The transition grammar: per current type, the weighted set of plausible
next types. Implausible jumps are absent (weight 0) — clear never
jumps straight to storm; it must pass through overcast/rain
(the coherence acceptance criterion). snow is reachable only from
overcast/snow, so a snow spell only forms after clouding over.
The transition grammar: per current type, the weighted set of plausible next types. Implausible jumps are absent (weight 0) —
clearnever jumps straight tostorm; it must pass throughovercast/rain(the coherence acceptance criterion).snowis reachable only fromovercast/snow, so a snow spell only forms after clouding over.