2025-2026 ENSO

[snowman19]

5 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 Any stats on this?

[bluewave]

23 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 U.S. Western ridge and colder Eastern trough pattern which will dominate December 1st through the 16th.

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:

[mitchnick]

Updated Euro seasonal out and it can't get out of its own way insisting on AN temps in the east. Don't buy it as mby has been BN for October and November contrary to the Eps seasonal. Heck, even September was only +.5F, also cooler than forecasted. 

https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A AIFS"]%2C"Parameters"%3A[]%2C"Type"%3A[]%2C"Range"%3A["Seasonal"]}

[donsutherland1]

1 hour ago, snowman19 said:

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 Any stats on this?

The sample size is too small for meaningful comparisons. However, 10-20 days after the bottom, there wasn't a clear increase in subtropical moisture during La Niña and borderline La Niña/neutral-cool winters. In a few cases, there was an atmospheric river directed at the West Coast.

[40/70 Benchmark]

1 hour ago, donsutherland1 said:

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:

Tends to in the other direction, as well...that was one of the issues with my work prior to last year...I really neglected the WPO, which is an egregious error because it's very important.

[PhiEaglesfan712]

1 hour ago, mitchnick said:

Updated Euro seasonal out and it can't get out of its own way insisting on AN temps in the east. Don't buy it as mby has been BN for October and November contrary to the Eps seasonal. Heck, even September was only +.5F, also cooler than forecasted. 

https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A AIFS"]%2C"Parameters"%3A[]%2C"Type"%3A[]%2C"Range"%3A["Seasonal"]}

It's called regression to mean. Especially in a warming climate, it's hard to string together several below average temperature months in a row. Do not be surprised if there is a torch in January and February. That's been a staple of -ENSO/deep -IOD years in recent times (see 2016-17 and 2022-23).

[EastonSN+]

20 minutes ago, PhiEaglesfan712 said:

It's called regression to mean. Especially in a warming climate, it's hard to string together several below average temperature months in a row. Do not be surprised if there is a torch in January and February. That's been a staple of -ENSO/deep -IOD years in recent times (see 2016-17 and 2022-23).

1989/1990 season is a good example.

Record cold December followed be record warm January and February (snowy March).

Today some sites are breaking 1989 records.

[GaWx]

3 minutes ago, EastonSN+ said:

1989/1990 season is a good example.

Record cold December followed be record warm January and February (snowy March).

Today some sites are breaking 1989 records.

 I don’t feel 1989-90 is an -ENSO analog to 2025-6. That’s because:

-Dec was slightly +ENSO per RONI (+0.09) and only a hair -ENSO per ONI (-0.01).

-Jan was already a solid +ENSO per RONI (+0.39) and slightly +ENSO per ONI (+0.11).

-Feb was +0.31 to +0.34.

[GaWx]

1 hour ago, PhiEaglesfan712 said:

It's called regression to mean. Especially in a warming climate, it's hard to string together several below average temperature months in a row. Do not be surprised if there is a torch in January and February. That's been a staple of -ENSO/deep -IOD years in recent times (see 2016-17 and 2022-23).

 I still feel that Jan and Feb should be analyzed separately for the NE US. Since 1983-4 as regards -PNA Decs:

-3 times as many -ENSO -PNA Decembers were followed by cold Jans as mild Jans including the recent Jan of 2022. In addition, there were cold Jans in 2014, 2011, 2009, 1985, and 1984. Related to this, 9 of 11 of these Jans were either cold or pretty close to normal.

-But OTOH there were 6 times as many mild Febs vs the only cold Feb (2014).

[BlizzardWx]

The pattern in place is becoming deeply entrenched with the widespread deep snow cover across Canada and the tendency for the PV (or at least a piece of it) to want to sit over Hudson Bay. For a variety of reasons I think the general pattern in place now will want to stick around in some form for a while. I know the EPS weeklies have been insistent on shifting things west late in the month but I have my doubts, and even then the cold doesn't really go south it's mostly just in Canada. I certainly wish we could change some aspect of the pattern because otherwise my area stays dry. For me I need some help from the subtropical jet or for the polar jet to pull in a cutoff low when it breaks south. 

In ninas, I climatologically do better in January and February anyway so I guess we will see.