th (Sunday).



Forecast for snow, rain and wind at 6pm on Sunday 14th.

The so-called maximum night, when the most shooting stars can be seen, is expected to occur from the night of Sunday the 14th to the early morning of Monday the 15th, but on the night of Sunday the 14th, it is likely that there will be snow and rain in some places, mainly in Tohoku and Hokuriku.

Winds will be strong across the country, with cold winds from the north.

On the Pacific side of western and eastern Japan, there are likely to be places where the clouds have cleared and
meteors can be seen, but
the wind is likely to feel quite cold.

When observing the meteor shower, it is best to wear clothing that protects you from the wind and cold.




It is expected that quite a lot of meteors will be visible from the night of the 13th (Saturday) to the morning of the 14th (Sunday), the day before the maximum night.

If you observe in a dark place with a dark sky, you can expect to see about 40 to 45 meteors per hour from 0:00 to 4:00 on the 14th.
In northern Japan and Hokuriku, there may be places where it is easier to observe it on the night of the 13th (Saturday), the day before
, than on the 14th (Sunday).




Meteors appear radially around the radiant point, but
they can appear not only near the radiant point but also in either direction, so
try to look over as wide a area of the sky as possible.

Also, it is a good idea to continue observing for at least 15 minutes until your eyes adjust to the darkness outside.

You can observe from a comfortable position by lying down on the ground on a leisure sheet or
sitting on a chair with a tiltable backrest.

However, it will be cold, so
please take precautions against the cold when observing.
Also, be careful not to get into an accident,
and observe good manners.

Friday: Stormy weather on the Sea of ??Japan side of northern Japan Widespread stormy weather as low-pressure system develops over the weekend 10 degrees Celsius expected in central Tokyo

2025/12/09 12:26

Weekly Weather Forecast
#High pressure in the west and low in the east in short cycles
#12th (Friday): Stormy weather on the Sea of Japan side of northern Japan due to winter-type pressure distribution
#Low pressure system will develop and pass through the weekend Widely stormy weather in western and northern Japan
#Maximum temperature expected to be 10c in the city center on the weekend



#Pressure pattern with high pressure in the west and low pressure in the east in short cycles
Over the next week, the pressure pattern will have high pressure in the west and low pressure in the east in short cycles, and cold air will move southward.
Tomorrow, the 10th (Wednesday), high pressure is expected to move near Japan, and the pressure pattern of high in the west and low in the east is expected to loosen.
Cold air with temperatures below -6c at around 1,500m above the ground will move north toward the Tsugaru Strait.
It is expected to snow intermittently on the Sea of Japan side of northern Japan.
The next day, on the 11th (Thursday), the low pressure system will move into the Sea of Okhotsk, and another low pressure system with another front will pass near the Tsugaru Strait and move off the coast of Kushiro.
A cold front extending from a low pressure system will pass from western Japan to the Tohoku region, and is expected to cause rain in western Japan and Hokuriku, rain and snow in Tohoku, and snow in Hokkaido.
After the passage of the low pressure system, the pressure will gradually become winter-like, with high pressure in the west and low pressure in the east.
Cold air with temperatures below -6c at an altitude of around 1500m is expected to move south toward the Sea of Japan side of eastern Japan.

#Friday the 12th: Stormy weather will occur on the Sea of Japan side of northern Japan due to winter-like pressure distribution



On Friday the 12th, there will be a winter-like pressure distribution.
Wet snow is expected to fall in the San'in region and northern Kinki region, and snow is expected to fall in places along the mountains of northern Gifu and Nagano prefectures, northern Kanto, Hokuriku, and the Sea of Japan side of northern Japan.
Winds are increasing across the country, and especially in Hokuriku and the Sea of Japan side of northern Japan, there will be stormy winds, blowing snow, and rough weather.
Depending on the strength of the winter-like air pressure distribution, there is a risk of severe storms.

#Over the weekend, a developing low pressure system will pass near Japan, causing widespread stormy weather across western and northern Japan



Over the weekend, a low pressure system will develop and pass near Japan, causing severe weather over a wide area.
On the 13th (Saturday), a low pressure system will move toward the western Sea of Japan, and rain is expected to occur from Okinawa to western Japan, with snow expected to fall in places on the Sea of Japan side of northern Japan.
On the 14th (Sunday), a low pressure system will move toward the coast of Sanriku.
It is expected to rain widely from Okinawa to Tohoku, with some snow mixed in along the mountains in northern Gifu prefecture, northern Nagano prefecture, northern Kanto, Hokuriku and Tohoku.
There are probably places in Hokkaido where it snows.
Due to the developing low pressure system, there is a risk of widespread rain, snow, and strong winds, leading to stormy weather.
Please pay attention to the latest information.
After this low pressure system moves eastward, the winter-like pressure pattern will become stronger.





#Weekend maximum temperature expected to be 10c in central Tokyo
On the 11th (Thursday), there will be many places where the temperature is higher than normal.However, from the 12th (Friday) to the 13th (Saturday), there will be many places where the temperature will be lower than normal due to the lingering influence of winter-like atmospheric pressure patterns and cold air.
On Saturday the 13th, the maximum temperature in the city is expected to be 10c.
Please take proper measures to protect yourself from the cold so that you do not get sick due to daily temperature changes.