Convection (CAPE) — how to read it

The convection map shows Convective Available Potential Energy (CAPE) in J/kg — the thermodynamic fuel for thunderstorms. It answers "is the atmosphere ready to make storms if triggered?".

How to read J/kg

• Below 100 J/kg: stable atmosphere. Isolated showers at most, no organised convection.
• 100 to 500 J/kg: isolated summer showers possible; expect the odd Cu build-up but no thunderstorms.
• 500 to 1,000 J/kg: ordinary summer thunderstorms. Airmass storms, usually pop-up, decaying by evening.
• 1,000 to 2,000 J/kg: strong storms. Hail risk, gusty outflows. Route around, not through.
• Above 2,000 J/kg: severe / supercell environment. Rare in Central Europe but real; plan for a ground day.

The trap: CAPE alone doesn't fire storms

For the timing question ("when today do the storms fire?"), open the meteogram at your airfield and look at the CAPE/CIN panel: it shows both curves hour by hour. A day where CAPE rises past 1,500 J/kg while CIN drops below 50 J/kg is a day storms are almost certain to fire. See the meteogram guide.

Combining products for a convective day

1. Morning: check the CAPE forecast for the afternoon — is fuel expected?
2. Around midday: check simulated radar for the expected firing time and cell distribution.
3. Along the route: a cross-section tells you the vertical depth of the cells and whether you can top or under-fly them (usually you cannot).
4. Close to flight time: switch to live radar and satellite.