Lassoing Fish — Linking tropical Fish cloud structures to extratropical fronts

People on Barbados are used to “rope-like” cloud structures passing over the island and their association with more disturbed weather conditions. In more recent literature, such cloud structures are frequently named Fish owing to their fishbone-like appearance on satellite images. Schulz et al., 2021, identified Fish cloud structures in satellite imagery via machine learning and showed that they have a pathway coming from the extratropics and often show a frontal character based on their surface convergence field, both indicative of them being associated with extratropical fronts. Extratropical fronts are known to impact convection in the tropics. A wealth of past studies based on theory, observations and modelling showed the distinct water-vapor structure, precipitation characteristics, as well as radiative-dynamical mechanisms of extratropical intrusions and highlight their importance for tropical moist convection.

In our study, we investigate the link between well-studied extratropical fronts and Fish-like cloud appearances. We apply a neural network to identify Fish cloud structures across the global tropics and investigate them with respect to the characteristics of well-studied extratropical fronts. We aim to answer the questions whether all Fish patterns are the visual imprint of extratropical fronts and how their thermodynamical and dynamical properties change as they propagate to lower latitudes.