The subsurface eastern equatorial Pacific continues too steadily warm. A Kelvin Wave moving east across the Dateline during early December reached waters off northwest South America recently while a second Kelvin Wave emerged near and east of the Dateline and is drifting eastward. The atmosphere remains slow to respond as southern oscillation index (SOI) stays positive and 15-day forecasts maintain the positive phase.

GFS indicates a progressive MJO toward the Dateline in the 8-14/11-15-day period. If so, ongoing U.S. warmth continues and could become stronger. Yesterday, NOAA introduced the Relative Operational Nino Index (RONI) which provides a new Nino34 index accounting for the historical general warming of the global tropics. But! Does this new index effectively identify ENSO pattern change and intensity?

Dynamic models indicate that possibility while a constructed analog keeps ENSO in neutral phase. We’re in the ENSO prediction barrier right now, when ENSO forecast skill is low. Close monitoring of ENSO is required during the next few months.

Right now, the leaning-edge of a Kelvin Wave shifting through the eastern equatorial Pacific during the past few weeks has weakened just before reaching the northwest coast of South America. A new Kelvin Wave has strengthened and shifted just east of the Dateline. A westerly wind burst associated with the new Kelvin Wave is present just west of the Dateline.