In the summer of 2018, the Korea-Japan (KJ) region experienced an extremely severe and prolonged heatwave. This study examines the GloSea6 model's prediction performance for the 2018 KJ heatwave event and investigates how its prediction skill is related to large-scale circulation patterns identified by the k-means clustering method. Cluster 1 pattern is characterized by a KJ high-pressure anomaly, Cluster 2 pattern is distinguished by an Eastern European highpressure anomaly, and Cluster 3 pattern is associated with a Pacific-Japan pattern-like anomaly. By analyzing the spatial correlation coefficients between these three identified circulation patterns and GloSea6 predictions, we assessed the contribution of each circulation pattern to the heatwave lifecycle. Our results show that the Eastern European highpressure pattern, in particular, plays a significant role in predicting the evolution of the development and peak phases of the 2018 KJ heatwave approximately two weeks in advance. Furthermore, this study suggests that an accurate representation of large-scale atmospheric circulations in upstream regions is a key factor in seasonal forecast models for improving the predictability of extreme weather events, such as the 2018 KJ heatwave.

1. Introduction
2. Data and GloSea6 experiments
3. Results and Discussion
    Clustering patterns associated with the 2018KJ heatwave
    GloSea6 performance and clustering patterns
4. Conclusion
Acknowledgment
References

• Jinhee Kang(Division of Science Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54896, Korea)
• Semin Yun(Division of Science Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54896, Korea)
• Jieun Wie(Division of Science Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54896, Korea)
• Sang-Min Lee(Climate Research Department, National Institute of Meteorological Sciences, Seogwipo 63568, Korea)
• Johan Lee(Climate Research Department, National Institute of Meteorological Sciences, Seogwipo 63568, Korea)
• Baek-Jo Kim(Observation Research Department, National Institute of Meteorological Sciences, Seogwipo 63568, Korea)
• Byung-Kwon Moon(Division of Science Education and Institute of Fusion Science, Jeonbuk National University, Jeonju 54896, Korea) Corresponding author