Guide
Reading a tide table on this coast
Checked September 13, 2026 against NOAA Tides and Currents.
The Tides tile repeats NOAA’s predictions for the station nearest the town you are reading for. This page explains what the zero on that scale is, which stations on this coast are real instruments and which are arithmetic, and why the water is not always where the prediction says.
Zero is not the sea bed
Every tide height on this coast is measured from mean lower low water — MLLW — which NOAA defines as “the average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch.” In plainer terms: of the two low tides most days bring, take the lower one, and average it over about nineteen years. That average is zero.
Because it is an average, roughly half of all lower low tides fall below it. A prediction of −1.5 ft is not an error; it is a tide a foot and a half lower than the long-run average low, and those are the tides a clam digger wants and a boat crossing a bar does not.
It also means a charted depth of 6 feet is 6 feet at MLLW. On a minus tide there is less water over it than the chart says.
Some stations measure. Some only calculate.
NOAA distinguishes stations that carry tidal harmonic constants from stations that do not. A harmonic station has the constants, and predictions “are generated directly from the harmonic constants.” A subordinate station has none, so its high and low tides are produced by predicting them at another station and then applying time and height corrections.
That is a distinction about arithmetic, and it is worth saying plainly that it is not the same as whether there is an instrument in the water. This board reads nine stations, and only two of them have a gauge in the water: Toke Point and Cape Disappointment. The other seven are predictions, and a prediction cannot tell you the water is already over the road.
| Station | Water level now? | Also reports |
|---|---|---|
| Neah Bay 9443090 | Yes | water temperature, pressure. No wind, no air temperature. |
| La Push 9442396 | Yes | wind, air temperature, water temperature, pressure |
| Westport 9441102 | Yes | wind, air temperature, water temperature, pressure |
| Toke Point 9440910 | Yes | wind, air temperature, water temperature, pressure |
| Cape Disappointment 9440581 | Yes | nothing else — water level only |
| Aberdeen 9441187 | No | predictions only; the gauge was removed in 2005 |
| South Bend 9440875 | No | predictions only; the gauge was in place for two months in 1982 |
Five of the seven can tell you what the water is actually doing right now. Aberdeen and South Bend can only tell you what it was expected to do — and the expectation has had no instrument checking it for twenty years in one case and forty in the other. That is not a reason to distrust the prediction; it is a reason to know which kind of number you are looking at.
Three stations — La Push, Westport and Toke Point — report wind. That is often the fastest honest answer to “what is it doing out there” on a coast where weather stations are thin.
Why the water is not where the prediction said
NOAA is direct about the limits of what a tide table is:
“We can only predict the astronomical tides; water level changes created by the gravity of the Moon, and the relative motions of the Earth, Sun and Moon.”
“We cannot predict the effect that wind, rain, freshwater runoff, and other short-term meteorological events will have on the tides.”
On this coast all four of those are routine. A hard southwesterly piles water against the shore and holds a low tide higher than predicted. Low barometric pressure lets the sea stand higher. Winter rain down the Chehalis, the Willapa or the Columbia raises the level in the estuaries and can hold the ebb back. The published time of low water can arrive late, or the low can simply never get as low as the table says.
This matters most to the two activities this coast does on a minus tide: crossing a bar, and digging clams in the dark. If the tide is running an hour behind and a foot high, both of those plans were made on a number that is no longer true. Where a station has a live gauge, the observed level is the answer; where it does not, assume the prediction is the beginning of the question.
What NOAA says about relying on it
NOAA’s own disclaimer is worth reading once: real-time data “have not been subjected to the National Ocean Service’s quality control or quality assurance procedures,” and “the user assumes the entire risk related to its use of these data.” Its model-based water level forecasts are “accurate to within 6 inches 90% of the time” — which is to say that one time in ten they are not.
None of that makes the tide table unreliable for planning. It makes it a prediction, which is a different thing from a measurement, and the board labels which one it is showing you and when it was taken.
Sources
- NOAA Tides and Currents, tidal datums — the definition of MLLW
- NOAA Tides and Currents, help for tide predictions — harmonic and subordinate stations in NOAA’s own words
- NOAA Tides and Currents, frequently asked questions — what a prediction can and cannot include
- NOAA Tides and Currents, disclaimers
- Station pages: Neah Bay, La Push, Westport, Toke Point, Cape Disappointment, Aberdeen, South Bend