bluewave

My guess is that all these stratospheric disruptions in recent years are linked to the Kara-Barents Seas warming and loss of sea ice there. Many recent studies how focused on this region. Notice how in most of the recent summers the Pacific side has done better than the Atlantic side. While the Pacific side enjoyed the coldest start to summer in a while this year, there was record breaking warmth with low sea ice on Barents and Kara areas. So we have had quite a run of SSWs and weakened vortices since 2020. The successful SSWs and weaker PV for winter weather fans were in January 2021 and November 2025. These events were able to get the Pacific to back off. Even though it took nearly three months following the November 2025 weak PV in late February for our first KU in four years to finally click. Fast forward to the disruption of the PV in February 2023 and we saw the disappointing result of what such an overpowering Pacific leading to the Baja trough that winter could do. Next up were the twin SSWs in January 2024 and March 2024 during our last weaker super El Niño. But we saw quick snap backs of the PV following those events with the very hostile Pacific continuing. Now this early PV disruption is forecast to have a quick rebound. So it’s quite possible that we see another weakening sometime from January to March. But with such an extreme east based El Niño, it’s an open question how much success it will result in. Since it could very well follow the 2024 quick rebound script. https://www.climate.gov/news-features/understanding-climate/understanding-arctic-polar-vortex How Barents Sea Ice Affects the Stratosphere Heat and Moisture Flux: When sea ice retreats in the Barents-Kara Seas, open water exposes the relatively warm ocean to the atmosphere in autumn and early winter. This releases extra heat and moisture. [1] Planetary Wave Enhancement: The added heat creates local thermal anomalies that alter lower-atmosphere pressure patterns. This change enhances upward-propagating planetary waves (Rossby waves) from the troposphere into the stratosphere. [1, 2] Vortex Disruption: When these energetic waves break in the stratosphere, they deposit momentum and heat, weakening or distorting the high-altitude circumpolar winds known as the stratospheric polar vortex. In extreme cases, this triggers an SSW, where stratospheric temperatures jump tens of degrees in just a few days. [1, 2, 3] https://repository.library.noaa.gov/view/noaa/67133 Major sudden stratospheric warmings (SSWs) occur in the Arctic around six times per decade. During winter 2023/2024, two major SSWs occurred – a relatively rare event, having occurred on average only once per decade. Here, we summarise the evolution of the two SSWs, their dynamics and impacts on stratospheric chemical processing and tropospheric weather patterns. While both SSWs were displacement events, they evolved remarkably differently. The 16 January SSW was short‐lived and did not exert a canonical influence on surface weather. In contrast, the 4 March SSW followed a more typical evolution, albeit with only weak coupling to the troposphere.

I only posted the highest peak departures during each of those months. Numerous surrounding stations were also over +10. So you are correct that it would probably take hours noting every station to reach +10 or more since 2015-2016. It’s anyone’s guess at this point exactly where the highest monthly departures will occur during the winter months this coming season. 2015-2016 was unique that it combined with the MJO 6 getting the greatest absolute temperatures and departures all the way to the East Coast. But the CONUS record for warmest December set in 2015 was already exceeded twice since then with two years coming very close. December 2021 and 2023 actually had more extensive warmth and greater coverage of the high departures than 2015. Most of the time the highest departures during super El Niño events occur from the Upper Plains into the interior Northeast. Top 5 Contiguous Warmest U.S. Average Temperature December December 2023 39.76°F 131 December 2021 39.34°F 130 December 2015 38.64°F 129 December 2024 38.16°F 128 December 2025 37.83°F 127 DEC…2015….NYC….+13.3 MAR…2016…MOT….+10.5 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5 DEC….2024…..LND…..+11.3 DEC….2025….CPR…..+12.1 JAN….2026….RIW……+10.2 FEB…..2026….LND…..+11.3 MAR….2026….PHX…..+12.5

It’s as if these two super El Niño are linked together through some shared underlying mechanism since the Nino 1+2 365 day mean SSTs never dropped below neutral following 2023-2024. The trades also didn’t fully returned to normal north of the equator in the ENSO regions over the same period. Much different than all the previous super El Niño events of the past.

Currently around the 15th warmest fall to date across the region.

In terms of most people who have had much lower early season heating demand with such high energy costs these days it’s a big help to their finances. The average people I speak to off this forum has been very happy with how warm the winters have become since the 2015-2016 super El Niño. So this board is a real minority in terms of the general populace which would rather spend their winters in Florida than the Northern States. Internal migration has been to the sunbelt from the colder climates across the CONUS. But there has been shift to this pattern in the last few years.

Overall much too cool a forecast for the CONUS in October since we are in top 5 warmth territory. Climatologist49 @climatologist49.bsky.social Follow After finishing with the record warmest July, the record warmest August, and the record warmest September, the Contiguous U.S. is on pace to have the 4th warmest October on record. The warmest, 1963, was 4.8F above normal. It's still possible that this October could move higher up the list. 11:30 AM · Oct 23, 2026

Parts of the CONUS are at +8 to +9 and it’s only October. None of the seasonal models were forecasting this from the September runs. Even the early October runs turned out too cool.

The exact CONUS locations of the +10 and greater departures are difficult to forecast until we are into the first week of the month. We have had 17 such months since December 2015 with departures exceeding +10 or greater for some portion of the CONUS. So December 2015 kicking off this new and more frequent CONUS monthly +10 pattern became a trendsetter in terms of this much warmer climate and not an outlier. There is always regional variability involved as to where the highest departures set up. During our last super El Niño in December 2023 it was INL that got the +15.3° departure. DEC…2015….NYC….+13.3 MAR…2016…MOT….+10.5 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5 DEC….2024…..LND…..+11.3 DEC….2025….CPR…..+12.1 JAN….2026….RIW……+10.2 FEB…..2026….LND…..+11.3 MAR….2026….PHX…..+12.5

Last winter was a weak La Niña and the SSW occurred in late November. This early PV disruption is occurring nearly a month earlier before the vortex fully sets in. Plus it’s forecast to rebound pretty quickly. So the amount of potential cold air is going to be fairly limited this early in the season especially against the record Northern Hemisphere temperatures in association with the historic super El Niño. We didn’t have much success with the two SSWs during a much weaker super El Niño in January 2024 and March 2024. Also the weak PV during January 1998 actually enhanced the warmth when the -AO linked up with the Southeast ridge.

You need the Pacific to back off in order for that to happen which is difficult with such an historic east based El Niño.

If you are going warm for December than why are you giving the week 3+ weeklies any credence?

The exact locations of the +10 and greater departures are difficult to forecast until we are into the first week of the month. We have had 17 such months since December 2015 with departures exceeding +10 or greater for some portion of the CONUS. So December 2015 became a trendsetter and not an outlier. DEC…2015….NYC….+13.3 MAR…2016…MOT….+10.5 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5 DEC….2024…..LND…..+11.3 DEC….2025….CPR…..+12.1 JAN….2026….RIW……+10.2 FEB…..2026….LND…..+11.3 MAR….2026….PHX…..+12.5

That’s the classic week 3 to 4 Euro default 500 mb pattern it was running with during November 2015. It didn’t start to see the actual December 2015 pattern until the month already started. For much of the 2023-2024 super El Niño season it was doing the same thing even following the two rare SSW events for a super El Nino in January 2024 and March 2024. https://repository.library.noaa.gov/view/noaa/67133 Description: Major sudden stratospheric warmings (SSWs) occur in the Arctic around six times per decade. During winter 2023/2024, two major SSWs occurred – a relatively rare event, having occurred on average only once per decade. Here, we summarise the evolution of the two SSWs, their dynamics and impacts on stratospheric chemical processing and tropospheric weather patterns. While both SSWs were displacement events, they evolved remarkably differently. The 16 January SSW was short‐lived and did not exert a canonical influence on surface weather. In contrast, the 4 March SSW followed a more typical evolution, albeit with only weak coupling to the troposphere. Forecast Verification

We can say that the pattern the last few weeks has been reversed from the same time period back in 1997. The strongest 500 mb trough and STJ is near the Southwest rather than the Southeast leading to the flooding and severe weather more focused in the Southwest. This is why the CONUS and in particular the Southeast has been so much warmer this October than it was back in 1997. The long range seasonal models from a month ago missed the more Southwest focused heavy rainfall. Same for the EPS weeklies beyond week 1 issued in early October. So we’ll just have to monitor going forward to see if some elements of this early season pattern continue. October 12th to 23rd 2026 500 mb pattern compared to 1997 October seasonal rainfall forecast issued in early September Verification

That’s a near record STJ off the Baja being forecast which will help to amplify the ridge over the Great Lakes and Northeast moving into early November.