1. How do I read these graphs?

The answer is a little complicated but we'll try to keep this as brief and informative as possible.

Buoys help serve as indicators or "predictors" of swells heading towards, away, and sometimes parallel to the coastline. Interpreting buoy observations requires at a minimum knowing where each buoy is located relative to your surf spot. We currently monitor these buoys, where NM means Nautical Miles:

Because buoys are separated from one another by distance, they can sometimes each tell a different story in terms of their own local conditions (swell height, wind, etc). Making sense of this becomes easier if we think about how long it takes swells to reach the coastline from each buoy. Swell period and angle each affect the timing of swells from buoys to land, but roughly speaking for a solid (17-second) interval swell coming from the northwest, it takes about 24 hours to get here from SE Papa buoy and 12 hours from California buoy.

Now let's talk specifics about the graphs.

The graph on the left shows how to read the time information. The latest buoy reading was taken at 7am on October 3rd. Each block on the horizontal x-axis represents 24 hours, whereby Noon is in the middle (gray tick mark). Approximately 5 days worth of data is shown.

Wave Height represents the average of the highest one-third of all of the wave heights passing by the buoy during a 20-minute time span. Wave Period represents the period of the strongest wave energy, which roughly means the time interval between the largest swells passing by the buoy. Wind Speed is the average wind speed over an eight minute sampling period.  As you can see in the graph to the right we combine wind speed (thin vertical bars) with wind direction (colors) over a five-day time span.

Wind Direction is based on a compass where zero and 360 degrees represent due North (i.e. wind blows from north to south). We don't show wind direction explicitly but instead color code this into the graph. The colors are oriented to reflect good and bad winds, where "good winds" (green) are offshore and "bad winds" (red) are onshore. The angles used to determine good and bad are optimized somewhat for conditions at Ocean Beach, SF. For buoys far out to sea (e.g. SE Papa) wind direction might not matter too much, but for inshore buoys (e.g. SF Buoy) this data is more meaningful.

2. What do these graphs not show?

3. Tell me more about timing.

Swells moving toward the coast tend to show up as successive "humps???" in our graphs. The examples below show a typical pattern whereby a swell peaks on SE Papa (far out at sea) and some time later we see a rise on the near shore buoys.

4. How accurate is this information?

It is worth noting that rapidly changing sea conditions, observation anomalies, and/or transient instrumentation failures can cause odd features in the graphs. As such, interpret this data with a grain of sea salt.

5. Can you add graphs for other buoys?

Maybe....