The tide desk · NOAA CO-OPS, read live
High water, low water,
and where the sea is now.
Pick a tide station and this desk reads it: the next high and the next low with a running countdown, today’s full table of highs and lows, and the day’s predicted curve drawn against the water level the station’s own gauge has actually recorded. The source is NOAA’s Center for Operational Oceanographic Products and Services — CO-OPS — read directly by this page.
There is no key, no account and no server in the middle: CO-OPS serves its API to browsers, so the page asks it the same questions you could ask it yourself. Every height is measured in feet above mean lower-low water, every time is the station’s own local time, and where a station publishes nothing the desk says so rather than filling the gap.
NOAA CO-OPS · predictions and observations · heights above MLLW · the curve drawn by this page’s own hand
The station
Every gauge NOAA predicts.
NOAA publishes tide predictions for several thousand stations, from harbour gauges that report every six minutes to small subordinate points whose predictions are offset from a nearby reference gauge. Search the list by name, by state or by station id; the list itself is read from NOAA on the first keystroke and kept in memory for the rest of the visit. The station you last looked at is remembered in this browser and nowhere else.
The station
waiting for the feed
Type to search. Arrow keys move through the matches, Enter takes one, Escape closes the list.
This station
Next water
The next turn of the tide.
Times here are the station’s own local time, which is what the
API returns when it is asked with time_zone=lst_ldt —
local standard or local daylight, whichever the station is keeping
today. That is the correct clock for a tide: a gauge in Honolulu and
a gauge in Boston both read noon at their own noon. The countdown is
measured against the offset from UTC this page works out from the
feed itself, rather than assumed from your machine’s time zone.
Next water
Today’s highs and lows
The curve
The model, and the sea.
One line is the prediction: NOAA’s six-minute astronomical forecast for the station’s own day, drawn as one curve, with the count of heights actually read printed under the plot. Over it, where the station carries a gauge, is what the water has really done — the observed water level, reported every six minutes and stopping at the last reading. The gap between the two lines is weather, and it is the most useful thing on this page.
The curve
The range
How far the water moves.
The range is the day’s highest high less its lowest low. It is about a foot at some Gulf of Mexico stations and many times that at the head of Cook Inlet in Alaska; the figures below are this station’s own, for today. Beside them, where the gauge exists, is how far the water has actually travelled since midnight.
The range
Every height on this page is given above MLLW, mean lower-low water: the average of the lower of the two daily low waters, taken over a nineteen-year tidal epoch. It is a datum, which is to say a surveyor’s agreed zero, and not the sea floor. A predicted low of 1.0 ft does not mean one foot of water; it means the water is expected to stand one foot above that agreed zero, and how much sea is under a hull at that moment is a question for a chart, whose soundings are quoted from the same datum. A negative low is ordinary rather than alarming: MLLW is an average, and a prediction below it simply means the water is expected to fall below that average.
About
A prediction is not a forecast.
The data is NOAA CO-OPS: the tide prediction service and the water level gauges at tidesandcurrents.noaa.gov, read by this page over the agency’s public API without a key. Predictions come from the harmonic constants NOAA has fitted to a reference station’s record — applied directly there, and as time and height offsets at a subordinate station. Observations come from the station’s own gauge and arrive marked preliminary until the agency has verified them. Where a station has a thermometer or an anemometer the latest reading is shown beside its name, and where it has none, nothing is shown.
The predictions on this page are astronomical. They are the sea answering the moon and the sun, and they know nothing whatever about the weather. A hard onshore wind, a deep low crossing the coast, a river in flood — any of these will put the water somewhere the prediction did not say, and a storm surge is precisely the case where the numbers here are wrong and should not be relied on. That is why the observed line is drawn over the predicted one: the gap between them is the part the model does not contain. For a warning, for a forecast, or for anything a vessel depends on, go to NOAA itself at tidesandcurrents.noaa.gov, which is the authority on every figure this desk shows.
This desk is not for navigation. It carries no chart, no soundings and no current predictions, and a subordinate station’s times are offsets applied to a reference gauge some distance away rather than measurements taken where you are standing. Nothing on the page is cached, seeded or stored: every figure is fetched when you load the page, the observed line is re-read every six minutes while you watch, and the only thing kept in this browser is which station you last chose.