weather
The one question every weather consumer asks: what is the weather here,
now? weatherAt(base, cells, x, z) answers it from the scene's base weather
plus every weather CELL that reaches the point. A cell is a region that differs
(a lee behind a ridge, a storm), the climate layer of a province, and a
moving cell is a weather system. The design is in
WEATHER-DESIGN.md.
Composition is per quantity, and a province's climate (province-climate) uses the same rules for the quantities they share:
| quantity | rule | why |
|---|---|---|
wind |
vector SUM | a lee subtracts, a gust adds |
temperature |
signed SUM | opposing regions cancel |
coverage |
SUM, clamped 0–2 | a storm thickens the sky, a clear cell thins it; past 1 is THICKNESS (a storm tower), as on the deck's own dial |
precipitation |
MAX | two storms overlapping do not rain twice as hard |
storminess |
MAX | the worst one wins |
Pure and Babylon-free, so the simulation (and a driver) can ask the same question the renderer does.