Nowcast
Models & data Very short-range forecast Short-term forecast Nowcasting
A nowcast predicts the next few minutes to a few hours. It relies especially closely on recent observations.
What the rain is doing right now
A nowcast uses data such as radar, satellite images and station observations. A simple method tracks a rain area through several images and projects its movement forwards. More advanced methods account for development or combine observations with weather models.
When it is especially useful
If an existing rain band moves steadily, its arrival in the next area can often be estimated reasonably well. For a short bike ride, this is usually more useful than a rain symbol covering the whole day.
Why the result can suddenly miss
- A new shower forms where the radar was clear.
- A cell grows rapidly or fades.
- Wind and direction of movement change.
Simple extrapolation has limited ability to represent such changes. It moves existing rain but cannot reliably invent the next shower.
Check the timestamp and the transition
Our radar display shows observations followed by a short forecast. That transition matters: an image of the future has not been measured. The farther ahead it lies, the less certain its exact position becomes. Tomorrow’s weather requires a longer-range model forecast.