About
Sources and method
Every number here is NOAA's. This page says which feed, how it is processed, and how fresh it is.
Sources
- Tide predictions: NOAA CO-OPS tide predictions
via the CO-OPS data API (product
predictions, interval hilo, datum MLLW, feet, local standard/daylight time). Reference stations are harmonic predictions; subordinate stations are NOAA's own offset-adjusted predictions. The station list, datums and offsets come from the CO-OPS metadata API. - Water temperature (shore): CO-OPS
water_temperatureproduct, hourly, from 239 sensor stations. "Typical" temperatures are the mean of five years of hourly readings for the calendar month at that sensor. - Water temperature (buoys): NOAA National Data Buoy Center latest observations
(
latest_obs.txt), stations with a reported WTMP only. Buoys are grouped under the state of the nearest NOAA tide station, within 120 miles. - Great Lakes: NOAA GLERL GLSEA daily lake-average surface temperature (ERDDAP dataset glsea_avgtemps_3).
Cadence
Pages rebuild once a day (this build: , 09:20 UTC). Tide predictions are fetched from NOAA once a year for the current and following year; water temperatures, buoy observations and lake temperatures are fetched at each build. A station page's "now" marker and "rising toward" line update in your browser to the current time; everything else is as of the build.
Method
- The tide curve is a cosine interpolation between NOAA's consecutive high and low predictions, the standard way to draw a curve from a hi/lo table. It is a drawing aid, not a 6-minute prediction.
- Sunrise and sunset use the NOAA solar equations (zenith 90.833 degrees) at the station's coordinates, accurate to about a minute.
- Moon phase and illumination use a mean synodic month from the January 2000 new moon, within about a day of the true phase.
- A tide station's water temperature is the nearest reporting NOAA sensor or buoy within 100 miles; the page says which and how far.
- Daylight saving time follows the U.S. rule; Hawaii, Puerto Rico, the U.S. Virgin Islands, Guam, the Northern Mariana Islands and American Samoa do not observe it.
What this site does not do
It is not for navigation and gives no forecast of observed water levels: storms, wind and pressure move real water levels away from the predictions. It does not predict water temperature. It shows nothing it cannot trace to the NOAA feeds above; where a feed is missing, the section is omitted.