Guide · two minutes · no math degree required
How to read the buoy for a Florida beach
NOAA's National Data Buoy Center (NDBC) runs the buoys every spot page here links to. The station page shows a table of the latest readings. Four numbers matter for surf; here is what NOAA says each one is.
| Column | NOAA's definition | What to do with it |
|---|---|---|
| WVHT wave height | "Significant wave height (meters) is calculated as the average of the highest one-third of all of the wave heights during the 20-minute sampling period." NDBC, Measurement Descriptions and Units | Metres. Multiply by 3.28 for feet. It is measured out at the buoy, not on the sandbar. |
| DPD dominant period | "Dominant wave period (seconds) is the period with the maximum wave energy." NDBC, Measurement Descriptions and Units | Seconds between the waves carrying the most energy. Longer usually means swell from far away; short means local wind chop. |
| APD average period | "Average wave period (seconds) of all waves during the 20-minute period." NDBC, Measurement Descriptions and Units | Compare with DPD: a long DPD over a short APD means a swell under the chop. |
| MWD wave direction | "The direction from which the waves at the dominant period (DPD) are coming. The units are degrees from true North, increasing clockwise, with North as 0 (zero) degrees and East as 90 degrees." NDBC, Measurement Descriptions and Units | Hold it against the spot's compass. Inside the dark blue wedge: square on. Inside the pale wedge: angled. |
| WDIR / WSPD wind | Wind direction is given the same way, as the direction it comes from, with speed in metres per second. NDBC, Measurement Descriptions and Units | Wind from the spot's orange "offshore" side grooms the waves; wind from the sea side blows them out. |
Swell and wind waves, separately
NOAA: "NDBC also provides estimates of the height and period of wind-seas and swell on each station page by applying the above process to the respective wind-sea and swell portions of the wave spectrum." NDBC, How are significant wave height, dominant period, average period, and wave steepness calculated? On a station page that is the "Detailed Wave Summary": swell height (SwH), swell period (SwP) and swell direction (SwD), next to the wind-wave versions (WWH, WWP, WWD).
Holding it up against a Florida beach
- Open the spot page and note the facing, for example Sebastian Inlet, First Peak (north jetty) faces 64° (ENE).
- Open its buoy (here NDBC 41114, 40.2 km away) and read MWD. Within about 35° of the facing is square on; within about 80° can still wrap in.
- Read WVHT and DPD together. Bigger and longer is more energy. The buoy sits offshore, so the beach can be smaller, especially where shoals or islands are in the way.
- Read WDIR. From the land side is offshore; from the sea side is onshore.
- Check the NWS surf zone forecast for rip current risk, then the tide, because some spots here are quoted as working best on a particular tide.
The "what to do with it" column and the steps are our reading of NOAA's definitions, not NOAA's advice. Sources, read 2026-11-03: NDBC, "Measurement Descriptions and Units"; NDBC, "How are significant wave height, dominant period, average period, and wave steepness calculated?".