Confusion with Maine Harbor Tide Chart

[cow tamer]

The PM low tides never seem to follow a typical pattern. Aug. 18th is listed as a dash (what ever that means) and then the 19th is 1/2 hr. earlier than the 16th and it has an asterisk near it. This happens month after month. The other tide times seem to make more sense and follow an expected pattern.
Can anyone explain.

[JFigliuolo]

I'll try.
1. The - means there is no PM low tide. The next low tide happens after midnight ie.
8/17 second high is 4:11 PM, the next low is 8/18 at 12:06 AM (a little after midnight)

2. The * means the second low tide in the series occurs in the AM, rather than the PM. ie.
8/18 first low at 12:06 AM, First High at 4:39 AM, second low at 10:42 AM. Normally the second tide would be in the PM, but for a few days a month, it is in the AM. Thus the *.

Hope this explains things a little.

[Raven]

politics to me....

[Bill L]

You can click on the linke "* AM tide see Note " at the bottom of the chart for an explanation. Not sure if it will paste here>>>>

On average, the recurrence of a tide of the same phase and similar rise takes place at an interval of 24 hours 50 minutes after the preceding occurrence. (If it's high at 3pm today then it'll be high tomorrow around 4.) This is, however, only a monthly average. The relative positions of the sun, moon and earth at different times during the month can significantly alter this interval and the "expected" times of high and low tides.
Between the new moon and the 1st quarter and between the full moon and 3rd quarter there is an acceleration in tidal arrival times. Between the 1st quarter and the full moon and between the 3rd quarter and the new noon there is a delay.

One of the occasional results can be two AM or PM high or low tides. This is particularly likely to occur in Buzzards Bay and Narraganset Bay because of the unique coastline configuration, water depth, and ocean-floor topography of that area. However, it can occur at any location.

Here are Newport RI tides for May 24-26, 1999. Notice the two AM low tides on the 26th.



On our tide charts we indicate this AM or PM anomaly with a red asterisk - * - and a note at the bottom of the chart as shown here:



DATE HIGH LOW
AM hgt PM hgt AM hgt PM hgt rise set qtr

24 Mon 4:10 3.3 4:40 3.7 10:37 0.5 11:28 0.5 5:19 8:06
25 Tue 5:03 3.3 5:29 3.8 11:21 0.4 - - 5:18 8:07
26 Wed 5:51 3.3 6:14 3.9 12:14 0.4 11:56* 0.4 5:17 8:08

[cow tamer]

Thanks for the explanation. I'm sure the - & * don't bother the fish all that much.