Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

[Phys-l] One half of a tide?



Yesterday I just happened to pick up a tide table for the Ventura area (where our vacation single-wide is located) and noticed what I was initially quite certain was a mistake. The tide table indicates that the usual two tides (four tidal extrema) a day routine would be disrupted this Friday (August 14, 2009.) On that day there the table indicates no low tides at all and only one high tide in the late afternoon. That is, the prediction is for just one half of "a tide" on Friday. It turns out that the tide table is correct. The following link to a graphical tide table shows how it works:

http://www.freetidetables.com/state/California/sid/14557594

Notice that Friday happens to be one of the very rare days when the lower high tide (in the wee hours) happens to be lower than the higher low tide (at dawn). But compounding the rarity even further, the previous low tide occurs at 11:23 PM on the 13th (37 minutes before the 14th begins) and the next low tide occurs at 12:39 AM on the 15th (39 minutes after the 14th ends.) The result is a single tidal extremum at 4:19 PM on the 14th.

John Mallinckrodt
Cal Poly Pomona