El Nino Watch
The temperature difference between the western and eastern tropical Indian Ocean; positive values usually mean a drier season around Thailand and Indonesia.
Indices
The Dipole Mode Index (DMI) is the sea surface temperature anomaly of the west pole (10N-10S, 50E-70E) minus the east pole (0-10S, 90E-110E), monthly, from the Japan Meteorological Agency (1991-2020 base). Series dmi_jma_anom, with iod_west_jma_anom and iod_east_jma_anom for the two poles (degC).
Limits. Monthly values, published about 2 weeks after the month. JMA's analysis can differ by a few tenths from NOAA's or BoM's DMI.
Above about +0.4 C for several months = positive IOD; below -0.4 C = negative IOD; in between = neutral. Positive IOD events usually peak in Sep-Nov and fade by December.
Southern Thailand and the Maritime Continent get less rain during a positive IOD, and a positive IOD during El Nino adds to the drying. It also changes the haze risk from Sumatra and Borneo fires.