Guide

Reading a tide table on Mobile Bay and the Gulf

Checked September 29, 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 table is 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, usually 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.” In NOAA’s own tables for September 2026, the Mobile State Docks and Fly Creek had one high tide on 26 days, Dauphin Island on 25 and Alabama Point on 21. So most days the table shows one high and one low, and on some days 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 this board reads it is under two feet: 1.73 at Fly Creek, up the bay; 1.22 at Dauphin Island; 0.86 at Alabama Point, on Perdido Pass.

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. This board reads nine stations. The range is NOAA’s great diurnal range for that station; a dash means NOAA publishes no datum figure for it.

One table is 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.”

One table on this board is made that way: Mobile Point, at Fort Morgan, is worked from the Mobile State Docks (8737048), about thirty miles up the bay. NOAA’s adjustment: high tide 1 hour 46 minutes before the State Docks’, low tide 1 hour 32 minutes before, at 0.8 times the height. 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)”. Nothing at Mobile Point is measured.

Why the water is not where the prediction said

NOAA is direct about what a tide table leaves out:

On a coast with a tide of under two feet, 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.” The Mobile State Docks gauge is on the Mobile River, at the head of the bay.

How big: between October 1, 2025 and September 29, 2026, NOAA’s hourly heights ran well away from the prediction. At the Mobile State Docks the water ran 2.9 feet above it and 2.3 below, against a daily range of 1.6. At Bayou La Batre it ran 2.7 feet above and 1.9 below, and at Dauphin Island 2.1 above and 1.3 below. Each is 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
• 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 adjustment for Mobile Point, and its reference station, the Mobile State Docks
• Measured water levels, every live gauge the board reads: Dauphin Island, Bayou La Batre Bridge, Mobile State Docks
• NOAA’s datums for each station, which give the great diurnal range: for example Dauphin Island