Data-driven seasonal weather forecast: An application to the Indian summer monsoon rain

I present a data-driven forecast system applied to the Indian summer monsoon rain. By forecasting pentads, 5-day rain totals, the system is well suited to forecasting the monsoon onset/withdrawal as well as its progression, also known as intra-seasonal variability. I will provide a comparison of the forecast skill with those of other systems, both physics-based NWP and AI systems. The skill of the JJA seasonal forecast issued on 1 May in terms of the Pearson correlation coefficient far surpasses that of GLOSEA5. I will also discuss delicate questions about forecast skill, as to what is concepotually sound and what can be computed.