These surface current overlays provide maps of 25-hour averages. This means that for any given hour, the data are averaged over ±12 hours. For example, a 25-hour average at 12 pm (noon) would average together the data at noon along with the previous 12 hours (midnight to noon) and the following 12 hours (noon up to and including midnight of the following day) for a total of 25 hours averaged together. By smoothing out the hourly variability in this way, one can view the surface currents with less influence from the tides.
note: Because a 25-hour average must average together the 12 hours after the selected time, the most recently available map will lag 12 hours behind the present.