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 December 2024

- ENSO-neutral conditions persisted, but overall conditions in the atmosphere and ocean were similar to those of La Niña events. Convective activity was enhanced from the eastern Indian Ocean to Southeast Asia, and suppressed from the western equatorial Indian Ocean and in and around the central tropical Pacific.
- In the upper troposphere, corresponding to the convective activity, anti-cyclonic circulation anomalies straddling the equator were seen from the Indian Ocean to near Southeast Asia, and cyclonic circulation anomalies straddling the equator were seen from the central to eastern Pacific. A wavy anomaly pattern was seen from southern China to the North Pacific with cyclonic circulation anomalies from Japan to the east.
- In the 500-hPa height field, a part of the split polar vortex was displaced southward and zonally extended from southern Eastern Siberia to the Aleutian Islands. A wave train was seen from Siberia to Japan.
- In the sea level pressure field, the Aleutian Low and the Siberian High were both stronger than normal, resulting in the intensified East Asian winter monsoon.
- Monthly mean temperatures were below normal in northern Japan due to cold-air inflow.
- Monthly precipitation amounts were significantly above normal on the Sea of Japan side of eastern Japan and above normal on the Sea of Japan side of northern Japan. On the other hand, monthly precipitation amounts were the lowest on the Pacific side of western Japan and tied with 1973 as the lowest on the Pacific side of eastern Japan on record for December since 1946.

Full version (PDF)

Monthly Highlights on the Climate System (December 2024)
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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.

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.

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Tokyo Climate Center, Climate Prediction Division.
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