A short glossary of the terms used across the forecast pages, and how to read them.
| Term | Meaning |
|---|---|
| Water Level (mPWD) | River stage in metres above Public Works Datum, the national levelling reference. |
| Danger Level (DL) | The stage at which water begins to cause flooding at a station; the primary warning threshold. |
| Hindcast | Modelled/observed water level up to the present — the run-up before the forecast. |
| Forecast | Predicted water level for the coming days (typically up to a 5-day lead time). |
| Recorded Highest | The maximum stage ever observed at the station, shown for context. |
| Flash Flood | Rapid-onset flooding in the north-east, driven by intense rainfall over the bordering hills. |
| Isohyet | A contour line joining points of equal rainfall depth. |
| WRF | Weather Research & Forecasting model — the numerical weather model behind the rainfall forecast. |
| Inundation Depth | Modelled depth of standing flood water over the land surface, in metres. |
Observed and satellite rainfall feed a numerical weather forecast (WRF). The resulting rainfall drives hydrological rainfall–runoff models, whose flows are routed through a hydrodynamic model of the river network to produce water-level forecasts at each gauge station. These are compared against danger levels to assign the flood status you see on the map.