The marine heatwave bulletin provides forecasts and analysis of marine heatwave events across the globe and throughout the year. Used datasets include observations (satellite sea surface temperature maps) and numerical model analyses (assimilating satellite and in situ observations) to derive marine heatwave forecasts for a 10-day period. This week’s forecasts were produced using as a comparison the marine heatwave situation on 15/07/2025.
Key Takeaways For This Week
- Begining of a marine heatwave in the Norwegian Sea.
- Increasing extent and intensity of the marine heatwave in the eastern basin of the Mediterranean Sea.
- Decreasing marine heatwave activity along the Spanish and French coasts.
- Increasing marine heatwave intensity in Gulf of Mexico and south of Cuba.
- Increasing marine heatwave intensity in the Sea of Japan and the Sea of Okhotsk.
- Decreasing marine heatwave extent in the Bay of Bengal.
European Zone
North Atlantic
- The marine heatwave along the Spanish and French coasts is diminishing in size and intensity, with only a few areas remaining in the moderate category.
- In the North Sea, the heatwave remains stable.
- In the Norwegian Sea, a marine heatwave of moderate to strong category has set in.
Mediterranean Sea
In the western basin, the surface and intensity of the marine heatwave decrease, leaving only a few areas affected by moderate categories. In the eastern basin, the extent of the marine heatwave is increasing, as well as its intensity, with the development of strong categories.
Global Ocean
North Atlantic
The area and intensity of the marine heatwave stretching from eastern Florida to the centre of the basin are decreasing, and most of it is now in moderate category.
Tropical Atlantic
The marine heatwave in the Gulf of Mexico and south of Cuba persists in extent and is intensifying, with the development of strong and severe categories.
North Pacific
The marine heatwave in the centre of the basin at around 30°N is increasing in size. Its intensity is decreasing in its eastern part, mainly in moderate category, and remains stable in its western part, in moderate to strong category, and locally severe to extreme.
The marine heatwave in the Sea of Japan and the Sea of Okhotsk is increasing in intensity, and is now mainly in strong to severe and locally extreme categories.
Indian Ocean
The marine heatwave in the central basin is decreasing in area, with its intensity remaining in the moderate and locally strong categories. The marine heatwave affecting the Bay of Bengal is receding, leaving only a small area affected by moderate to locally strong categories.
Weekly Temperature Anomalies
20 – 26 July 2025
| North Atlantic | -2°C to >3°C |
| Mediterranean Sea | 0.5°C to >2.5°C |
| Tropical Atlantic | -2°C to 2°C |
| North Pacific | -3°C < à >3°C |
| Indian Ocean | -3°C to 2.5°C |
Access the Daily Global Physical Bulletin for a 9-day forecast here.
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Notes
Datasets and products :
Global Ocean Physics Analysis and Forecast (sea surface temperature) E.U. Copernicus Marine Service/ Mercator Ocean International. https://doi.org/10.48670/moi-00016
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