El Nino Watch
The volume of warm water (above 20 C) stored along the equatorial Pacific, measured by the TAO buoy array.
Indices
NOAA PMEL computes each month the volume of water warmer than 20 C above the thermocline between 5N-5S, 120E-80W, for the whole basin and its west (120E-155W) and east (155W-80W) halves, plus the average 0-300 m temperature. Series wwv_anom, wwv_west_anom, wwv_east_anom (units of 10^14 m3), wwv_total, t300_anom, t300_west_anom, t300_east_anom (degC).
Limits. Monthly, based on buoys and ocean analyses; gaps in the TAO array add uncertainty.
Anomaly above 0 = more warm water than normal. Before an El Nino the warm water builds up (recharge); during the event it moves east (east half rises, west half falls) and is then discharged. August 2026: +3.5 x10^14 m3 overall, +4.0 in the east, -0.6 in the west, the classic mature El Nino pattern.
When the warm water volume drops below normal, El Nino is usually ending and a La Nina can follow; for Samui that is the signal that the drought-type risk will fade and a wetter year may follow.