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.

Notice: From 19 May 2021 onward, the products in this page are based on the new climatological normal (1991-2020 average) unless otherwise stated.

Highlights in April 2023

- ENSO-neutral conditions continued in April (see El Niño Outlook updated on 12 May 2023).
- Monthly mean temperature were significantly above normal in northern and eastern Japan. Monthly mean temperatures in northern Japan tied with 1983 as the highest on record for April since 1946.
- Monthly mean temperatures were extremely high in and around the Indochina Peninsula, from southwestern Europe to the northwestern part of Northern Africa, from central Peru to northern Chile. Monthly mean temperatures were extremely low in and around Alaska.
- Convective activity was enhanced over the latitude band of 10°-20°N from the western to central North Pacific and over the seas northwest of Peru, suppressed over the eastern tropical Indian Ocean and near the date line in the equatorial Pacific.
- In the 500-hPa height field, a wavy anomaly pattern was seen from the central North Atlantic to Japan via Siberia with positive anomalies over northern Europe and negative anomalies from southern Central Siberia to northwestern East Asia. Positive anomalies were seen from southern China to the mid-latitude North Pacific and over Eastern Siberia.
- The subtropical jet stream shifted southward from its normal position from Africa to India, and was weaker than normal over Japan. The polar front jet stream meandered southward over northern East Asia.

Full version (PDF)

Monthly Highlights on the Climate System (April 2023)
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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.

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Tokyo Climate Center, Climate Prediction Division.
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