The average tropical Pacific sea surface temperature anomaly (SSTA) in the NINO3.4 region (5N-5S, 170W-120W) is often used as an El Nino index.
The figure shows our latest forecast using a neural network model trained with data up to June 1998. The four panels are for 3-, 6-, 9-month and 12-month leadtimes respectively. The black line is the observed SSTA (in degree Celsius), and the blue circles are forecasts.
Forecasts of all 4 leadtimes indicate that the tropical system is evolving to a cold phase (a La Nina event), which should peak around winter 1998-99. We have been calling for a 1998-1999 La Nina since December 1997.
El Nino and La Nina effects on Canada.