This page provides background information for the plots on the plots page. The tide level at the Palo Alto Baylands Sailing Station, like other sites, is often significantly different than the published tide predictions. The tide levels are affected by the winds, rainfall, and atmospheric pressure. The first plot (shown below) on the plots page shows current measurements of the tide level for the Palo Alto Baylands Sailing Station dock with green '+' symbols. The dark violet line in the plot shows the predicted tide levels for the Palo Alto Yacht Harbor. The light blue line in the plot shows the safe foiling tide level. The tide level for the mud on the south side of the stream channel that runs past the front of the dock is shown with a gold line. These four lines and symbols are describe in more detail in the sections below. The next three plots on the plots page show the NOAA San Francisco Bay Operational Forecast System (SFBOFS) hydrodynamic model predictions of the tide levels within a few miles of the Sailing Station dock. These plots show NOAA's best predicition of the tide levels that are created by a state-of-the-art hydrodynamic model that includes the effects of winds, atmospheric pressure, and rainfall. The SFBOFS predictions are also describe in more detail below. The final three plots on the plots page show the measured tide levels for yesterday, the day before yesterday, and the last seven days at the Palo Alto Baylands Sailing Station dock. These seven plots are presented together on the plots page to help sailors quickly predict when there will be enough water at the Palo Alto site to safely wingfoil and have a good sailing session.
Most sites use tide predictions that are based on a set of harmonic constants that define a set of sine waves that are added together to predict the tide level as a function of time. There are harmonic constants for each tide location that are defined by analyzing many years of tide level measurements. NOAA use 17 years of data for finding its harmonic constants. This page and the main plots page. use the the XTide 2 program to predict the tide levels for the Palo Alto Yacht Harbor (dark violet line in the plots). XTide uses harmonic constants. XTide is used by many sites, including iKITESURF, for their tide predictions for the Palo Alto Baylands Sailing Station. XTide runs very quickly and uses minimal computational resources.
In addition to the standard harmonic constants based tide predictions, NOAA uses a supercomputer with the San Francisco Bay Operational Forecast System (SFBOFS) to make tide predictions using a hydrodynamic model that includes the influence of winds, barometric pressure, and stream flows. The main plots page includes three NOAA SFBOFS plots with predicted tide levels for Coyote Creek, Dumbartan Bridge, and the Port of Redwood City. The Port of Redwood City predictions are included because this is the closest SFBOFS site with observed tide levels (red '×' symbols in the plot below) included in the SFBOFS Port of Redwood City plot. The harmonic constants based predictions are shown with a blue dashed line in the SFBOFS plots. These observed tide levels are useful for assessing the accuracy of the SFBOFS and harmonic constants models. The SFBOFS model is run every 6 hours and shows the Nowcast for the previous 24 hours and the Forecast Guidance for the next 48 hours. The Nowcast is created by using available measured data to estimate the tide levels for the past 24 hours. The Nowcast is NOAA's best estimate of what the tide levels have been for the last 24 hours.
When I first wingfloiled at the Palo Alto site on July 17, 2025, Bill Keeting told me that it was safe to foil there when the water is at or above the bottom of the collar on base of the electrical power lines tower closest to the dock. I have determined that this is approximately a tide level of 6.8 ft. As the tide goes out, the mud first shows on the south side of the creek channel that runs in front of the dock about 50 ft north east of the north end of the dock. I estimate the tide level to be 3.2 ft when the mud first becomes visible on a receding tide. Both of these levels are shown in the plots.
Hint: Clicking on an image opens a larger image in a new browser window.
The City of Palo Alto's Creek Monitor and Camera page includes a Creek Monitor image that has the tide level measured at the Flood Basin Tide Gate Structure which is located 220 yards south of the southernmost end of the Baylands Sailing Station dock. Tide predictions we are all familiar with are given relative to Mean Lower Low Water (MLLW). The MLLW is the average of the level of each day's low tide and is assigned to be 0 ft. The reported "Tide" level in the Creek Monitor image is not relative to the MLLW level but some other reference that I have not tracked down. Fortunately I found a National Ocean Survey Bench Mark and was able to use it to calibrate the Creek Monitor Image tide levels. The Survey Bench Mark is located about 380 feet north east of the old Sea Scout building. This building is now now known as the Environmental Volunteers EcoCenter. The next four images below show the Survey Bench Mark and its location.
The National Oceanic and Atmospheric Administration (NOAA) Bench Mark Sheet for 9414525, PALO ALTO YACHT HARBOR, S. F. BAY CA says that bench mark with stamping 4525 C 1976 is located at 9.65 ft (2.940 Meters) above MLLW. Using this information, a laser level, and a tape measure, I was able to calibrate the Flood Basin Tide Gate Structure "Tide" measurement to be 3.22 ft below tide levels given relative to MLLW. The Flood Basin Gauge values in the plots on this page are created by adding 3.22 ft to the "Tide" value extracted from the Creek Monitor image.
As many sailors have observed, the water often comes in early and leaves early. Sometimes as shown in the plot below, the predictions do a reasonably good job of predicting the high tide levels and timing. Only after seeing the data plotted up for a bunch of days did I realize how much more water comes in than is predicted. Some days the tide comes in an hour earlier than predicted and can be as a full foot higher than predicted. Hopefully having real time data will help us all get in more time wingfoiling and windsurfing. I suspect that, with time, I will refine and adjust how I make these plots and the tide levels I show in the plots for Foil Safe and mud first visible tide levels.
Ken Poulton and I started tracking the tide levels at Palo Alto in August of 2025 by taking photos. Yomi Matsuoka joined in on the tide characterisation effort by taking pictures and giving them to Ken and me. Ken saw that the ladder at the base of the power lines tower is a "ready-made gauge". This breakthrough enabled us to easily assign heights to the observations. Ken was the first to plot these observations with the xtide predictions and determine that a better scale was to assign 9 to the top step rather than 8. My wife and I found Bench Mark 4525 C 1976 while on a walk on October 26, 2025. Two days later, I swam my board to the ladder and measured the step spacing on the ladder to be 15 inches. On October 29, 2025, I inquired at the Palo Alto Baylands Ranger Station to find out if there was a tidal gauge on a pier or pole in the water somewhere that we could use to determine the tide level. To my delight, the lead ranger showed me the Creek Monitor and Camera page on her computer. She also told me that the tide level reported in the Creek Monitor image was offset by two feet from the actual tide level. That same day, I used a laser level and a tape measure to calibrate the tide level relative to the Bench Mark 4525 C 1976. I computed the offset from the Flood Basin Gauge to be 3.22 ft rather than the 2 ft that the lead ranger told me. On November 5, 2025, I remeasured the offset to be 3.21 ft. It could be the real offset is 1 meter (3.28 ft) but since my measurements were so consistent, I am using my first measurement of 3.22 ft.
Michael Schuh
Version 1.2 2025-11-24