Marine ecosystems in the Northwest Pacific (NWP) are being threatened by marine heatwaves (MHWs), which are abnormally high sea-surface temperature (SST) lasting for more than 5 days. However, there is limited research on the predictability of these MHWs. In this study, we investigate the predictability of NWP MHWs in summer using daily data from the coupled climate forecast system (version 1.0) of the Nanjing University of Information Science and Technology (NUIST-CFS1.0) for the period of 1984–2020. We demonstrate that the NUIST-CFS1.0 hindcasts can predict the spatial pattern of the total MHW days (HWD) over the NWP in summer with a lead time of up to eight months. Moreover, the linear trend and interannual variability can be predicted at lead times of up to nine and three months, respectively. We reveal that the interannual variability of HWD is strongly correlated with the preceding El Niño-Southern Oscillation (ENSO); and its predictability also shows significant interannual variability, with MHWs being more predictable in the decaying years of stronger El Niño events. In the El Niño decaying summers, there is an increase in the occurrence of MHWs; the spatial distribution of HWD can be predicted at lead times of up to 19 months, and its forecasting accuracy is far superior to that of the other years. The occurrence of MHWs during El Niño decaying summers is closely linked to strengthened NWP subtropical anticyclone (NWPSA), which increases solar radiation reaching the ocean surface and suppresses surface evaporation, leading to increased SST and thereby MHWs. The remarkable predictability of the MHWs in the NWP region during El Niño decaying summers can be attributed to the high skill at predicting ENSO and its associated NWPSA anomalies.

西北太平洋 (NWP) 的海洋生态系统正受到海洋热浪 (MHW) 的威胁，海洋热浪是指持续超过 5 天的异常高海面温度 (SST)。然而，对这些 MHW 的可预测性的研究有限。在本研究中，我们利用南京信息工程大学耦合气候预报系统（NUIST-CFS1.0）（NUIST-CFS1.0）1984-2020年期间的每日数据，研究了夏季NWP MHW的可预测性。我们证明，NUIST-CFS1.0 后报可以预测夏季 NWP 上的总 MHW 天数 (HWD) 的空间模式，提前时间长达八个月。此外，线性趋势和年际变化可以分别在长达九个月和三个月的提前期进行预测。我们发现HWD的年际变化与之前的厄尔尼诺南方涛动（ENSO）密切相关；其可预测性还显示出显着的年际变化，在厄尔尼诺事件较强的年份中，MHW 的可预测性更高。在厄尔尼诺现象减弱的夏季，MHW 的发生率有所增加；HWD的空间分布预测周期长达19个月，预测精度远优于其他年份。厄尔尼诺现象减弱的夏季期间MHW的发生与NWP副热带反气旋（NWPSA）的加强密切相关，NWPSA增加了到达海洋表面的太阳辐射并抑制了表面蒸发，导致海表温度增加，从而导致MHW增加。厄尔尼诺衰减夏季期间 NWP 地区 MHW 的卓越预测能力可归因于预测 ENSO 及其相关 NWPSA 异常的高技能。