This is a map of the magnitude of the horizontal velocity of the seawater at the indicated depth. Units are meters per second.
RTOFS (Atlantic) is a basin-scale ocean forecast system based on the HYbrid Coordinate Ocean Model (HYCOM). RTOFS (Atlantic) is described in the following paper (PDF): "A Real Time Ocean Forecast System for the North Atlantic Ocean" by Mehra and Riven, Terr. Atmos. Ocean. Sci., Vol. 21, No. 1, 211-228, February 2010
The model is run once a day, completing at about 1400Z. Each run starts with a 24 hour assimiliation hindcast and produces ocean surface forecasts every hour and full volume forecasts every 24 hours from the 0000Z nowcast out to 120 hours.