West Coast Tide Corrections: Are They Correct?
One of the differences between sailing in Northern and Southern California is the difference between tides and currents. Southern California has somewhat smaller tidal differences and almost no current. Wherever you’re racing, if there’s current you should pay attention, but its impact in San Francisco Bay racing is far greater than in Southern California racing. Regardless, we always like to pick up a tide book to check out the local ebb and flow. We became puzzled on page one.
The tidal correction chart shows Los Angeles at zero correction and then, as you progress north, minutes are added along the way. Until you get to San Francisco and then, for some reason, the progression of minutes being added drops about an hour at Pt. Arena, before it resumes having minutes added as you head north. Are we missing something obvious?
San Francisco tide could be expected to be delayed from tide outside or near the Golden Gate. But I’m not saying any of those corrections are right.
Probably should read 2.15 instead of 1.15. Proofreading and checking your work is becoming a lost skill these days.
Pretty soon all communication will be in abbreviations which you then need to Google to understand what they mean.
Good eye for catching subtle details!
I suggest referencing NOAA Tide Predictions at their web site https://tidesandcurrents.noaa.gov/tide_predictions.html?gid=1393
There is a tremendous amount of valuable information published on this web site, including graphs comparing actual tidal height measurements compared to predicted heights.
The NOAA tide prediction application confirms the approximate 60 minute difference in high tide times between Pt. Arena and SF Gate. Your tide book offset is not an error.
I suspect the difference in max and min tide at SF Golden Gate and other coastal locations is the time delay or damping effect with SF bay and interior water volume change per foot of surface elevation change at the bridge. Tidal elevation change has to fill or drain SF Bay interior volume before the elevation will change at the Bridge. This filling or draining takes time, about sixty minutes difference w/r Pt. Arena.
Thanks for this timely reminder to check the tides now since the next few days will be the most extreme of the year. Normally I am in So. Calif. but tomorrow I will be taking a Sunday drive to check out Humboldt Bay as close to dark as I can see anything. I expect much of the bay will be ‘land’. The lowest is Tues. [-1.87′] but it will be an hour or so after dark. Not a good time to be stuck in the mud.