ONE QUESTION, WITH AN EXAMPLE
Was the water as high as the tide prediction said?
A tide prediction estimates the rise and fall of the water caused mainly by the moon and sun. A water-level station measures the actual height. At Grand Isle in 2025, the gap between those two numbers changed through the year.
Read the upper chart to compare monthly average predicted and measured heights. The lower chart subtracts the prediction from the measurement: above zero means measured water was higher, below zero means it was lower. Both use the same reference level, the zero from which heights are measured.
Positive and negative gaps can cancel in an average. In a made-up pair, a one-foot gap above and a one-foot gap below give a signed average of zero, even though neither prediction matched. The linked analysis also explains absolute differences, which count the size of each gap without its sign.
This is a comparison of height at one station in one year. It does not supply bottom depth, nearby current speed or an adjustment to today’s tide prediction.
Read the explanation and results →