Wind carries airborne radioactive material toward wherever it is blowing to, and rain brings it down, so a settlement keeps a wind and rain log to decide when to shelter, which ground to distrust and when a shift in wind could bring a plume its way. The log supports caution but cannot predict a plume, because the winds that carry fallout aloft can differ from the wind at ground level.
Part of Radiation Safety
Weather monitoring here means recording wind direction, wind strength and precipitation to anticipate where airborne contamination travels and settles.
Name The Wind By Where It Comes From
Wind is named for the direction it blows from, not toward (see Wind Direction Reading). A wind from the west blows material toward the east. The parent article, Nuclear Safety, says fallout follows the wind and that ignoring wind direction is a common mistake. Confusing “from” and “toward” is the way to shelter on the wrong side or flee into the plume.
What To Record
| Item | How | Why |
|---|---|---|
| Wind direction | A vane, a ribbon or smoke; see Wind Direction Reading | Which way material moves |
| Wind strength | Estimate by effects; see Wind Speed Estimation | How fast it arrives |
| Rain | Time it started and stopped | Rain brings material down |
| Date and hour | Always | The 7-10 rule needs time since the event |
Keep it as a written log; see Record Keeping. A shift in the wind (see Wind Patterns) is a signal to review which side of the settlement is exposed. For forecasting changes, see Weather Forecasting.
Worked Example: When Could It Arrive
Hypothetical: a source 50 km away, directly upwind, and a steady wind of 5 m/s. Distance 50,000 m divided by 5 m/s is 10,000 s, which is 2.8 hours. This is the earliest arrival for material carried at wind speed. Heavier particles fall out sooner and nearer, and lighter ones travel farther. So the arithmetic gives a time to prepare, not a prediction. The wind and distance in the example are invented.
The Limits Of A Ground-Level Log
Fallout is lifted to height and carried by the winds there, which can differ in direction and speed from the wind at your feet (recalled general knowledge, not from the corpus). The log shows only what blows at the settlement. The practical consequence is to act on the worst case: after any event that could produce fallout, shelter first and decide afterwards, whatever the local wind. Rain after an event is the most important item to note: it may bring material down on the spot; the parent article advises that water collected afterwards be treated as suspect, see Food & Water Safety.
Common Mistakes
- Reading the wind as “toward”.
- Trusting a clear sky. Fallout does not need clouds.
- Using the log to declare the other side of the settlement safe.
- Not writing the time. Without time since the event, the 7-10 rule is useless; see Fallout Patterns.
Safety
Do not go out to check the wind during a fallout event
The point of monitoring is to decide while sheltered. Observe from a window or a shielded point and use a vane fixed in advance. Anyone who must go outside follows Personal Protection and decontaminates afterwards.
What’s Next
- Learn next: Shelter Design — where to spend the dangerous hours
- Combine with: Weather Forecasting — reading the weather ahead