The spatiotemporal evolutions of equatorial Atlantic sea surface temperature anomalies (SSTAs) during Atlantic Niño events and the associated climate impacts on the surrounding continents are extremely diverse. In this study, we construct longitude-time maps of equatorial Atlantic SSTAs for each observed Atlantic Niño event during 1948-2019 and perform a spatiotemporal empirical orthogonal function analysis to identify the four most frequently recurring Atlantic Niño varieties. The first two contrast the timing of dissipation (early terminating vs. persistent) and the other two the timing of onset (early onset vs. late onset). Largely consistent with the differences in the timings of onset and dissipation, these four varieties display remarkable differences in rainfall response over West Africa and South America. Most of the varieties are subject to onset mechanisms that involve preconditioning in boreal spring by either the Atlantic meridional mode or Pacific El Niño, while for the late onset variability there is no clear source of external forcing.Plain Language Summary A phenomenon known as Atlantic Niño is characterized by the appearance of warm sea surface temperature anomalies (SSTAs) in the eastern equatorial Atlantic in northern summer. When it attains its full strength, it increases rainfall and the frequency of extreme flooding over the West African countries bordering the Gulf of Guinea and in northeastern South America. Atlantic Niño thus has a direct socioeconomic impact in emerging countries in these regions. However, not all Atlantic Niño events are alike. Some appear earlier than others or persists longer. These variabilities during the onset and dissipation phases are well captured by the four most recurring Atlantic Niño varieties identified in this study. Largely consistent with the differences in the timings of onset and dissipation, these four varieties display remarkable differences in rainfall response over West Africa and South America. Most of the varieties are subject to preconditioning in northern spring by cold SSTAs in the North Atlantic or El Niño in the Pacific, except for one variety with no clear source of external forcing.

An ocean circulation forecasting model for the Madeira Archipelago is operational since May 2010. Developing a forecasting system for a small island oceanic region, deprived from in-situ observations, is a challenging task since there are limited ways to validate predictions. Furthermore, model resolution concurrent with insufficient computational power, locally available, are other limiting factors to consider. Regional models combined with the possibility to downscale solutions onto a higher resolution island-scale model is a way to overcome some of such limitations. Nevertheless, generalised regional models must be able to accurately represent the far-field and transport important features such as meddies onto the local systems; while island-scale models must have sufficient grid resolution as well as adequate physics and accurate atmospheric forcing to resolve the near-field phenomena. An island-induced cyclonic eddy event was successfully observed and forecasted with the current approach (regional-local). Generalised single (regional) model initiatives will prove to be insufficient to deal with mesoscale dynamic systems, islands and seamounts are important generators of mesoscale features in the NE Atlantic, with basin scale implications. The forecasting systems of the future should also consider upscaling valid local (island-scale) solutions onto Regional and/or Global models.

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