2025-2026 ENSO

[snowman19]

4 hours ago, GaWx said:

Back to 1995-6, lowest SOI plunges -ENSO/lagged NYC wx

-52 on 2/17/17: MB 3/10-18 and 9.7”

-49 on 12/10/12: B 12/26-1/3 and 0.4”

-47 on 12/19/95: MB 1/2-12 and 25”

-47 on 2/2/13: B 2/7-10 and 11.4”

-44 on 12/4/25 (due to strong compact Tahitian low) ??? 


-39 on 12/14/01: 12/30-1/2 MB/0”

-34 on 1/19/17: 2/9-10 B/9.4”

-31 on 11/7/22: 11/14-21 MB/0”

 

 The above tells me that IF there’s possibly any partial correlation of a strong -SOI during -ENSO to cold and/or snow at NYC, it’s not until 1-4 weeks afterward. A period of very heavy snow and/or MB temps occurred 1-4 weeks after 6 of the 7 sub -30 cases. This could easily just be random considering the small sample size and that this is pretty spread out (1-4 weeks afterward).

Several years ago HM did a write up on this. There is a SOI correlation, but it’s during El Niños only. As I’m sure you already know, the STJ is driven by thunderstorms in the tropics and the polar jet is driven by temperature contrasts. Strong -SOI enhances Nino related thunderstorm activity in the tropics and subsequently strengthens the STJ, which is already beefed up by the standing wave El Niño convection on the equator. When there is a big drop in the SOI, the southern stream gets enhanced and the chances for east coast storm activity goes way up afterwards. This does not apply during La Nina’s. Many years ago, JB decided to incorrectly apply and hype big SOI drops to corresponding to STJ/southern stream enhancement, east coast storms and arctic outbreaks during La Nina’s and it was taken to be fact by the weenies and I guess even by some mets….

@donsutherland1

[bluewave]

21 hours ago, Terpeast said:

Trending down, yes, but the thing is AAM forecasts have been biased too negative over the past 30 days. When correcting for that, AAM may be closer to neutral. 

This source shows the strongest tendency decline in months. Makes sense since we are seeing a big reversal from all the +PNA warmth last December which was a mismatch to the La Niña background state.

The more robust La Niña background states can feature strong gradient patterns in December with a cold Canada and Northern Tier. Especially when the pattern matches up so closely with the December MJO 6 composite.

The forcing in the MJO 6 region is driving the Western Ridge and Eastern Trough pattern which will dominate the first half of December.

The stronger blocking near Greenland is a result of the other area of the forcing in the Western Hemisphere and the recent +AAM spike in late November. So a bit of a hybrid composite with the split forcing. 

Split forcing pattern 

 

[donsutherland1]

The EPS and GEFS are indicating that the WPO will spend much of the December 10-20 period at or below -2.000. Regardless of whether the EPO is positive, AO is positive, and PNA is negative, severely negative WPO patterns tend to overwhelm the impact of the other teleconnections. Such patterns typically feature colder than normal conditions in the eastern half of North America and warmer conditions in the western half.

December 15-18, 2013 offers a representative case with the distribution of warm and cold anomalies: