January 2026 regional war/obs/disco thread

[UnitedWx]

20 minutes ago, powderfreak said:

Flipped to snow and a sporty drive to work this morning… greasy, saw one vehicle in ditch.

 

Nice! My favorite driving conditions... that are lacking around here at the moment

[dryslot]

Been snowing all night into this morning at camp about 3” or so

[40/70 Benchmark]

2 minutes ago, 40/70 Benchmark said:

Looks like my prediction of the mid January Pacific Trough regime acting as a precursor to the ongoing reflection event is a hit.

 

Judah's blog: "And as I have been routinely doing, looking at the wave diagnostics in Figure iv continues to display wave reflection over the weekend and into late January. For both periods shown, wave energy goes up and east over Asia, reflects off the stratospheric PV and then heads down and east over North America where the energy is re-absorbed and could potentially amplify the standing wave over North America and deliver cold air from the Arctic south, east of the Rockies. There is westward wave tilt with height over Asia and an eastward wave tilt with height over North America that is a classic signature of wave reflection. Though the eastward tilt is more pronounced in the first period compared to the second period".

Here is the relevant excerpt from my blog:

Stratospheric Reflection Event Likely During January 2026

Society's understanding of the stratosphere and the role that it plays in modulating our weather is very rudimentary to say the least. The basic conceptualization is that a weak polar polar vortex makes the mid latitudes more prone to cold outbreaks, and while that is true, the method of delivery for cold to North America is multifarious in that it is not relegated to a weak polar vortex/-NAO pattern. In fact, the coldest outbreaks in the CONUS are actually triggered by a strong polar vortex and +NAO regime in what is referred to as a "stratospheric reflection event". During these stratospheric reflection events, heat is transferred upward by a Rosby wave (kink in the jet stream) over Siberia and reflects back downward of off the PV into Canada via the reflective surface posed by negative vertical wind shear in the stratosphere. ( Lee et al 2019). The study notes that these reflection events are most common during the month of January.

 

There is one reflection event on average each season, so they are by no means rar events. Reflective events are declared when the reflection index (RI), which denotes the difference in anomalous poleward eddy heat fluxes in the lower stratosphere between Siberia and Canada, exceeds 1 for 10 or more consecutive days (Lee et al 2019). Reflective events are unique occurrences in that the PV is undisturbed and initially remains strong, before being stretched by the development of Alaskan and Aleutian ridging and returning to normal strength.

 

 

 It is the stretching that delivers the cold south and eastward into the CONUS, as depicted in the "end of event" graphic above. This type of stratospheric phenomenon differs from the SSW events, in which heat propagates upward in waves that converge in the stratosphere, thus weakening the PV by decelerating and even reversing the zonal westerly winds that are ordinarily prevalent in the polar stratosphere. Reflection events also differ from SSW in that they are more favored during the westerly phase of the QBO, with 30/44 events since 1980 having occurred during a +QBO. While this ostensibly renders a such occurrence unlikely this winter given the very strong easterly QBO that is nearing peak, the analog events of January 16, 2001 through February 18, 2001, and January 13, 2018 through February 2, 2018 are being weighted heavily in the seasonal forecast given their strength as general analog seasons due to considerations previously discussed, such as polar, ENSO  and solar considerations. This is also why these two seasons are considered superior SSW analogs. The January 2001-February 2001 reflection event is one of just 9 out of the 44 cases examined in which the reflection window overlapped with a SSW event, which is why there is a heightened risk of this co-occurrence relative to climatology this season. This actually reduces the risk of severe cold, per the study. Here is a list provided by Lee at al (2019) of the most prominent reflection events of the past 45 years, including the primary analogs of 2001 and 2018.

 

 

Courtesy Lee et al 2019

 

The mean length of the process is 20 days, with 10 days being the minimum, and 60 days the maximum, per Lee et al (2019). Considering the length of the 2001 (33 days) and 2018 (20) events, it is expected that a reflection event will begin between approximately January 13th and 16th 2026, and end between about February 2 and 18th. This is consistent with the climatologically favored time frame per the research that was referenced previously.  In order to better understand how the PV interacts with North American weather,  Lee at al identified four distinct weather regimes and listed their respective frequency of occurrence between the months of November and March, from 1979 through 2017, since they last longer than synoptic scale patterns and thus provide an opportunity for longer range prediction. 

Pacific Trough Pattern Precursor for Reflection Events

 Pattern recognition is paramount in the analysis and diagnosis of reflection events because the behavior of the polar vortex has predictive value on each of these regimes at both seasonal, and sub-seasonal leads, which is roughly 15-60 day in advance. "The PV strength significantly affects the occurrence and persistence of each regime and transition between regimes" (Lee at al 2019). Research by Kretschmer et al (2018) illustrated the importance of planetary wave reflection for anomalous cold across North America. This expounded on earlier work by Kordera et al (2016) that found that wave reflection born of Pacific blocking tele-connected to a down stream trough over North America. Thus the implication here is that the Alaskan ridge pattern, which is not at all connected to the PV and is actually accompanied by a +NAO, as alluded to earlier, is most conducive to reflection events and is this correlated to the most severe arctic outbreaks in the US. Lee et al (2019) refers to this type of pattern as the "Alaskan Ridge Regime" , which is similar to the Tropical Hemisphere Pattern (+TNH).

 

 This has been the most common vehicle for cold delivery over the past decade given the increased tendency for +NAO during the winter season, so it is important to remain mindful of the fact that climate change is certainly not prohibitive to severe cold outbreaks. It does, however, decrease residence time due to the enhanced Pacific jet keeping the flow more progressive.

Here is a composite of seasons that fit this +TNH description over the past decade or so.

 

 

Note the similarity to the -EPO predominate extra tropical Pacific pattern that is favored this winter season.

 

 

 

[40/70 Benchmark]

Now the +TNH that results from the reflection event should act as a precursor to the February SSW, just as the Pacific Trough Regime that is just wrapping up was the precursor to the upcoming +TNH interval born of stratospheric reflection.

[40/70 Benchmark]

Hang in there...we aren't going to want for opportunity.

[40/70 Benchmark]

Just now, 40/70 Benchmark said:

Good test for the "La Nina is fading fast" crowd....I call BS on it.....but IF that has any credence what so ever, we won't get boned out of phase 8 residence and amplitude once again. I think we will....watch the models adjust.