Why WSA-Enlil can miss the arrival time: how to read the data without being misled
A propagation model starts from estimates of CME speed, direction and geometry. Projection errors, interaction with background solar wind or other CMEs can make the true arrival earlier or later.
What it really means
Even the best data have limits: calibration, telemetry, time resolution, viewing geometry and propagation introduce uncertainty. Reading the original source helps explain why two apparently similar plots may not match perfectly. A very precise-looking number should not hide uncertainty. Resolution, filtering, algorithms and delays can make two valid products differ without either being wrong.
Why it matters
A scientific instrument does not automatically produce a forecast: it produces a measurement, image or model that must be interpreted. Why WSA-Enlil can miss the arrival time becomes genuinely useful only when we know what it measures, where the data are acquired and how much delay is involved. Before using it to decide whether to go outside, determine whether you are looking at an observation, a derived product or a forecast. It is a simple distinction, but it radically changes what the plot means.
How to interpret it without oversimplifying
For Aurora Hunter, separating observation from modelling is essential. A sensor can describe what is happening now; a model combines measurements and assumptions to estimate what may happen next. Confusing the two creates false certainty.