Water levels are subject to 3 weather conditions:
- Atmospheric pressure
- The wind
- The waves
Atmospheric pressure
Atmospheric pressure exerts pressure on the sea surface. When you're under a high-pressure system, the sea is lower. In the case of a depression, the sea is higher. There's a table showing the correspondence between pressure in hectopascals and the tidal correction in meters. This variation can be considerable, up to 50 cm.
| Barometric pressure | Correction |
| In hectopascals | in meters |
| 963 | + 0,5 |
| 973 | + 0,4 |
| 983 | + 0,3 |
| 993 | + 0,2 |
| 1003 | + 0,1 |
| 1013 | 1023 |
| - 0,1 | 1033 |
| - 0,2 | The wind |
Depending on its direction and strength, wind can also influence water levels. If, for example, it enters a bay with a gently rising sea floor, the water level at the bottom of the bay will rise.
The waves
Large waves or swells can cause water levels to rise higher than predicted by the tide. This is often the fear of coastal dwellers when a high tide is combined with a strong storm.
