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(Information provided by the National Oceanographic and Atmospheric Administration on the NOAA web site.)
How Accurate are Tide Prediction Charts?
The accuracy of the tide predictions is different for each location.
Periodically NOAA does a comparison of the predicted tides versus the observed tides for a calendar year. The information generated is compiled in a Tide Prediction Accuracy Table. NOAA works to insure that the predictions are as accurate as possible. However, NOAA can only predict the astronomical tides; they cannot predict the effect that wind, rain, freshwater runoff, and other short-term meteorological events will have on the tides.
In general, predictions for stations along the outer coast are more accurate than those for stations farther inland; along a river, or in a bay or other estuary. Inland stations tend to have a stronger
non-tidal influence; that is, they are more susceptible to the effects of wind and other meteorological effects than stations along the outer coast. An example of an inland station which is
difficult to predict is Baltimore, Maryland. This station is located at the northern end of Chesapeake Bay. Winds which blow along the length of the bay have been known to cause water levels to be 1-2
feet above or below the predicted tides.
Stations in relatively shallow water, or with a small tidal range, are also highly susceptible to meteorological effects and thus difficult to accurately predict. At these stations, short-term
weather events can completely mask the astronomical tides. Many of the stations along the western Gulf of Mexico fall into this category. An example is Galveston, Texas. This station is in a
bay which is relatively shallow and has a small opening to the sea. At this station it is possible for meteorological events to delay or accelerate the arrival of the predicted tides by an hour or more.
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