El Nino Watch

Sea level anomaly boxes

sla_nino34, sla_nino12, sla_west_pacific, sla_south_china_sea, sla_gulf_thailand, sla_samui_coast.

Indices

Daily average satellite sea level in each box: Nino 3.4 (5S-5N, 170W-120W), Nino 1+2 off Peru, the western Pacific warm pool (5S-5N, 130E-160E), the South China Sea, the Gulf of Thailand and the sea just around Koh Samui.

Limits. Near-coast boxes (Samui, Gulf) are noisier: altimeters are less accurate near land.

How to read it

cm above a 1993-2012 mean surface (includes ~8-10 cm of long-term rise). During a strong El Nino the eastern boxes run +20 to +40 cm and the western Pacific near or below zero.

Why it matters for Koh Samui

Sea level rises in the east Pacific before the surface warming peaks, and a high Gulf of Thailand adds to coastal flooding at high tide and in storms.

Sources

ENSO status now

ONI (NOAA CPC)
+1.80 °C, JJA 2026 (previous +1.39 °C)
RONI (NOAA CPC)
+1.36 °C, JJA 2026
Nino 3.4 weekly (NOAA CPC / OISST)
+3.0 °C anomaly, week of 16 Sep 2026 (SST 29.6 °C)