Great Neck Bridge, Broad Bay
Extratidal Water Level: 36-Hour Forecast
Click on any item in the chart legend above to hide and show that particular data trace.
Last 30 days | Last 3 days | 36-hour Forecast
Legend Definitions & Datum
Sensor Observation (dashed = forecast)
The solid red line shows the observed water level (unverified data from the U.S. National Oceanic and Atmospheric Administration). The dashed red line shows our water-level forecast for the next 36 hours.
Predicted Astronomic (m30) Tide
The blue line shows our prediction of the astronomic tide. This incorporates two factors:
Residual (dashed = forecast)
The green line is the residual difference between the predicted astronomic tide and the observed water level. Values are positive when observed values exceed predicted values, and negative when observed values fall below predicted values. The solid green line shows the observed residual; the dashed green line shows our forecast for the residual over the next 36 hours.
Observed and predicted water-level values are displayed in feet and referenced to the elevation benchmark North American Vertical Datum of 1988 (NAVD88). This is the datum in which house and road elevations are typically given.
For a more detailed discussion, visit the Tidewatch Background page.
The Virginia Institute of Marine Science (VIMS) makes no warranty concerning any of the data displayed on this website (www.vims.edu/tidewatch). Read our Disclaimer and Methods Disclosure statement.