Retention Zones

More detail

What you see. 1.0 is dead still water, and fast water reads 0. A color means about the same water speed from one day to the next.

How to use it. Look offshore for a bright patch that holds across several frames. In Layer Settings you can change the Colormap and the Opacity.

How it relates to the other layers. Currents shows the speed itself, so slow water on Currents is bright here. Use Currents to see the whole flow, and Retention Zones to pick out the slack water at a glance. Surface Convergence shows where water is squeezing together. FSLE 7-day follows the water over a week to trace the lines where drifting things gather. This layer shows the speed at one moment.

Who makes it. RipIQ makes this layer itself from the forecast surface current of HYCOM (U.S. Navy model). The layer covers the Gulf of America, the East Coast and Baja.

Its limits. It is a snapshot of speed, not a measure of how long water stays, so steady slow water moving one way still rates high. The tide moves the pattern between frames. It paints right up to the beach. The bright band close inshore is slow, unreliable forecast current. A small slack pocket may not show. There are eight frames a day, three hours apart. The newest frame is from a run started between one and four days ago, and the time slider reaches up to 7 days ahead as a forecast.

The numbers

How often it updates	8 frames a day, three hours apart
How fresh it usually is	The newest frame is from a run started between one and four days ago
Where it covers	Gulf of America, East Coast and Baja only, right up to the beach
How far back you can look	8 days back
How far forward you can look	Up to 7 days ahead, as a forecast
Observed or modeled	Calculated by RipIQ, from HYCOM (U.S. Navy model)
What you see on screen	A 0-to-1 scale with no units

Source: computed by RipIQ from HYCOM model surface currents.