The active-break cycle of monsoons is the most important phenomenon of the Indian summer monsoon, and its prediction in real time will help to review the ongoing monsoon conditions for providing outlooks to farmers and disaster managers. The monsoon seasons of 2017 and 2018 during July–August witnessed many active-break-active transitions, with long dry spells. The recently implemented Climate Forecast System version 2 coupled model-based ensemble prediction system at the India Meteorological Department was used to observe the performance of a real-time extended-range forecast (ERF) of active-break-active cycles of the monsoon at different spatial scales during 2017 and 2018. The results indicated that the operational ERF has good fidelity in predicting the active-break-active transitions of the monsoon during 2017 and 2018 based on large-scale indices including the monsoon intraseasonal oscillation and low-level circulation. Quantitatively, the forecast of all India and central India rainfall during the active, break and transition phases of the monsoon are very well captured with a lead time of 2–3 weeks. In particular, the long dry spell during first 3 weeks of August and the active last week of August 2017 associated with very heavy rainfall over western coastal states of India were very well captured, whereas the active phase over the southern peninsula during 10–16 August 2018 was slightly underestimated. At smaller spatial scales, the ERFs for 36 meteorological (met)-subdivisions of India for 2–3 weeks could provide useful guidance to farmers during different monsoon phases. Thus, the skilful real-time ERF of the monsoon is very useful to user communities.

中文翻译：

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耦合模型集合预测的印度季风的主动中断转变

季风的活跃中断周期是印度夏季风最重要的现象，其实时预测将有助于审查正在进行的季风条件，为农民和灾害管理人员提供展望。2017 年和 2018 年 7 月至 8 月的季风季节见证了许多活跃 - 中断 - 活跃的过渡，具有长时间的干旱期。印度气象部门最近实施的气候预报系统第 2 版耦合基于模型的集合预报系统用于观察不同季风活动-中断-活动循环的实时扩展范围预报 (ERF) 的性能。 2017 年和 2018 年的空间尺度。结果表明，基于季风季内振荡和低层环流等大尺度指标，业务ERF对2017年和2018年季风活动-断-活动转换具有较好的预测性。从数量上讲，在 2-3 周的提前期，对季风活跃、中断和过渡阶段的所有印度和印度中部降雨量的预测都得到了很好的捕捉。特别是，8 月前 3 周的长旱期和 2017 年 8 月最后一周的活跃期与印度西部沿海州的强降雨相关，得到了很好的捕捉，而 8 月 10-16 日期间南部半岛的活跃期2018 年被略微低估了。在较小的空间尺度上，印度 36 个气象（气象）分区 2-3 周的 ERF 可以在不同季风阶段为农民提供有用的指导。因此，季风的熟练实时 ERF 对用户社区非常有用。