Sudden Southern Oscillation Index Crash to -3.6!

Highlight: Sudden southern oscillation index crash to -3.6.

Discussion: Today’s southern oscillation index (SOI) has descended to -3.602 (Fig. 1) which is an extremely El Nino-like value and triggered by an area of low pressure moving near Tahiti. The last time -SOI spiked to this level was for one day on August 17. The last time a group of days with -SOI occurred was during June of 2020. The sudden reversal to -SOI today is likely due to a weakening east-shifting Madden Julian oscillation episode. The -SOI may last a few days causing the solid moderate-to-strong La Nina signature present now to weaken slightly. The Nino SSTA regions for last week were steady moderate strength La Nina (Fig. 2). Climate Impact Company will issue a new 2022-23 ENSO outlook later this week.

Fig. 1: Monthly southern oscillation index has stayed in the La Nina-like positive phase during the past year. However, the daily SOI lowered to -3.6 today.

Fig. 2: Nino SSTA regions and their observations for the past 12 weeks.