El Nino Watch
About 50 moored buoys along the equatorial Pacific that measure sea temperature (surface and deep), air temperature and wind in real time.
Ocean
The Tropical Atmosphere Ocean (TAO/TRITON) array is a line of buoys anchored across the equatorial Pacific, run by NOAA and Japan's JAMSTEC. They measure the temperature from the surface down to about 500 m, plus winds and air temperature.
They were built after the 1982-83 El Nino, which was not detected in time. They show Kelvin waves and wind bursts as they happen.
The app shows the surface temperature from buoys with a recent reading, on the Map (green dots) and the Indices page.
Warmer readings in the east than usual = El Nino-like. Buoys go offline for maintenance or damage: a missing buoy is not a signal.