The observations of Neptune carried out in September and November 2018 show the first evidence of a huge storm brewing, with the discovery of a new northern Great Dark Spot (visible here to the upper left of the planet’s disc, partially overlapping a large patch of white). This new dark storm is of a similar size and shape to the storm discovered in 1989 by the Voyager 2 space probe. While the future evolution of the storm will be tracked through the continued yearly Hubble observations and also by ground-based telescopes, older OPAL observations from Hubble show that its appearance was preceded by increased cloud activity throughout the region. There are hints of the storm forming in images from as early as 2015. This slow origin process indicates that the storm developed deep within Neptune’s atmosphere, pulling up dark material from its depths, and only became visible once the top of it reached higher altitudes.
