Currents (button)
Draws measured satellite current as moving particles over whatever layer you have up — which way the water sets and roughly how hard. In forecast mode it follows the forecast current instead. No speed scale, and it turns off each time you open the app.
Updates daily; forecast in 3-hour steps
More detail
How to turn it on. Currents is a button on the bar along the bottom of the map, on the iPhone app and the website. Tap it once and arrows or streaks, the moving particles named above, start to drift across the water. Tap it again to remove them. Each streak has a bright head and a fading tail and runs the way the water is moving. Streaks move faster where the water runs harder.
Which current you are looking at. The button automatically follows the tab you choose in Data Layers. The map opens on the Observed tab, where the streaks follow a current worked out from satellite measurements: one picture a day, surface only, about a day behind. On the Forecast tab they follow the HYCOM (U.S. Navy model) forecast, in three-hour steps, from 8 days back to 7 days ahead. The measured current carries only the flow driven by the slope of the sea surface and leaves out wind and tide. The forecast includes them.
Depth. On the Forecast tab the streaks follow the map's depth setting where a current exists for it: the surface and 82, 164, 328, 492 and 656 feet. At any other depth they show the surface flow. On the Observed tab they are always the surface.
For a speed in knots, use a current layer. The current layers in Data Layers color the water by speed and show no direction: Currents and Currents at Depth on the Forecast tab, Currents (DUACS) and Currents (GlobCurrent) on the Observed tab. Put one of them up with the Currents button on and you have color for how fast and streaks for which way.
Limits. Each forecast cell is about 5 nautical miles across and each measured cell about 8, so the streaks show the big flow: the Loop Current, the eddies, the general set. They do not show a rip or a tide line you could see from the boat. If the streaks barely move inshore or at the turn of the tide, the water really is slack. The streaks cover the Gulf of America, the East Coast and Baja only.
Fine-tuning. With Currents on, a small wrench appears above the button. It opens the particle settings. If the streaks look wrong after you have changed them, tap "Reset to Defaults" there. The Currents animation article covers the streaks and those settings.
Who makes it. The measured current comes from the Copernicus Marine Service, the European Union's ocean data service, and the forecast current comes from HYCOM (U.S. Navy model). The moving streaks are RipIQ's own drawing of that data.
The numbers
| How often it updates | Once a day on the "Observed" tab, where the map opens; every 3 hours on the "Forecast" tab |
| How fresh it usually is | "Observed": about a day behind. "Forecast": the newest frame is from a run started between one and four days ago |
| How detailed it is | About 5 nautical miles per cell on "Forecast", about 8 on "Observed" |
| Depths | "Observed": surface only. "Forecast": surface, 82, 164, 328, 492 and 656 feet |
| Where it covers | Gulf of America, East Coast and Baja only |
| How far back you can look | 8 days back |
| How far forward you can look | Up to 7 days ahead, on the "Forecast" tab |
| Observed or modeled | Satellite-observed on the "Observed" tab; modeled on the "Forecast" tab |
| What you see on screen | Moving arrows or streaks showing direction and relative speed |
Source: computed by RipIQ from the DUACS satellite altimetry current on the Observed tab, and the HYCOM model current on the Forecast tab.