|Last week NOAA announced an El Nino Advisory as onset of El Nino arrived. The Nino SSTA observations do not confirm that analysis. Using the daily NOAA global SSTA observations revealed is that warmth in the eastern half of the equatorial Pacific Ocean is obvious only near the Dateline (Nino4 region). Last week the Nino4 was +0.8C which is certainly above the +0.5C El Nino threshold. However, the daily Nino4 SSTA has cooled to +0.53C so we’re heading in the wrong direction. Last week’s NOAA observations for Nino3 and Nino12 were all beneath the El Nino threshold and the daily observations indicate cooling is occurring. In fact, waters off the northwest coast of South America have cooled to below normal.|
So what is going on here? The second half of 2018 brought an ENSO regime where El Nino was always approaching but never arriving. All climate forecasters agree the problem was the warming eastern equatorial Pacific was not engaging the atmosphere above to produce an El Nino climate. Many climate indices identified this problem including multivariate ENSO index and southern oscillation index. However, in recent weeks the southern oscillation index has developed a strong negative phase which implies the atmosphere is becoming more El Nino-like. The question is whether this SOI trend is in response to an equally robust Madden Julian oscillation signal in the central Pacific or the ENSO regime itself. NOAA believes this is an ENSO regime change,
On the other hand, Bureau of Meteorology/Australia goes with the data…no warm equatorial East Pacific, no El Nino. They maintain an El Nino watch.
Climate Impact Company agrees that an emerging westerly wind burst near the Dateline coupled with warm surface/subsurface water in that region certainly increases the risk of an El Nino onset but probably not until northern hemispheric meteorological spring. Also, keep in mind what we’re seeing now occurred 2 or 3 times in 2018 and El Nino failed to develop. Finally, while the subsurface is warm near and east of the Dateline the subsurface eastern equatorial Pacific has cooled including the northwest coast of South America causing the Nino12 SSTA region to cool to below average the past few days.
There are 2 bottom lines here…ENSO is technically neutral but El Nino risk is certainly there. The El Nino-like tendencies occurring now mostly stem from a Madden Julian oscillation episode. Aside from ENSO and MJO, Climate Impact Company suggests traders/analysts be more aware of regional warm/cool SSTA regions which are causing localized climate regimes. Examples are super warm SSTA east of Australia causing harsh dry and hot conditions which have affected both Australia and New Zealand and warm SSTA off the East Coast of the U.S. which has allowed a high pressure ridge to hang on preventing frigid weather in the western U.S. from shifting into the East U.S.