40/70 Benchmark

Even if a storm cuts in that pattern, a lot of us are still probably getting front enders that will be more fruitful than these clippers that are drier than a nun's no-no given the antecedent airmass.

Considering the length of the 2001 (33 days) and 2018 (20) events, it as 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.

Perhaps these excerpts from my outlook last fall will prove somewhat illuminating.... Lee et al (2019) identified the transition from this Pacific trough regime to the Alaskan ridge regime as most conducive to the type of wave propagation needed to trigger a reflection event, which renders the Pacific trough regime the precursor pattern. This is a remarkable extended forecasting tool given the expectation for a mid January onset of a reflection event, as this implies that the first half of January is likely to be mild and characterized by Pacific trough regime with a rapidly consolidating PV, thus the arctic low regime is also worthy of consideration here during this mid-winter-thaw period. This period will also feature a considerable Pacific jet extension as mild Pacific air infiltrates the vast majority of the CONUS and flooding becomes a concern for areas that amassed a snowpack during the early season arctic high regime. Any seasonably cold air masses are likely to be dislodged from the east coast by a primary storm track across the interior. The expected midseason progression is illustrated in the schematic below that details the typical evolution of reflection event. Note that the pattern begins to reverse in earnest approximately 5 days after the event onset, during which time the anonymously strong PV reverts to normal strength, and begins to stretch due to the building Alaskan and Aleutian ridging that retrogrades from North America. This is why it very mild at the onset of these events, during the antecedent Pacific trough pattern, but by ten days post reflection the pattern has reversed and is characteristic of an Alaskan ridge regime (bottom right above). Once the process terminates and run its course by early February, a more canonical La Nina pattern will likely ensue in the absence of the expected SSW. However, should one materialize as anticipated, another arctic high interval is possible for potential grand finale to the season.

My pre-season idea was for big +TNH to take over second half of January following a mid-month reflection event...this is also a great wave 2 precursor pattern for my forecast PV split in February.

Eh...depends...worked out okay in January 2022 and January-February 2015.

Every time the EURO has a shitty evolution, it's right...never fails. It's seemingly only ever wrong when it's desirsble.

The loss of the big early Jan NAO jives more with my seasonal idea...that said, I'm def. still going to be too warm in January.

Get me a real storm I'll concern myself with thermals.....I'm done with the days of 20s and useless clippers. That's okay if you already have a deep pack...

Yea, I'm ready to risk winter and get on with it.

Yea, I agree with him on late month...just wish we hadn't wasted so much season beforehand.

That's fine, I was just jumping in....

I don't think the rest of winter is doomed or anything....all I meant is it's hard to essentially punt the first half in a cool ENSO year and end up hitting normal totals or above. I will also say that this seasons does have the profile to buck that trend.

There was plenty of whining...yes, I do partake at times, but I also contribute a great deal...not like I just spew garbage endlessly.

I'm done...I vent every now and then, but I'm not carrying on. Just a quick burst this AM.

So you need more evidence to conclude that February and March usually suck in a La Nina??

Nailed my spot...8"

I get that...I think it's wrong. It doesn't have to mean a blizzard...all I am saying is that I'm confident January is +PNA in the mean....maybe it not positioned properly, etc....but it won't be a -PNA month.

Mid January I think that will change...

Right...near the solar min....seasons that average negative NAO in the mean have been declining in frequency, but the time to get them is ascending solar near solar min.

Not you....the sentiment behind the post.

No, actually IMBY, they couldn't.

I still don't think the the seasonal NAO values were as low in the aggregate as they were in past negative NAO decadal cycles.....seasons that actually average negative in the DM mean are pretty sparse and relegated to intervals surrounding the solar min at this point...that said, maybe this year pulls it off.

Yea, def. a very bad sign if we don't get anything major in the next two weeks.

Either Jan 2024 or 2022

What I will say is that I think guidance is underselling the emergence of the PNA...I can see this storm burgeoning back into existence with relatively little lead time when that correction is made.