CoastCoastCue field guide
Why your tide app and the water can disagree
A tide app can display a correct NOAA prediction while the water in front of you looks different. The fastest diagnosis is to verify the label and location first, then separate astronomical prediction from live conditions.
Verify station, datum, and local time
Confirm that the station sits on the same connected water body, that heights use the expected datum such as MLLW, and that times use the station's local clock. A nearby station across a barrier island or farther inside an estuary may turn at a different time.
Check whether the value is predicted or observed
Predicted values come from NOAA tide math. Observed values come from a physical water-level sensor and include weather-driven effects. An Estimated value may apply a clearly labeled short-lived correction while retaining the original NOAA prediction for comparison.
Account for wind, pressure, rain, and rivers
Sustained wind can pile water against a coast or push it away. Atmospheric pressure, runoff, river discharge, and storms can also move observed levels above or below the tide table. These effects vary by location and can persist across more than one tide turn.
Check age, cache, and partial outages
An offline or saved forecast should show its age rather than masquerade as current. One NOAA or NWS product may also fail while other data remains usable. Refresh when connected, read the timestamp, and do not treat a stale or partial value as a live measurement.