South Africa/Lesotho/Eswatini, 9 km. Experimental, real-time, ingredients-based severe-convective-environment diagnostic. Not historically trained, not a calibrated probability, not a warning service. See SAWS for official warnings.
SCEP is an experimental 0-100 scale answering one question at every point on the map: "if a thunderstorm forms here, how supportive is the surrounding atmosphere for it to become severe?" It does not say whether a storm will actually form, and it is not an estimate of the odds of one — for that, see the Simulated Radar map (which shows where the model itself develops storms) and SAWS's official warnings.
The score blends four ingredients forecasters have long used to judge storm potential:
| Ingredient | What it captures |
|---|---|
| Instability aloft | How much energy is available high in the storm, in its cold upper part, where large hail and strong updrafts form. |
| Wind shear | How much wind speed and direction change with height. A sheared environment helps storms organise and persist rather than collapsing quickly. |
| Low-level moisture | How much water vapour is available near the ground to feed a developing storm. |
| Freezing level height | Where the atmosphere crosses 0°C. Too low or too high each work against a storm reaching its most severe potential. |
A fifth factor, atmospheric "capping" (inhibition), is applied afterward to pull the score down where a stable layer would likely prevent storms from forming at all, even if the four ingredients above look favourable.
Each ingredient is scored from 0 (unfavourable) to 1 (highly favourable) against fixed, physically reasoned thresholds — not statistics fitted to past storm reports. The four scores are then combined so that no single strong ingredient can carry the result on its own; several need to line up together before SCEP reads high. SCEP_40KM (shown alongside SCEP above) reports the highest SCEP value found within about 40 km of each point — useful for spotting a nearby area of concern even where the point directly underneath reads calm.
What SCEP is not: it is not a probability, not a warning, and not calibrated against historical severe-weather reports for this region. Treat it as a same-day planning aid alongside the official SAWS warnings and radar map, not a substitute for either.