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Monthly Highlights on the Climate System

'Monthly Highlights on the Climate System' has been issued since March 2007 as a monthly bulletin focusing on the monthly highlights of the monitoring results.

Notice: Products have been upgraded from PDF to HTML format starting from the issue of May 2025 for improved accessibility.

Highlights in June 2025

- Sea surface temperature anomalies in the equatorial Pacific were negative from the central to the eastern parts and significantly positive in the western part. NINO.3 was -0.2°C. Remarkably positive anomalies prevailed in the middle latitudes of the North Pacific and the equatorial Indian Ocean.
- Convection was more active than normal in the northwestern India, from the Bay of Bengal to the east of Philippines and around the Indonesia, which meant stronger-than-normal activities of Asian monsoon.
- In the upper troposphere, a pair of anti-cyclonic circulation anomalies were observed over the northern and southern Indian Ocean, while cyclonic circulation anomalies was observed in the subtropical latitudes of the North Pacific, which meant that both the Tibetan high and the mid-Pacific trough were stronger than normal. In the Northern Hemisphere, a wavy anomaly pattern was dominant along the northward-shifted subtropical jet and remarkably anti-cyclonic anomalies was observed around Japan.
- In the lower troposphere, cyclonic circulation anomalies were observed from India to the subtropical northwestern Pacific and monsoon westerlies were stronger than normal, while subtropical highs over the North Pacific and the North Atlantic were stronger than normal. The extension of the North Pacific subtropical high toward Japan was stronger than normal.
- The monthly anomaly of the average surface temperature over Japan was +2.34°C which was the warmest record for June since 1898. Monthly mean temperatures were significantly above normal in northern/eastern/western Japan, with the highest on record for June since 1946 and above normal in Okinawa/Amami. Monthly precipitation amounts were significantly below normal in Okinawa/Amami and below normal on the Pacific side of northern/western Japan. Monthly sunshine durations were significantly above normal on the Pacific side of northern/eastern/western Japan and Okinawa/Amami and above normal on the Sea of Japan side of northern/eastern/western Japan.

Climate in Japan (Fig. 1):

- Monthly mean temperatures were significantly above normal in northern/eastern/western Japan, with the highest on record for June since 1946 and above normal in Okinawa/Amami, because warm air covered nationwide.
- The monthly anomaly of the average surface temperature over Japan was +2.34°C (the warmest for June since 1898) . On a longer time scale, the average surface temperatures have risen at a rate of about 1.44°C per century in June.
- Monthly precipitation amounts were below normal on the Pacific side of northern/western Japan, due to weak influence of fronts and moist air inflow.
- Monthly sunshine durations were significantly above normal on the Pacific side of northern/eastern/western Japan and above normal on the Sea of Japan side of northern/eastern/western Japan. The regions were not significantly affected by fronts and moist air inflow. In Okinawa/Amami, monthly precipitation amounts were significantly below normal and monthly sunshine durations were significantly above normal because the Pacific High covered the region.

World Climate:

- The monthly anomaly of the global average surface temperature (i.e., the combined average of the near-surface air temperature over land and the SST) was +0.38°C (3rd warmest for June since 1891) (preliminary value) (Fig. 2). On a longer time scale, global average surface temperatures have risen at a rate of about 0.76°C per century in June (preliminary value).
- Extreme climate events were as follows (Fig. 3).
  - Monthly mean temperatures were extremely high from Kamchatka Peninsula to eastern China, from western Mongolia to eastern Turkmenistan and from the UK to around the Mediterranean Sea.
  - Monthly mean temperatures were extremely low in and around northern Argentina.
  - Monthly precipitation amounts were extremely high in and around southern Mexico.
  - Monthly precipitation amounts were extremely low from Turkey to western Europe.

Oceanographic Conditions:

- In the equatorial Pacific, negative SST anomalies were observed from the central to eastern parts except to the west of South America, and remarkably positive SST anomalies were observed in the western part (Fig. 4). Both the monthly mean SST anomaly averaged over the NINO.3 region and the SST deviation from the latest sliding 30-year mean over the region were -0.2°C (Fig. 5).
- In the North Pacific, remarkably positive SST anomalies were observed in the western to central parts from the tropics to the mid-latitudes, and remarkably negative SST anomalies were observed to the southwest of California.
- In the South Pacific, remarkably positive SST anomalies were observed in the western part, and in the central part of the mid-latitudes.
- In the equatorial Indian Ocean, remarkably positive SST anomalies were observed in the equator. Remarkably negative SST anomalies were observed in the western Arabian Sea and the South China Sea.
- In the Atlantic, remarkably positive SST anomalies were observed in the Northern Hemisphere mid-latitudes, and remarkably negative SST anomalies were observed in the central part of the equator.

Tropics:

- Convective activity was enhanced over northwestern India, from the Bay of Bengal to the east of the Philippines, around the Maritime Continent and Central America, and suppressed from the Atlantic to the western Indian Ocean and over the equatorial central Pacific (Fig. 6). The overall activity over the Asian monsoon convection was stronger than normal.
- The active phase of equatorial intraseasonal oscillation propagated eastward from the Pacific to the Atlantic in the first half of June, and the amplitude became small afterward (Fig. 7).
- In the upper troposphere, anti-cyclonic circulation anomalies straddling the equator were seen around the Maritime Continent. A wavy anomaly pattern was seen along the subtropical jet, with anti-cyclonic circulation anomalies over the western Middle East, north of Pakistan and from Japan to the east, and cyclonic circulation anomalies over western China. The Tibetan high and the mid-Pacific trough were stronger than normal. Anti-cyclonic circulation anomalies were seen from the eastern USA to the mid-latitude North Atlantic (Fig. 8).
- In the lower troposphere, cyclonic circulation anomalies straddling the equator were seen from the eastern Indian Ocean to the Maritime Continent. Both the northward extension of the North Pacific and the North Atlantic subtropical highs were stronger than normal (Fig. 9).
- In the sea level pressure field, positive anomalies were seen over a wide area of the equator, and negative anomalies were seen over the Middle East, the South China Sea and to the east of the Philippines. The Southern Oscillation Index value was +0.7 (Fig. 5).

Extratropics:

- In the 500-hPa height field (Fig. 10), the tropospheric polar vortex split into three parts along the East Siberian coast, near Iceland, and near the Baffin Island. Positive anomalies were seen in most of the Northern Hemisphere mid-latitudes, and remarkably positive anomalies were seen over southern Europe, from around Tibet to Western and Central Siberia, and from the East China Sea to the central North Pacific.
- The subtropical jet stream shifted southward over China, while the westerly jet stream shifted remarkably northward from Japan to the North Pacific, compared to its normal position (Fig. 11). The polar-front jet stream meandered over northern Eurasia.
- In the sea level pressure field (Fig. 12), positive anomalies were seen over the mid-latitude North Pacific and North Atlantic, and the extension of the North Pacific subtropical high toward over Japan was stronger than normal. Negative anomalies were seen over the northern North Atlantic, Western Russia, and from Eastern Siberia to the Sea of Okhotsk.
- Temperatures at 850-hPa were below normal over northeastern Africa, India, the East Siberian Sea, and the subtropical North Atlantic, remarkably positive anomalies over southern Europe, from around Tibet to Western and Central Siberia, and from the East China Sea to the central North Pacific (Fig. 13).

Zonal mean:

- In the zonal mean zonal wind in the troposphere, westerly anomalies were seen in the latitude bands of 50°N and 40-50°S, and easterly anomalies were seen in the latitude bands of 30°N and 30°S.
- The zonal mean temperatures in the troposphere were above normal in most areas.

Supplemental information

- Climate Anomaly Table over Japan
- Extratropics in the Southern Hemisphere
- Snow in the Northern Hemisphere
- Arctic sea ice (link to the National Snow and Ice Data Center)

Fig.1 Monthly climate anomaly/ratio over Japan (June 2025) Top: temperature anomalies (degree C) Middle: precipitation ratio (%) Bottom: sunshine duration ratio (%) The base period for the normal is 1991-2020.

Fig.10 Monthly mean 500-hPa height and anomaly in the Northern Hemisphere (June 2025) The contours show 500-hPa height at intervals of 60 m. The shading indicates its anomalies. The base period for the normal is 1991-2020.	Fig.11 Monthly mean 200-hPa wind speed and vectors in the Northern Hemisphere (June 2025) The black lines show wind speed at intervals of 10 m/s. The brown lines show its normal at intervals of 20 m/s. The base period for the normal is 1991-2020.
Fig.12 Monthly mean sea level pressure and anomaly in the Northern Hemisphere (June 2025) The contours show sea level pressure at intervals of 4 hPa. The shading indicates its anomalies. The base period for the normal is 1991-2020.	Fig.13 Monthly mean 850-hPa temperature and anomaly in the Northern Hemisphere (June 2025) The contours show 850-hPa temperature at intervals of 3 degree C. The shading indicates its anomalies. The base period for the normal is 1991-2020.

Back Number

The descriptions from May-2011 to April-2021 issue are based on the former climatological normal (1981-2010 average).
In the descriptions until April-2011 issue, 1979-2004 average is used as climatological normal unless otherwise stated.
The descriptions until January-2014 issue are based on the JRA-25/JCDAS datasets.
The descriptions from February-2014 to April-2023 issue are based on the JRA-55 reanalysis.

Figures and Tables

Notice: Products based on JRA-3Q were updated to those with improved quality in terms of tropical cyclone analysis. OLR-related products from January 1991 are based on NOAA CPC Blended OLR (CBO).

Notice: Figures of 'Atmospheric Circulation', 'Time Cross Section', and 'Indices' have been revised with improved quality data regarding tropical cyclone analysis. (18 June 2024)

Notice: Depending on the availability of NOAA CPC Blended OLR (CBO) data, updates may be delayed or figures may be filled with gray indicating data missing.

• Explanation on the Products for Climate System Monitoring
• 5-day Mean Figures
• 10-day Mean Figures
• Monthly Mean Figures
• 3-month Mean Figures
• Time Cross Sections
• Indices
• Oceanic Figures and Tables