Many believe that Tides are as accurate as a sunrise, but they do change.

Tide forecasts (like weather forecasts) need to be calibrated via live readings, and many of the remote locations don't have observation equipment available.

The actual water level height and speed of change may vary under certain weather conditions, such as unusually high or low barometric pressure or by prolonged strong winds.

Low-pressure systems usually raise sea levels and high-pressure systems tend to lower them. It takes some time for the water level to adjust to the pressure change, and that pressure change needs to occur over a significant area.

As you can imagine, a strong wind will raise the water level in the direction it is blowing, and may cause the "high tide" to be higher than predicted.