SINGV‐DA is a convective‐scale numerical weather prediction system with regional data assimilation for Singapore and the surrounding region. This article documents SINGV‐DA's current operational configuration and the sensitivity studies that influenced its development. We show that background error covariances derived by bootstrapping (via the lagged National Meteorological Centre method) contain spurious vertical structures at higher model levels that may degrade forecast performance. We found that SINGV‐DA precipitation forecasts are sensitive to horizontal resolution and lateral boundary conditions. Our observing system experiments reveal that satellite radiance assimilation, while clearly beneficial for precipitation forecasts in this region, adversely affected model background temperatures and winds at higher altitudes. Benchmarked against the forecast model in isolation, the regional DA system adds significant value to precipitation forecasts in the nowcasting range, but not at longer lead times. Our findings point to the need for further research and development to improve the system.

This article describes the development and ocean forecast evaluation of an atmosphere–ocean coupled prediction system for the Maritime Continent (MC) domain, which includes the eastern Indian and western Pacific oceans. The coupled system comprises regional configurations of the atmospheric model MetUM and ocean model NEMO at a uniform horizontal resolution of 4.5 km × 4.5 km, coupled using the OASIS3-MCT libraries. The coupled model is run as a pre-operational forecast system from 1 to 31 October 2019. Hindcast simulations performed for the period 1 January 2014 to 30 September 2019, using the stand-alone ocean configuration, provided the initial condition to the coupled ocean model. This paper details the evaluations of ocean-only model hindcast and 6 d coupled ocean forecast simulations. Direct comparison of sea surface temperature (SST) and sea surface height (SSH) with analysis, as well as in situ observations, is performed for the ocean-only hindcast evaluation. For the evaluation of coupled ocean model, comparisons of ocean forecast for different forecast lead times with SST analysis and in situ observations of SSH, temperature, and salinity have been performed. Overall, the model forecast deviation of SST, SSH, and subsurface temperature and salinity fields relative to observation is within acceptable error limits of operational forecast models. Typical runtimes of the daily forecast simulations are found to be suitable for the operational forecast applications.

This article describes the development and ocean forecast evaluation of an atmosphere-ocean coupled prediction system for the Maritime Continent (MC) domain, which includes the eastern Indian and western Pacific Oceans. The coupled system comprises regional configurations of the atmospheric model MetUM and ocean model NEMO, at a uniform horizontal resolution of 4.5 km × 4.5 km, coupled using the OASIS3-MCT libraries. The coupled model is run as a pre-operational forecast system from 1 to 31 October 2019. Hindcast simulations performed for the period 1 January 2014 to 30 September 2019, using the stand-alone ocean configuration, provided the initial condition to the coupled ocean model. This paper details the evaluations of ocean-only model hindcast and 6-day coupled ocean forecast simulations. Direct comparison of sea surface temperature (SST) and sea surface height (SSH) with analysis as well as in situ observations are performed for the ocean-only hindcast evaluation. For the evaluation of coupled ocean model, comparisons of ocean forecast for different forecast lead times with SST analysis, and in situ observations of SSH, temperature and salinity have been performed. Overall, the model forecast deviation of SST, SSH, and subsurface temperature and salinity fields relative to observation is within acceptable error limits of operational forecast models. Typical runtimes of the daily forecast simulations are found to be suitable for the operational forecast applications.

The Maritime Continent (MC), located between the Pacific and Indian Oceans, is a critical region for global weather and climate systems due to its complex geography, intense precipitation, and vital role of air-sea interactions. Accurate modeling of coupled ocean-atmosphere dynamics in this region can potentially improve weather forecasts and climate projections. This study presents the development and evaluation of a fully coupled operational forecast model, integrating the UK Met Office atmospheric model (Unified Model v11.1) with the Nucleus of European Modelling of the Ocean (NEMO v3.6), at a horizontal resolution of 4.5 km, specifically tailored for the MC. The coupled model is designed to enhance atmospheric forecast accuracy by capturing air-sea interactions. Model performance was assessed using observational datasets and reanalysis products, focusing on precipitation, wind speed, and air temperature. Results show an improved forecast accuracy for the coupled model over a standalone atmospheric model. A case study on Typhoon Nakri further demonstrates an improved 10 m wind speed simulations with the coupled model, aligning more closely with reanalysis data. Air temperature forecasts, especially during nighttime and at longer lead times, also benefited from ocean-atmosphere coupling, with verification against meteorological stations confirming improved accuracy in regions with strong oceanic influence.

This paper presents a new blending approach to applying large-scale correction to the initial condition in a limited-area numerical weather prediction (NWP) model. The new approach combines the implementation benefits of the known approaches and shows significant improvement in the forecast quality when implemented in a tropical NWP model. Sensitivity studies indicate that many improvements come from blending the horizontal winds alone. Adding temperature and specific humidity to the horizontal winds result in forecast quality degradation in the early hours of the simulated tropical environment.