Influence of Winter Pressure Patterns on Regional Weather Forecast Accuracy
Maya Takemoto
Fujimigaoka High School for Girls, Tokyo, Japan
Publication date: November 20, 2025
Fujimigaoka High School for Girls, Tokyo, Japan
Publication date: November 20, 2025
DOI: http://doi.org/10.34614/JIYRC2025II25
ABSTRACT
This study analyzed winter forecast accuracy for 17 Japanese cities from 2020 to 2025, examining two synoptic pressure patterns: West High-East Low (WHEL) and South Coast Low (SCL). The SCL pattern initially showed lower relative MSE for temperature forecasts, but this advantage gradually diminished over time. From 2024 onward, the SCL pattern also exhibited lower F1 scores for precipitation forecasts. These findings suggest increased forecast difficulty under SCL conditions. Pacific coastal cities showed higher temperature forecast MSE compared to inland and the Sea of Japan coastal cities. However, large prediction errors were not consistently associated with the SCL pattern, indicating that forecast accuracy depends on both pressure patterns and region-specific factors such as coastal topography and mesoscale interactions. Future research should examine the influence of long-term climate factors and refine classification methods, and these findings enable more effective regional risk assessment and disaster preparedness strategies.
This study analyzed winter forecast accuracy for 17 Japanese cities from 2020 to 2025, examining two synoptic pressure patterns: West High-East Low (WHEL) and South Coast Low (SCL). The SCL pattern initially showed lower relative MSE for temperature forecasts, but this advantage gradually diminished over time. From 2024 onward, the SCL pattern also exhibited lower F1 scores for precipitation forecasts. These findings suggest increased forecast difficulty under SCL conditions. Pacific coastal cities showed higher temperature forecast MSE compared to inland and the Sea of Japan coastal cities. However, large prediction errors were not consistently associated with the SCL pattern, indicating that forecast accuracy depends on both pressure patterns and region-specific factors such as coastal topography and mesoscale interactions. Future research should examine the influence of long-term climate factors and refine classification methods, and these findings enable more effective regional risk assessment and disaster preparedness strategies.
