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HOME >Climate System Monitoring > Monthly Highlights on the Climate System

Monthly Highlights on the Climate System

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

Highlights in May 2024

- Oceanic and atmospheric conditions over the equatorial Pacific indicate that the El Niño event which had persisted since boreal spring 2023 is likely to have ended (see El Niño Outlook updated on 10 June 2024).
- Monthly mean temperatures were above normal in northern/eastern Japan and Okinawa/Amami. Monthly precipitation amounts were significantly above normal on the Pacific side of eastern/western Japan.
- Convective activity was enhanced over the tropical Indian Ocean and suppressed near the Philippines. In the lower troposphere, anti-cyclonic circulation anomalies were seen from the Indochina Peninsula to the east of the Philippines, effectively bringing humid air to the areas west of eastern Japan.
- In the 500-hPa height field, zonally-elongated positive anomalies were dominant in the mid-latitude North Pacific including Japan, and a trough was seen to the west of Japan. These atmospheric conditions resulted in above normal temperatures and above normal precipitation amounts over a wide area of Japan.

Full version (PDF)

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)

If you would like to subscribe to Monthly Highlights on the Climate System, please send an email to

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Tokyo Climate Center, Climate Prediction Division.
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