Fig. 1: The subsurface equatorial East Pacific is warming rapidly foreshadowing El Nino ahead if the warming process continues.
Discussion: The subsurface equatorial East Pacific warmed dramatically during March (Fig. 1). The catalyst to the warming was a transient convection phase of the Madden Julian oscillation (MJO) across the tropical Pacific. MJO flipped surface wind into the westerly direction in the deep tropics of Maritime Continent which extended eastward across the Pacific forcing warm subsurface water near and west of the Dateline to extend eastward recently reaching the northwest coast of South America. The warming east of the Dateline is dramatic during the past 7-10 days. Subsurface equatorial temperature trend in the equatorial East Pacific is an excellent diagnostic foreshadowing ENSO phase change ahead. In the scenario of the past 1-2 weeks, La Nina is gone and possibly quick transition toward El Nino is indicated if the subsurface warming continues. The MJO episode flipped southern oscillation index (SOI) to the negative phase indicating the atmosphere is responding to the warming of the tropical East Pacific. The Nino SSTA regions continue to warm (Fig. 2). Many dynamic ENSO phase forecast models indicate a full-throttle El Nino by June or July!
Fig. 2: The 12-week Nino SSTA tracker reveals ENSO has warmed into neutral phase based on the Nino34 SSTA observations.