SST (L3 Composite)

More detail

The newest frame is about two hours old, so the newest one or two hours on the time slider are empty at first and fill in on their own.

Step back an hour or two and take the hour that was clearest over your spot. The layer covers the Gulf of America, the East Coast and Baja.

It carries the daily warm-up, so an afternoon frame reads warmer than a dawn frame of the same water. It will not match your gauge exactly: a satellite reads the very top of the water, while your gauge reads about three feet down.

How it relates to the other temperature layers. SST (2hr Composite) is the freshest temperature in the app, rebuilt about every five minutes. SST (MUR 1 km) is a daily map with the cloud holes filled in by estimate. SST (ACSPO 2km) is a daily nighttime map that leaves cloud blank. Use this layer for a clean hourly picture, SST (L2) when the extra hour matters, SST (2hr Composite) for the freshest look, and SST (MUR 1 km) for the full picture with no holes. Sea Surface Temperature, from HYCOM (U.S. Navy model), is a forecast, not a measurement. All of them share one color scale. For breaks drawn as lines, use SST (GOES-19) Fronts, which is hourly too. For temperature below the surface, use Water Temperature at Depth.

If the colors look wrong after you change settings, reset the range in Layer Settings. The default is 41.9 °F to 91.4 °F.

The numbers

How often it updates	Every hour, 24 frames a day
How fresh it usually is	About 2 hours after the hour it shows
How detailed it is	The satellite's own sample over the Gulf is about 1.5 nautical miles
Where it covers	Gulf of America, East Coast and Baja
How far back you can look	8 days back, hour by hour
Goes blank under cloud?	Yes, on purpose
Observed or modeled	Observed. Nothing is filled in
What you see on screen	Fahrenheit by default, Celsius if you switch. Afternoon frames run warmer

Source: a satellite picture from the GOES-19 satellite (NOAA).