Hi -

the most extreme tides (highest & lowest) of the season are coming up - great times to go tide-pooling or to watch the bluffs recede. The really high tides in conjunction with a good storm surge can produce something to behold, and a good low tide at sunset on a clear cold winter day, well, that’s reason #3 of why we live here - starting on the Solstice and continuing until the day after Christmas, something to take the out-of-towners to see!

and as always, if you’re out in the tide pools - beware of the very ral danger of sneaker waves - a good safety primer is avaialble here:
http://coastguardnews.com/coast-guard-urges-beach-safety/2006/12/08/

and good comcise explanation of how it all works can be found at NOAA’s “ A BRIEF EXPLANATION OF THE BASIC ASTRONOMICAL FACTORS WHICH PRODUCE TIDES AND TIDAL CURRENTS” at

http://www.co-ops.nos.noaa.gov/restles1.html

Chuck Kozak

* - Just the highest and lowest of each day listed -

12/21/2007 Fri

08:16AM LST 6.9 H
03:22PM LST -1.2 L

12/22/2007 Sat

09:04AM LST 7.1 H
04:11PM LST -1.6 L

12/23/2007 Sun

09:53AM LST 7.2 H
04:59PM LST -1.8 L

12/24/2007 Mon

12:24AM LST 5.0

10:42AM LST 7.1 H
05:46PM LST -1.7 L

12/25/2007 Tue

01:11AM LST 5.1

11:32AM LST 6.9 H
06:32PM LST -1.5 L

12/26/2007 Wed

12:22PM LST 6.5 H
07:18PM LST -1.1 L

Thanks for the excellent suggestion.  It has been too long since I last visited Fitzgerald and now would be a great time to do it. And bring the kids, of course.

By the way, we’re now running a feed of the day’s tides toward the bottom of the right-hand column on Coastsider.

Thanks Barry - And I forgot to mention that the tide times listed are for San Francisco at the Golden Gate - for Half Moon Bay (the actual bay, not the town), the rough adjustment is to subtract 1 hour: -66 minutes for high and -50 minutes for low if you want to get particular.

A minor aspect of this is that there are/were some good afternoon hours for photography in the low intertidal on Friday, Saturday, Sunday, and even toward the end of the afternoon on Monday. It is also interesting to pick a place that is dramatically different with more than an eight-foot difference in sea level and shoot it at high and low tides from the same tripod holes.

Carl May

Chuck, could you clarify the adjustment?  The feed is showing high tide at 12/22 7:57 AM and your original post lists it at 12/22 9:04 AM.  You say “subtract 66 minutes” but the way I look at it, 7:57 AM <u>plus</u> 67 minutes is 9:04 AM.  To be clear, are the high & low tides here approximately one hour <u>later</u> than the times given in the feed, as you show, or one hour <u>earlier</u> as your followup text seems to be saying?

Leonard -

Yes, to clarify, I meant subtract (turn the clock back) 66 minutes from the times I had originally posted (which were for the Golden Gate), not from the feed shown on coastsider. Barry’s feed (which is already adjusted for Half Moon Bay). So 9:04 AM - 66 minutes = 7:58 AM.

Just to be clear, full tide table or 2007, adjusted for Half Moon Bay, is here

chuck

quote author=“Carl May” date=“1198332287”]” ... A minor aspect of this is that there are/were some good afternoon hours for photography in the low intertidal on Friday, Saturday, Sunday, and even toward the end of the afternoon on Monday…”

It is indeed a good time for tidepool photography - the low sun helps eliminate a lot of the glare & reflection problems, and there is access to some of the farther out sections where the less-observed lower-intertidal animals can be found.

I have a fast (f1/8) short focus (0.3 m) 35mm lens that I use with a focal-length doubler (effective 70mm) - with 200 ASA or higher film and a steady hand, you can get good close shots of even the small nudibranchs with a resonable depth of field and without dipping your lens into the water. Its a good setup for shooting wildflowers, too.

A note from personal experience: Watch out for the waves and tide turnarounds - its unpleasant and dangerous to get stuck out there. Bring a friend who can act as a wave spotter, so when you’re lying on the rocks trying to focus on that little crab you don’t get surprised.

For any other “visual learners” out there, this site shows flood/ebb, day/night in a graphical format

http://www.mobilegeographics.com:81/locations/2364.html

Enjoy :-)

I will say that we walked around that flat walk to the Mavericks area and I could not believe how far out the tide was this afternoon. You could walk all the way out to the large rocks, it was amazing. There were a good number of people out there exploring the tide pools. It was my first time seeing it like that in the five years I have lived here. I only wished we would have been at the Marine Reserve but it is hard to get my baby stroller down there.

-GraceAnn

Speaking of tide tables, owners of Palm PDAs (including Treo) should install the excellent (and free) Tide Tool:

http://www.toolworks.com/bilofsky/tidetool/

It has nicely presented tide data, as well as sunrise, sunset, moonrise, moonset and moon phases.

Did anyone “watch the bluffs recede”, as Chuck suggested, during the recent storm?

I recommend “Living with the Changing California Coast” by Gary Griggs, Kiki Patsch, and Lauret Savoy, published by University of California Press, ISBN 0-520-24445-1 (cloth) or 0-520-24447-8 (paperback), for an understanding of the mechanisms of seacliff or bluff erosion (as well as many other coastal processes). Individual chapters cover all 1100 miles of the California coast in some detail, showing average annual erosion rates, with many illustrations. The San Francisco to Ano Nuevo chapter (written in part by Ken Lajoie from the United States Geological Survey, whom many of us know from his presentations to the Midcoast Community Council) gives information of local interest.

Example: Ten homes along Esplanade Drive in Pacifica were demolished in April 1998, where average erosion rates are about 18 inches per year, when a severe storm caused approximately 40 feet of bluff to collapse over a short time period. This was despite a revetment installed to protect those homes. This also illustrates how bluff failure is typically episodic, with long periods of stability followed by significant loss under severe storm conditions.

Example: Bluff erosion during the winter of 1983 threatened the former Chart House Restaurant in Montara, resulting in placement of extensive riprap.

Example: Erosion rates at Surfer’s Beach in El Granada, which had averaged a few inches per year under natural conditions, increased to as much as 80 inches per year after the Pillar Point Harbor breakwater was built in 1959. This illustrates how inadequate understanding of coastal dynamics led to unintended consequences, as the wave refraction pattern around Pillar Point was disturbed.

Those are just a few of the locations where you might see receding bluffs, either from this storm or others to come.