Workshop: twelve typical days

The essentials in two minutes

1. Twelve archetypes cover the essentials: three stable (anticyclone, low inversion, pure breeze), one ideal (classic thermal), four unstable (overdevelopment, air-mass thunderstorm, slack pressure, cut-off low), four driven by the wind or the fronts (warm front, cold front and post-frontal air, foehn, bise).
2. The chart says who is in charge, the sounding what the heated air will do, the growth of the cumulus at what time.
3. Same cumulus base, opposite days: it is the humidity and the lid aloft that make the difference between well-behaved cumulus and overdevelopment.
4. Heat thunderstorms come in the afternoon (14:00–17:00); cut-off-low ones from late morning; slack-pressure ones, isolated and late.
5. Anticyclone does not mean calm: the bise and the foehn depend on the pressure gradient, not on the pressure value.
6. A cloudless day can be windy (valley breeze, bise) or give little lift (subsidence): blue on its own says nothing.
7. Every day has its pitfall: the too-beautiful morning of overdevelopment, the blue between two showers in post-frontal air, the deceptive calm under the foehn rotor, landing in the breeze.
8. The days follow one another: overdevelopment, front, post-frontal air, then a fine post-frontal day.