Observed Current Arrows
Direction arrows from measured satellite current. Direction only and no speed — use a current speed layer for that.
Updates daily
More detail
It is what the Currents button on the bottom bar shows while the Observed tab is chosen in Data Layers, on the iPhone app and the website. Tap Currents and moving arrows or streaks run the way the water is moving. Switch Data Layers to the Forecast tab and the same button automatically follows the HYCOM (U.S. Navy model) forecast current instead.
Where the current comes from. Radar satellites measure the height of the sea surface, and the current is worked out from its slope once a day. It arrives about a day behind. The Copernicus Marine Service, the European Union's ocean data service, makes it, and it is the same measured current that the Currents (DUACS) layer colors by speed.
What it leaves out. It leaves out wind push and tide, so it runs smoother than the forecast current, which includes them. Neither will match your drift exactly. Each cell is about 8 nautical miles across, against about 5 for the forecast, so it shows the Loop Current and the big eddies and not a rip or a tide line. It is least trustworthy close to the beach, and it is the surface only, whatever depth the map is set to. The streaks cover the Gulf of America, the East Coast and Baja.
When to use which. Use this measured current to check that an eddy or a current edge the forecast shows is really there. Use the forecast current, on the Forecast tab, for the tide, the wind's push, depths below the surface and the days ahead. To see how fast the water is moving, put up Currents (DUACS) or Currents (GlobCurrent). Those color the water by speed and show no direction. The streaks on the Observed tab always follow the Currents (DUACS) current, even when Currents (GlobCurrent) is the layer on screen.
If the streaks are missing on the Observed tab while the forecast ones work, step the date back a day.
The numbers
| How often it updates | Once a day |
| How fresh it usually is | About a day behind |
| How detailed it is | About 8 nautical miles per cell |
| Where it covers | Gulf of America, East Coast and Baja, surface only. Least trustworthy close to shore |
| Observed or modeled | Observed by satellite |
| What you see on screen | Moving arrows or streaks drawn by the Currents button, with the Observed tab chosen in Data Layers. Direction only |
Source: computed by RipIQ from DUACS satellite currents (Copernicus).