Sea Level Anomaly

More detail

What you see. A closed patch of red or blue is the body of an eddy, and white is water standing close to its usual height. The colors are centered on the day's average for the whole basin. The color scale runs to about 18 inches (0.45 meters) either way, and Loop Current features can go past the end of it. On the website the crosshair readout gives the height in whole inches when your depth unit is feet, and in meters otherwise.

How to use it. Use the layer to find the big features and to tell warm from cold. In Layer Settings you can change the Colormap, the Range and the Opacity.

How it relates to the other sea level layers. SSH - Altimetry is the same forecast shown as the height itself. SLA (DUACS) is the measured counterpart. It comes from satellites, has the tide taken out, is about a day old, and shows the big features only, about 95 nautical miles across and larger. Use SLA (DUACS) to see where the big eddies were measured to be, and use this layer for finer detail and for the days ahead. Eddy Probability marks the sharply curved middle of a feature without saying warm or cold. Cyclonic Velocity Front (Cold-Core Rim) and Anticyclonic Velocity Front (Warm-Core Rim) mark the fast rim. On the Forecast tab the Altimetry button draws contour lines traced from this same layer.

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

Its limits. It is a forecast, so the placement of a feature on a given day can be off. The average has no seasons in it, so a normal seasonal rise or fall reads as an anomaly. The tide is still in it, so compare the same time of day from one day to the next. 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
How detailed it is	About 5 nautical miles of real detail
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, as a forecast
Observed or modeled	Calculated by RipIQ from the sea surface height of HYCOM (U.S. Navy model)
What you see on screen	Height above or below the long-term average. Red is high, blue is low, and white is centered on the day's basin average. On the website the readout is in whole inches if your depth unit is feet, otherwise meters. The default color range is about 18 inches (0.45 meters) either side
Includes the tide?	Yes

Source: computed by RipIQ from SSH - Altimetry (HYCOM model sea surface height).