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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 changed from PDF to HTML format starting from the issue of May 2025 for improved accessibility.

Highlights in July 2026

- In the tropical Pacific, sea surface temperature (SST) anomalies were significantly positive east of the dateline (Fig. 4). The NINO.3 index reached +2.5°C, tying the 1997 record for July (Fig. 5). Meanwhile, negative SST anomalies prevailed in the western tropical Pacific, except in a few regions. Significantly positive SST anomalies were also observed between 40°N and 50°N, except off the coast of North America, while negative SST anomalies prevailed between 30°N and 35°N in the North Pacific. In the tropical Indian Ocean, positive SST anomalies dominated, except in the central part between the equator and 20°S, where negative anomalies were observed.
- In the tropics, convective activity was significantly enhanced from the central to the eastern Pacific, while it was significantly suppressed from Africa to the western Pacific through the Indian Ocean and the Maritime Continent (Fig. 6).
- In the tropical upper troposphere, pairs of anticyclonic and cyclonic anomalies straddling the equator were observed over the tropical Pacific and across a broad region extending from South America through Africa and the Indian Ocean to the Maritime Continent, respectively (Fig. 8).
- In the tropical lower troposphere, pairs of cyclonic anomalies straddling the equator were observed from the western to the central Pacific. In the subtropical northwestern Pacific, cyclonic anomalies prevailed far southeast of Japan, while weak anticyclonic anomalies were observed over the South China Sea (Fig. 9). The Southern Oscillation Index (SOI) was -3.7 (Fig. 5).
- In the Northern Hemisphere, the polar front jet stream was significantly stronger than normal along the Arctic coast. The zonal-mean subtropical jet stream was slightly stronger than normal near 30°N and 60°N, while it was significantly weaker than normal between 40°N and 45°N. The subtropical jet stream was displaced slightly northward from its climatological position (Fig. 11).
- In the 500-hPa height field (Fig. 10), a stronger-than-normal polar vortex was located over the Arctic Ocean. In the high latitudes, positive height anomalies prevailed except over the Arctic Ocean. In the mid-latitudes, positive height anomalies also prevailed, with significantly positive anomalies observed over western Europe, around Japan, and southern North America, except in some regions.
- In the sea level pressure (SLP) field (Fig. 12), significantly negative anomalies were observed over the Arctic Ocean, indicating the positive phase of the summer Arctic Oscillation (AO). Significantly positive anomalies prevailed over the northern North Atlantic and south of the Aleutian Islands, while significantly negative anomalies were observed over China.
- Monthly mean temperatures were significantly above normal in northern, eastern, and western Japan and near normal in Okinawa/Amami (Fig. 1). The monthly mean surface air temperature anomaly averaged over Japan was +1.66°C, the fourth highest for July since 1898. Precipitation amounts were above normal in northern Japan and below normal in eastern and western Japan and Okinawa/Amami. Sunshine duration was near normal in northern Japan, while they were above normal in the other regions, with significantly above-normal values on the Sea of Japan side of western Japan and in Okinawa/Amami.

Climate in Japan (Fig. 1):

- Monthly mean temperature was significantly above normal in northern/eastern/western Japan, because the regions were covered by warm air associated with the subtropical jet stream located further north than usual over Japan. The monthly anomaly of the average surface temperature over Japan was +1.66°C (4th warmest for July since 1898). On a longer time scale, the average surface temperatures have risen at a rate of about 1.42°C per century in July.
- Monthly precipitation amounts were above normal on the Sea of Japan side of northern Japan and on the Pacific side of northern Japan, due to low-pressure systems, active Baiu-fronts and moist air inflow.
- Monthly precipitation amounts were below normal on the Sea of Japan side of eastern/western Japan, on the Pacific side of eastern/western Japan and in Okinawa/Amami. Monthly sunshine durations were significantly above normal on the Sea of Japan side of western Japan and in Okinawa/Amami, and above normal on the Sea of Japan side of eastern Japan and on the Pacific side of eastern/western Japan, because high-pressure systems frequently covered these regions.

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 +0.61°C (the 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 0.76°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 western Japan, from western East Asia to eastern Central Asia, in and around southern India, from the Indochina Peninsula to western Indonesia, from western Europe to the western Mediterranean region, in Western Africa, from southern Canada to the southwestern USA, from the Florida Peninsula to Mexico, in northeastern South America and from Peru to central Chile via southern Brazil.
  - Monthly precipitation amounts were extremely high in and around southwestern Russia and in northern Argentina.
  - Monthly precipitation amounts were extremely low from eastern to western Europe and from the eastern USA to the Gulf of Mexico region.

Oceanographic Conditions:

- In the tropical Pacific, significantly positive SST anomalies were observed east of the dateline (Fig. 4). The monthly mean SST anomaly averaged over the NINO.3 region was +2.6°C and the SST deviation from the latest sliding 30-year mean over the region was +2.5°C (Fig. 5). In the western tropical Pacific, negative SST anomalies were observed except in some areas, including the region north of New Guinea.
- In the North Pacific, significantly positive SST anomalies were observed in the subtropics, except around Hawaii, and in the latitudinal bands of 40°-50°N, except off the coast of North America.
- In the South Pacific, positive SST anomalies were widely observed, except in the central subtropical region. Significant positive anomalies were observed in the eastern South Pacific and around New Zealand.
- In the Indian Ocean, positive SST anomalies prevailed over most areas, with significant positive anomalies in some regions.
- In the North Atlantic, significantly positive SST anomalies were observed in the eastern part and along the latitudinal band between 20°N and 30°N, while negative anomalies were observed in the western mid-latitudes.
- In the South Atlantic, positive SST anomalies were widespread, except off the west coast of Africa in the tropics and subtropics, with significant positive anomalies observed in the mid-latitudes.

Tropics:

- Convective activity was extremely enhanced from the central to the eastern Pacific, while it was strongly suppressed from Africa to the western Pacific through the Indian Ocean and the Maritime Continent (Fig. 6). The anomaly pattern of large-scale divergence in the upper troposphere clearly exhibited a wave number-1 structure. The eastward propagation of the active convective phase associated with the equatorial intraseasonal oscillation was unclear (Fig. 7).
- In the upper troposphere, paired anticyclonic circulation anomalies straddling the equator were observed over the Pacific, while paired of cyclonic circulation anomalies were dominant from South America to the Maritime Continent via Africa and the Indian Ocean (Fig. 8).
- In the lower troposphere, pronounced paired cyclonic circulation anomalies prevailed from the western to the central Pacific, accompanied by dominant westerly wind anomalies along the equator. Meanwhile, paired weak anticyclonic circulation anomalies straddling the equator were seen over the Indian Ocean (Fig. 9). In the subtropical western North Pacific, cyclonic circulation anomalies dominated southeast of Japan, whereas weak anticyclonic circulation anomalies were observed over the East China Sea.
- In the sea level pressure field, pronounced positive anomalies were observed from the Indian Ocean to the Maritime Continent, while negative anomalies prevailed from the central to the eastern tropical Pacific. The Southern Oscillation Index (SOI) was -3.7 (Fig. 5).

Extratropics:

- In the 500‑hPa height field (Fig. 10), the polar vortex was centered in the Arctic Ocean, and positive anomalies were seen except for negative anomalies from the Arctic Ocean to northern Europe and around Alaska in the high latitudes. In the Northern Hemisphere mid-latitudes, positive anomalies were seen except over western Russia, with the significant positive anomalies over western Europe, around Tibet, Japan, south of the Aleutian Islands and over southern North America.
- The westerly jet stream was slightly displaced northward over Eurasia and split into two branches over the Pacific, where the westerlies were stronger than normal around 30°N and 50°N (Fig. 11).
- In the sea level pressure field (Fig. 12), significant negative anomalies were observed along the Arctic Ocean, and the positive phase of Arctic Oscillation prevailed. Significant positive anomalies were observed over the northern North Atlantic and the south of the Aleutian Islands, while significant negative anomalies were observed around China.
- In the 850‑hPa temperature field (Fig. 13), the anomaly pattern closely resembled that of the 500-hPa height field, except for negative temperature anomalies to the east of Japan.

Zonal mean:

- In the zonal-mean zonal wind in the troposphere, the subtropical jet stream in the Northern Hemisphere was significantly intensified around 30°N and 60°N. The polar front jet stream was strong around 80°N.
- The zonal mean temperatures in the troposphere were above normal over a wide area in the Northern Hemisphere, with significantly above-normal temperatures between 50°N and 70°N.

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 2026) Top: temperature anomalies (°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 2026) 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 2026) 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 2026) 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 2026) The contours show 850-hPa temperature at intervals of 3 °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