TUESDAY, 08-SEP-15 / 2:30 PM CDT
A FULL WX UPDATE WILL BE POSTED WEDNESDAY, SEP 9TH
SST ANOMALIES SURGE OVER PAST FEW DAYS 
TO NEAR ‘SUPER EL NIÑO’ CLASSIFICATION After triple checking the TAO Buoy data reports for consistency (especially since the latest CPC Weekly ENSO update did not report any change in the SST anomalies) – I'm fairly certain that SST anomalies in the benchmark Niño 3.4 region have increased by 0.3˚C to +2.4˚C during the past week. Other environmental metrics have also increased slightly – though most have remained unchanged. Nonetheless, I believe it’s fair to say we are arguably close to having a ‘Super El Niño’ Event.
To be clear, SST anomalies during the 1997 ‘Super’ event did briefly peak at +3.0˚C during the fall - but some of the other atmospheric variables did not go as high as they are now. And while the current overall intensity may be close to the peak – there are several reasons that argue in favor of at least some modest, additional intensification:
1) Still very robust low level westerly wind anomalies in the low latitudes in the west-central and central NORPAC
2) Additional evolution/expansion of the 200mb wind anomalies, and the prospect for another MJO later this month (and an accompanying WWB?)
3) Seasonality has always tended to support the peak anomalies in late OCT for the very strong warm events.
But there is one additional caveat to all this: SST values during early fall often vary more than typical as 'normals' increase and daily fluctuations in actual SST’s tend to be larger – but overall, this was a widespread warming and is indicative of a still 'strengthening' event.
All that said - in terms of the upcoming Winter Weather – OTHER developments during the past few weeks may now be more important to monitor – so read on…
THE WARM ‘BLOB’ IN THE GOA AND ‘COLD POOL’ IN THE NORATL Over the past 6 weeks, the very warm SST’s in the GOA that have been in place for over 2 years have slowly been weakening and ‘shifting’ towards the south/southwest. Many forecasters have attributed this ‘warm blob’ as a key reason for the past two very cold winters by forcing a strongly positive PNA (which teleconnects with cold weather in the southeastern 1/3 of the nation).
I had ‘forecast’ this weakening of the GOA warm anomalies earlier in the summer because research has shown that cooler than normal SST’s in the far western Equatorial Pacific tends to ‘lead’ cooling in the GOA. And this is well on its way to verifying. If the trend continues – then the impact of El Niño is likely to be THE primary player in the upcoming winter pattern.
Fig 1: SST anomalies in the ENSO regions primarily based on Buoy Data It is clear from the above that SSTA’s in the critical Niño 3.4 region have warmed substantially over the past week – up by 0.3˚C as the +2.0˚ isopleth now extends across the ENTIRE 3.4 region. In the eastern portion of the Nino 3.4 region, the previous MAX readings were around +2.5˚C, encompassing about 25% of the 3.4 region. Right now, the +2.5˚C isopleth encompasses about 40% of the region, but +3.0˚ readings now cover another 10-15% of the region. At the same time, the cold water at depth in the WPAC has also intensified, but has not shifted eastward to any significant extent yet. Usually, the eastward trend begins when El Niño has ‘peaked’.
Fig 2: SST Anomalies in the NORPAC and Atlantic region Compiled using both buoy AND satellite derived SST’s, show even stronger positive readings across the ENSO regions – along with ‘cooling’ in the GOA and ‘warming’ in far northern ATL. The +2˚C isopleth extends further west beyond the 3.4 region – and +3.0˚ readings were analyzed over 10% of the 3.4 region in the east. Several +3.5˚ areas are noted east of the 3.4 region – with spot values over +4.0˚!
Fig 3: MJO ANALYSIS and Forecast from 3 Major Global Models The MJO itself remains weak and incoherent – basically unchanged for the last 6 weeks. However, as alluded to last week, almost all of the major model ensembles have now begun to hint at an increase in the MJO signal – primarily in the far western Pacific near the Philippines and Indonesia later this month. Depending on how this develops (let alone, IF it develops at all) – it raises the possibility of a significant Westerly Wind Burst in OCT, or at least a strengthening of westerly anomalies. Of course, there is also the possibility that it could create an enhanced easterly wind anomaly ahead of the signal which would weaken the SST anomalies. However, considering the strong El Niño ‘base state’, weakening from an MJO at this stage of El Niño's evolution seems unlikely.
✭ The Next Regular WX Update will be posted tomorrow (WEDNESDAY, SEP 9) ✭
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Steve
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