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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 July 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 -0.1°C. Remarkably positive anomalies prevailed in the middle latitudes of the North Pacific and the equatorial Indian Ocean, while negative anomalies prevailed in the western Arabian Sea and the South China Sea. Negative anomalies were observed from the northern Mariana Islands to the southern Ogasawara Islands.
- Convective activity in the subtropical western North Pacific was at a record high. Convective activities accompanied with the Asian monsoon were more active than normal and significantly northeastward shifted.
- In the upper troposphere, the subtropical jet was remarkably northward shifted compared to its normal position in the Northern Hemisphere. The Tibetan high was stronger than normal and extended strongly towards the Far East. The mid-Pacific trough was also stronger than normal and spread west to the southern China.
- In the lower troposphere, cyclonic circulation anomalies were observed from India to the subtropical western North Pacific and the deeper-than-normal monsoon trough was located eastward compared to its normal position. Equatorial zonal winds over the Indian Ocean and the Pacific were westerly anomalies and easterly anomalies, respectively.
- In the 500-hPa height field, the polar vortex was located in the northern Greenland and the summer Arctic Oscillation (AO) index was positive. Positive anomalies covered almost mid-latitudes and significantly from the central Asia to the western Pacific, especially around the northern Japan whose normalized anomalies were over +3.
- The monthly anomaly of the average surface temperature over Japan was +2.89°C which was the warmest record for July since 1898. Monthly mean temperatures were significantly above normal in northern/eastern/western Japan, with the highest on record for July since 1946 while below normal in Okinawa/Amami. Monthly precipitation amounts were significantly below normal on the Sea of Japan side of northern/eastern/western Japan and the Pacific side of northern Japan, while significantly above normal over Okinawa/Amami. Monthly sunshine durations were significantly above normal in northern/eastern/western Japan while significantly below normal over Okinawa/Amami.

Climate in Japan (Fig. 1):

- Monthly mean temperatures were significantly above normal in northern/eastern/western Japan, with the highest on record for July since 1946. This was due to the regions being covered by warm air associated with the subtropical jet stream, which was located significantly further north than usual over eastern Asia, and also due to the North Pacific Subtropical High (NPSH), which extended over Honshu, bringing sunny and hot days to the regions.
- The monthly anomaly of the average surface temperature over Japan was +2.89°C (the warmest for July since 1898) . On a longer time scale, the average surface temperatures have risen at a rate of about 1.38°C per century in July.
- Monthly precipitation amounts were significantly below normal on the Sea of Japan side of northern/eastern/western Japan and on the Pacific side of northern Japan, due to the weak influence of the Baiu front. Those on the Sea of Japan side of eastern Japan were the smallest on record for July since 1946.
- Monthly sunshine durations were significantly above normal on the Sea of Japan and Pacific sides of northern/eastern/western Japan, because the regions were frequently covered by the NPSH. Those on the Sea of Japan of eastern/western Japan were the longest on record for July since 1946.
- In contrast, in Okinawa/Amami, monthly precipitation amounts were significantly above normal and monthly sunshine durations were significantly below normal, due to the influence of typhoons and wet air inflow.

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 +0.42°C (3rd warmest for July since 1891) (preliminary value) (Fig. 2). On a longer time scale, global average surface temperatures have risen at a rate of about 0.75°C per century in July (preliminary value).
- Extreme climate events were as follows (Fig. 3).
  - Monthly mean temperatures were extremely high from southern Eastern Siberia to southern Central Asia via East Asia, in central Southeast Asia, from the northwestern Middle East to northern Europe via northwestern Northern Africa and in and around Colombia.
  - Monthly precipitation amounts were extremely high from Okinawa/Amami region of Japan to southeastern China, from eastern Europe to northern Algeria, in northern Argentina and in southeastern Australia.

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). The monthly mean SST anomaly averaged over the NINO.3 region was 0.0°C and the SST deviation from the latest sliding 30-year mean over the region was -0.1°C (Fig. 5).
- In the North Pacific, remarkably positive SST anomalies were observed in the western part of the tropics and across a wide range of the mid-latitudes, and remarkably negative SST anomalies were observed to the south of Japan.
- In the South Pacific, remarkably positive SST anomalies were observed in the western and central parts, and in the eastern part of the subtropics.
- In the tropical Indian Ocean, remarkably positive SST anomalies were observed except for the western part. 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 western subtropics and eastern mid-latitudes of the Northern Hemisphere and in the western part of the equator, and remarkably negative SST anomalies were observed in the eastern part of the equator.

Tropics:

- Convective activity was enhanced over northwestern India, from the Philippines to the subtropical western North Pacific and over the eastern Maritime Continent, and suppressed from the Bay of Bengal to the southern South China Sea and from the eastern Pacific to Africa via the Atlantic (Fig. 6). The overall activity over the Asian monsoon convection was stronger than normal, with a significant northeastward shift.
- The active phase of equatorial intraseasonal oscillation saw small amplitude in the first half of July, followed by eastward propagation from around the Maritime Continent to the Atlantic via the Pacific (Fig. 7).
- In the upper troposphere, anti-cyclonic circulation anomalies straddling the equator were seen around the Maritime Continent. Anti-cyclonic circulation anomalies were seen from north of Pakistan to Japan via China, and cyclonic circulation anomalies were seen from the mid-latitude North Pacific to southern China, corresponding to the stronger-than-normal Tibetan high and the mid-Pacific trough (Fig. 8).
- In the lower troposphere, cyclonic circulation anomalies straddling the equator were seen from the Indian Ocean to the western Pacific. Significant cyclonic circulation anomalies were seen from the South China Sea to the east of the Philippines, and the northward extension of the North Pacific subtropical high was stronger than normal. Anti-cyclonic circulation anomalies straddling the equator were seen in the Pacific (Fig. 9).
- In the sea level pressure field, positive anomalies were seen over a wide area of the equator, and negative anomalies were seen from the western Middle East to the east of the Philippines via the Indian Ocean. The Southern Oscillation Index value was +0.9 (Fig. 5).

Extratropics:

- In the 500-hPa height field (Fig. 10), the polar vortex was stronger than normal over northern Greenland. Positive anomalies were seen over a wide area in the mid-latitude Northern Hemisphere, with the significant anomalies over northern East Asia.
- The subtropical jet stream shifted northward with the hemispheric scale in the Northern Hemisphere, particularly over East Asia (Fig. 11). The polar-front jet stream over Eurasia meandered northward over northern Europe and Eastern Siberia, and southward over Western Siberia.
- In the sea level pressure field (Fig. 12), positive anomalies were seen over a wide area from the North Pacific to North America, and negative anomalies were seen around Greenland and over Eurasia. Significantly negative anomalies were seen to the south of Japan, and the extension of the North Pacific subtropical high toward Japan was stronger than normal.
- Temperatures at 850-hPa were above normal over northern Europe, the East Siberian Sea, and a wide area of mid-latitude Eurasia, and below normal from northern Canada to the western USA (Fig. 13).

Zonal mean:

- In the zonal mean zonal wind in the troposphere, the subtropical jet stream in the Northern Hemisphere significantly shifted poleward. The subtropical jet stream in the Southern Hemisphere shifted equatorward.
- The zonal mean temperatures in the troposphere were above normal except in the high-latitude Southern Hemisphere.

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 (July 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 (July 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 (July 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 (July 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 (July 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