Guide

Reading a tide table in Louisiana

Checked September 28, 2026 against NOAA Tides and Currents and NOAA’s National Ocean Service.

The Tides tile repeats NOAA’s predictions for the station nearest your town and, where there is one, what its gauge is measuring now. On this coast the tide is small, and the wind and the rivers can move the water more than the Moon does. This page explains what the zero is, the shape of the tide here, which station each town reads, which tables are worked out from another station, and how to read the gap between the prediction and the water.

Zero is not the bottom

Every height on the tile 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.” Because it is an average, many low tides fall below it: a prediction of −0.3 ft is not an error. A charted depth is also measured from MLLW, so a channel charted at 4 feet has less than that on a minus tide.

A small tide, often once a day

NOAA’s National Ocean Service: “Some areas, such as the Gulf of Mexico, have only one high and one low tide each day.” That is a diurnal tide, which NOAA’s glossary describes as the tide “when only one high water and one low water occur during a tidal day.” It is not the same everywhere on this coast. In NOAA’s own tables for September 2026, Grand Isle had one high tide on 24 days and the New Canal on Lake Pontchartrain on 28, while Calcasieu Pass, at the other end of the state, had two highs on 22 days. So most days the table shows one high and one low, and on some days, or at some stations, two of each. Neither is a mistake.

The range is small. NOAA’s figure for each station is the great diurnal range, “the difference in height between mean higher high water and mean lower low water.” At every station the boards read it is under two feet but one: Freshwater Canal Locks, at 2.09 feet. At Lafitte, on the Barataria Waterway, it is about a third of a foot. Pointe au Chien, on the Cut Off Canal, gets 0.44 feet and the New Canal on Lake Pontchartrain 0.54.

Which station each town reads

“Live gauge” means NOAA publishes the gauge’s measured level as it comes in; “prediction” means a table and nothing measured. The range is NOAA’s great diurnal range for that station; a dash means NOAA publishes no datum figure for it.

Southwest Louisiana, Holly Beach to Morgan City: nine stations

Bayou Coast, Houma to Grand Isle: six stations

Southeast Louisiana, Venice to the North Shore: eight stations

A town reads the nearest station NOAA publishes a table for, and the nearest is not always close: Houma reads Pointe au Chien on the Cut Off Canal, about twenty miles away, and Delcambre reads Weeks Bay, about twelve. Each tile says how far.

NOAA also has a station at Carrollton (8761955), in New Orleans, which its catalogue lists as not tidal; it publishes no tide prediction for it, and the board does not read it for the tide.

Some tables are worked out from another station

NOAA publishes two kinds of tide prediction. “Harmonic stations are stations with tidal harmonic constants and tidal datums. Tide predictions for harmonic stations are generated directly from the harmonic constants.” But “subordinate stations are historic stations which do not have tidal harmonic constants available”, and for them NOAA first makes “high/low tide predictions for a designated harmonic station, called the ‘reference station’; then time and height adjustments are applied to correct the high/low predictions to the tidal conditions at the subordinate station.”

Four of the tables on this coast are made that way, all on the Southeast Louisiana board. NOAA’s own adjustments:

• Jack Bay (Venice) is worked from South Pass (8760551): high tide 3 hours 12 minutes after South Pass’s, at the same height.
• Paris Road Bridge on the Intracoastal Waterway (Chalmette) is worked from Grand Isle (8761724): high tide 5 hours 53 minutes after Grand Isle’s, at 1.04 times the height.
• Bayou Bonfouca (Slidell) is worked from South Pass: high tide 11 hours 12 minutes later, at 0.43 times the height.
• Tchefuncta River (Mandeville and Madisonville) is worked from South Pass: high tide 11 hours 36 minutes later, at 0.48 times the height.

The low tides carry their own, slightly different, time adjustments. NOAA adds that “subordinate stations only allow for the generation of high/low tide predictions, and heights will be relative to Mean Lower Low Water (MLLW)”. So on the North Shore the table is another station’s tide, shifted by about half a day and cut to half its height, and nothing at any of the four is measured.

One gauge’s zero is provisional

NOAA marks the datums at Port Fourchon, Belle Pass as provisional: they “are provisional and subject to revision until they have been thoroughly reviewed and received final approval,” and “data users are cautioned to consider the conditional nature of this information before using it for critical decisions such as those that concern physical or public safety.” The gauge’s level is measured; the MLLW it is counted from may still move.

Why the water is not where the prediction said

NOAA is direct about what a tide table leaves out:

On a coast with a one-foot tide, those effects can be bigger than the tide. The National Ocean Service: “Onshore winds may act to pile up water onto the shoreline, virtually eliminating low tide exposures”, and “strong offshore winds can move water away from coastlines, exaggerating low tide exposures.” This coast faces the Gulf to the south, so a steady south or southeast wind is onshore and holds the water up, and the north wind behind a front is offshore and pulls it down.

River water does it too. Of tidal rivers, the National Ocean Service says “powerful seasonal river flows in the spring can severely alter or mask the incoming tide.” Berwick’s gauge is on the Atchafalaya River, and its tide is about half a foot.

How big: between October 1, 2025 and September 27, 2026, NOAA’s hourly heights ran well away from the prediction. At Shell Beach, on Lake Borgne, the water ran nearly 4 feet above it, against a daily range of 1.5. At the New Canal it ran 2.4 feet above, against a range of about half a foot. At Berwick it ran 1.8 feet above and 2.9 below, and at Calcasieu Pass 2.1 above and 2.4 below. Even at Grand Isle, on the open Gulf, it ran 1.3 feet above and 1.1 below, more than the whole daily range.

So read the tile this way. Where the station has a live gauge, the measured level is the answer and the prediction is a guide to when it will rise and fall. Where it has predictions only, treat the table as the start of the question and look at the wind forecast. And a hurricane’s storm surge is a different thing altogether; it is the weather service’s warnings, not the tide table, that speak to it.

Sources

• NOAA Tides and Currents, tidal datums — MLLW and the great diurnal range
• NOAA Tides and Currents, glossary — the diurnal tide; chart datum is lower low water in U.S. waters
• NOAA National Ocean Service, types and causes of tidal cycles — the Gulf’s diurnal tide
• NOAA National Ocean Service, what affects tides in addition to the Sun and Moon — onshore and offshore wind, river flow
• NOAA Tides and Currents, frequently asked questions — what a prediction can and cannot include
• NOAA Tide Predictions, help — harmonic and subordinate stations
• NOAA’s adjustments for the subordinate stations: Jack Bay, Paris Road Bridge, Bayou Bonfouca, Tchefuncta River; and their reference stations, South Pass and Grand Isle
• Measured water levels, every live gauge the boards read: Calcasieu Pass, Lake Charles, Freshwater Canal Locks, Berwick, Atchafalaya River, Port Fourchon, Belle Pass, Grand Isle, Shell Beach, New Canal, Lake Pontchartrain
• NOAA datums, Port Fourchon, Belle Pass — the provisional datum
• NOAA station catalogue, Carrollton — listed as not tidal