The SEPRESS team has now released their forecast outlook for tropical cyclone (TC) activity in the Northwest Pacific, surface air temperature (SAT) in China, and global sea surface temperature (SST) for October 2025.

This month, the overall SAT in China is predicted to be above the climatological mean, with the most significant warming (>+1°C) in Northeast China, the Yangtze River Delta, and the Tibetan Plateau (Figure 1). For the global SST, the equatorial central–eastern Pacific is about 0.5–1.0°C lower than the average, indicating a weak to moderate La Niña signal, with the negative phase of the Indian Ocean Dipole (IOD) developing to its peak intensity. Meanwhile, the mid-latitude North Pacific, particularly the seas off the coast of China, will continue to experience anomalously warm SSTs (Figure 2).

Against this background, during the autumn-to-winter transition, cold and warm air masses throughout northern China are expected to become more active, leading to frequent sharp day-to-day temperature fluctuations (Figure 3). At the same time, TC frequency and intensity in the Northwest Pacific during October are expected to be close to the climatological mean. However, the warm SST anomalies along China’s eastern coastal seas, together with the westward displacement of the subtropical high, are likely to steer more TCs toward landfall in China, with an expected increase of about 35%. The TC track density anomaly consistently indicates a higher-than-average probability of TC impacts in regions from the Pearl River Estuary to coastal southern China, particularly in the Guangdong-Hong Kong-Macao Greater Bay Area (Figure 4).

In summary, China is forecast to remain generally warmer than the climatological mean in October, while northern China will experience more pronounced daily temperature variability, requiring early adjustments in production and disaster preparedness. TC impact risks remain elevated along China’s southeast coast in October. Stakeholders are advised to remain highly vigilant against disasters caused by frequent TC landfalls, including heavy rainfall, strong winds, and storm surges. Relevant departments are advised to implement preparedness measures in advance and strengthen TC monitoring and early warning systems. In addition, more attention should be paid to the subsequent evolution of La Niña and the IOD, as these will be critical for improving forecast accuracy for late autumn and the upcoming winter.

––––––––––––

The above monthly TC outlook is based on the SEPRESS Global Climate Seamless Prediction System. SEPRESS, or Seamless Prediction and Services for Sustainable Natural and Built Environments, is a global initiative led by the Hong Kong University of Science and Technology (HKUST) that translates scientific advancements in weather-to-climate (or, subseasonal-to-seasonal) prediction into practical, tailored solutions to enhance global climate resilience and sustainability. The initiative, endorsed by UNESCO, aims to bridge the gap between science and society by fostering partnerships and delivering actionable outcomes to support the UN’s Sustainable Development Goals. The SEPRESS team comprises hydrometeorologists and modelers from the HKUST, the Institute of Atmospheric Physics (Chinese Academy of Sciences), and Beijing Normal University.

Text and Figures contributed by: Dipendra LAMICHHANE, LI Shentong, SONG Yurong, ZHU Tao, ZHANG Shiyu

Revision by: CHENG Tat-Fan, Aubrey LIAO