|QUALITY CONTROLLED STATION DATA|
|Fast Delivery||Research Quality|
|HOURLY:||.dat .csv .nc||.dat .csv .nc|
|DAILY:||.dat .csv .nc||.dat .csv .nc|
This product provides a preliminary look at the recent hourly water levels observed by the tide gauge station compared to the astronomical tidal prediction. Residuals (observations minus the predictions) are indicative of the local sea level anomaly.
Data processing of high-frequency tide gauge measurements automatically removes most sensor and transmission errors, converts the data into hourly observations, and chooses the best sensor gauge for each station. Daily updates are typically available by 3:00 GMT (17:00 HST) to provide data through the previous day.
These observations have not been subjected to the UHSLC’s manual quality control procedures (Fast Delivery and Research Quality data). The Rapid Delivery data shown here is for limited public use as preliminary data to be used only with appropriate caution.
Tide predictions are calculated based on harmonic analysis of the hourly water levels measured during the Station Datum Epoch. That is, observations of the past are used to predict the future. While called predictions, the tidal calendars are extremely deterministic many years into the future. Astronomical knowledge (relative positions of the Earth-Moon-Sun) provides information about the gravitational pull on the oceans, which forces most of the tidal cycles.
We update the span of tide calendars on a yearly basis to cover the previous and future couple of years. Graphical calendars from the early months include observed water levels overlaid on the prediction, which gives a sense of how well the tide prediction performed in the past.
Tidal harmonics and the associated predicted future water levels are calculated using the Unified Tidal Analysis and Prediction “UTide” procedure. Harmonic analysis is performed over the Station Datum Epoch, which is ideally 19-years to cover a full lunar nodal cycle; however, useful tide predictions are often achieved using water level records as short as two years. Our tide predictions are based on 68 harmonic constituents, which include the annual, semi-annual, and nodal (18.6 year wobble of the Moon’s orbit around the Earth) cycles.
For more information about how these predictions were calculated, please contact Matthew Widlansky.
To receive updates when the latest tide predictions are generated, subscribe to our email updates. To subscribe, send an email to: firstname.lastname@example.org.
For each day, highest and lowest† hourly water levels, along with the daily range averaged during the epoch.
For each month, highest and lowest† hourly water levels, along with the monthly maximum range averaged during the epoch.
Highest and lowest monthly mean water levels, along with monthly data averaged during the epoch and for each selected year(s).
Displaying all plots in one figure.
†For user-selected years, only the highest water levels are shown in graphs of daily and monthly extremes.
This product provides a preliminary look at the recent or past water levels compared to the long-term records and climatology at the tide gauge station. Updates are typically available by the 15th day of each month using the UHSLC’s Fast Delivery of tide gauge data.
Three plot types (Daily Extremes, Monthly Extremes, and Monthly Means) are provided with the first two utilizing hourly data and the latter monthly data. In the Daily Extremes plot, the sub-monthly oscillations are due to the spring-neap tidal cycles (i.e., new or full moon phases) combined with independent sea level variability on lower or higher frequencies. When viewing individual years of daily extremes, note that days with partial missing data will sometimes show a spike well below the typical spring-neap tidal cycle that explains the normal oscillatory nature of the records (e.g., if that day’s highest tide was not recorded).
Similar types of graphical displays are available on the web for many other types of atmospheric and oceanic data, including a water level visualization for Miami, Florida, which helped inspire this product.