WeatherEmperor wrote:Kingarabian wrote:Shell Mound wrote:Above-average easterlies have been and appear to be fairly constant around 120°W through the next seven days, retrograding closer to the DL over time. The key is that the easterlies have been sustained thus far and seem destined to continue through the upcoming week. The weak MJO signal, while shifting toward West Africa (the cutoff between Phases 8/1) over time, certainly isn’t helping WWBs expand east of the DL through this period. (Incidentally, during the same timeframe, the NAO index looks to be quite negative, which, along with the position and amplitude of the MJO, should aid not just continued gradual cooling of NINO 3/3.4, but also additional warming of the MDR.)
In most cases, decent MJO amplitude over phase 8 results in westerly anomalies or very weak trades in the EPAC (typically between 140W-100W). Models are showing weakened trades across the EPAC starting around April 10. In the next 5-7 days there will be a 10Ms WWB just west of the dateline. The atmosphere still has ways to go in switching to La Nina, despite the upwelling @ the subsurface. That's evident through the disruption of enhanced trades and a negative SOI.
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In the Spring of 2017, the Enso models were showing slow warming to El Nino levels but the atmosphere was Nina like and that ultimately caused El Nino to fail. Do you think the opposite can happen this year where the models are showing Nina but the atmosphere is more Nino?
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2017 had to be one of the biggest forecasting failures for climate models. I'm not sure how they missed a combination of strong and persistent trades and a lack of downwelling Kelvin waves.
Late winter and throughout spring 2017, strong trades dominated the entire Pacific. A moderate WWB between January and February 2017 triggered a downwelling Kelvin wave that kept the surface sea temperatures near El Nino threshold until June. But there wasnt much beneath the surface, especially as we got closer to June.
So yeah 2017 had a lot going for it from the atmosphere which aided in the transition into cool neutral and then into a La Nina. So far 2020 has some similarities in that the atmosphere is still leaning a certain way. However during March, there were signs that the atmosphere could be moving towards a cooler ENSO. But the forecast of below average trades or even westerly winds across the Pacific during April by most models can throw a wrench into things.
IMO (note this is not supported by the CPC), It looks like a weak El Nino is/was present when looking at 850mb wind activity since late fall, and the persistent OHC at the subsurface. If that's reality, then a transition into cool neutral and into La Nina make a lot more sense going into ASO. If the reality is that were in warm neutral, then the possibilities remain wide open for ASO.