El Nino Watch
The lowest level the island can be at, computed from the factors that do have data.
Koh Samui watch
`level_floor` applies the same rules as the full level (maximum of the factors, compound hazards, 'leave' rules) to the factors that are known.
Limits. The floor can hide a higher real level if the missing factor is the dangerous one (for example, no wave data during a storm).
Read 'At least Prepare (El Nino)' as: even without the missing data, you should already be at 'Prepare'. The real level may be higher, never lower. Actions and triggers shown while the level is Unknown are based on this floor.
During a strong El Nino some signals (the event itself, a cyclone report) arrive even when a local weather feed is down: the floor keeps them useful.