Predict Tides at Your Favorite Coastal Spot
 
questions
"lingo"
web links
activities
visuals
home
prev. topic
  • You can make tide predictions using data from the Internet
  • Learn how tide predictions at many "subordinate" stations are tied to a limited number of reference stations
   

The Oceanographic Products and Services Division website allows you to predict coastal tides.

  • Follow these steps to predict tides on your favorite part of the coast:
    • Using an atlas, identify your favorite spot on the U.S. coast.
    • Visit the "Make a Tide Prediction" webpage.
    • In the left column, U.S. coastal states will be listed. Choose your U.S. state (or coast in U.S. territories).
    • You will see a list of coastal areas in that state or territory. Click on the station located closest to your favorite coastal spot.

A graph of data will show predicted (blue) versus observed (red) water levels (WLs). The green line shows the difference between these WLs. If the predicted and observed WLs matched exactly, then the green line would equal zero over the time period shown.

To see "Tide Predictions" for this station, click on the button in the lefthand column. You can change the start and end dates using the "pull down" menus at bottom.

Data tables are commonly used to predict tides. Click here to see an example of how to use data tables to predict coastal tides.

  • Become comfortable reading tide prediction tables
  • Reserach how to find high and low tidal ranges
  • Using the Internet to correlate tidal ranges with lunar phase
  • Are "spring tide" and "neap tide" really tied to the moon?
  • Consider the importance of being able to accurately predict tides
  1. Click here to access the July 1998 data for the Portland, Maine reference station. Note that, in this example table, high tide data are shown in red.
    • Did everyday in July 1998 have two low tides? Two high tides?
    • Randomly choose five dates in July 1998. If those dates had two high tides, what was the difference between the higher high tide and the lower high tide?
      • Was the variation between subsequent high tides greater than, less than, or about 2 feet?
      • Does this variation in the two daily high tides put Portland Maine's coast into the diurnal, semidiurnal or mixed tide type?
        • Click here to see the water levels associated with these tide types.
  2. The DIFFERENCE in the height between consecutive high and low water levels is known as the tidal range.
    • Is the date with the highest tidal range called a spring tide, a neap tide, or neither?
    • For the July 1998 Portland Maine data, find the date / time with the highest tidal range:
      • Begin by finding the relatively high values for high tide (in this case, these values are greater than 10.5 feet)
      • Then look at the values for low tides before and after these relatively high tides (in this case, the values are LESS THAN ZERO).
      • The tidal range is the difference been these numbers.
        • For example, on Saturday, July 11th the high tide at 12:31 A.M. was 10.5 ft
        • The next low tide (at 6:54 A.M.) was -.5 ft
        • The tidal range for this example is 11 ft [= 10.5 - (-.5)]
          • [By the way, this is NOT the highest tidal range for July 1998!]
    • To which lunar phase do you think the date / time of the highest tidal range corresponds?
      • Check your answer against a source that has lunar phase information.
      • For example, visit the U.S. Naval Office's "Virtual Reality Moon Phase Pictures" website.
        • Enter data to get a lunar phase image for:
          • The current time (updated every four hours); or
          • Any hour for dates from 1800 A.D. to 2199 A.D.
          • Be sure to choose "Eastern Time" for this example.
      • Did the highest high tide match with the lunar phase you predicted?
      • Can you guess why or why not?
  3. If possible, compare your "favorite spot's" tide prediction to that from a local newpaper.
    • Does your prediction match theirs?
    • How do you suppose they predict tide levels?
  4. Consider the data tables used to predict tides.
  5. Knowledge of the times, heights, and extent of inflow and outflow of tidal waters is of important for many maritime activities.
    • Can you list activities that might benefit from tide predictions?
  • datum
  • diurnal tide
  • lunar phase
  • mixed tide
  • neap tide
  • reference station
  • semi-diurnal tide
  • spring tide
  • subordinate station
  • tidal range
  • tide prediction
 
  • None
   
prev. topic
"info"
questions
"lingo"
tides home
"Virtual"
Bigelow