Typhoon Tip

Okay yeah... agree with Scott .. It is unlikely that results that way - I mean it can...sure. But the model is probably transitioning, needing multiple cycles to land on another isothermal headache snow column... Probably just early on in that process with this run. One thing ...I thought about this morning, and wonder if we're seeing some staggering? It is not uncommon in multi- Pac ejection/ progressive patterns, the leading disturbances end up becoming more dominant. - this thing over the 5th/6th did that. It was originally going to be the 7th and 8th, and I did post earlier in this thread that we should watch the 5th system 'in the foreground' because it had ensemble coherence/weighting therein... So what happens, ... it disappears for a couple cycles and then comes back and eats the pattern's lunch! the 5/6th became synoptically dominant. It may be that a Tuesday system gets to be a real threat. Hard to know - again again again this anomalously fast progressive business is not a good fit for model accuracy. Beside, if we can get in get off get out on Tuesday ... we have a shot for the D9 to be less interfered -

I haven't even looked at it yet ...

Lol... ho man, you'd get a kick outta the JMA. ...that sucker looks like 2.78" of accreted ice, then, 24" of snow on top - from overnight Saturday night through next Tuesday ... fuggin cryo-apocalypse. I mean, I posted two days ago that this pattern was only deceptively bad but I didn't exactly have ending the world in mind. lord Is the JMA like ...useful ? I really haven't ever bothered to look.

Yeah ..that's a pretty striking already - thing is ... if/when any polar air bends around the corner it's game over for warm intrusion NE of NYC without some sort of unusually powerful S anomalous firehose .. that's precariously close there -

Short answer: Not impossible ... but low probability - We've obviously experienced some significant errors in handling these flat flows where open Pac waves with strong wind maxes get forced S of the Canadian lower hgts - yesterday I referred to this as 'inverse blocking' ... Whatever works, the PV or general lower heights N have a flow around the bottom ( polar jet) that prevents turning N without phasing... and the the flow is too fast to allow that... so, we end up forcing/correcting the angle of polarward turn S given time. Is this one of those ? That sort of error was more common in the mid 1990s through early 2000s... In fact, 2008 as others referenced... Don't know about recently however. Given to modeling "upgrades" ... Euro's had two and the GFS three since 2010 I think, in a time span where I don't even recall a -AO/neutral PNAP frenzy type patter. In other words, this sort of scenario may not really be tested in recent winter to be blunt. We'll have to see... If it were not for the -AO with the arguable -NAO both in play, it'd be a different discussion entirely -

Definitely watch D9's space - More so than the average ... GEF individual members carrying coherent signal into 80 - 70 longitudes ... with typical spread as to geography for this range - they all have something. That in itself is sufficient at this range to warrant - And as you/we've been noting - ongoing -AO probably not being assessed entirely correctly as to how it influences ...particularly when on-going PNA's neutral - the latter conceptually sprays buckshot Pac waves capable of getting things done, while gambling on polar boundary placements out ahead. One other things folks, - be advised that the pattern we are being handed by the blends and individual runs is an anomalously progressive one. "Accuracy" in timing and placement becomes premium... It's an interesting philosophical quandary of sorts...because - to me - we are above normal confidence in systems of interest, while simultaneously below the threshold of confidence in visualizing what those will entail.. I tend to agree with Will that an icer/mixier look for C-NNE is on the table of the weekend... But again, the D9 is red flagged and has been showing up in the EPS and GEFs with unusual coherence ... Could be a PD-model ordeal in that time span -

I'll probably be glazing eyes over with too much verbosity as usual at some point during the next while here.... but in short, that's an ice-storm pattern big time there. - the rip/read with pearled troughs enhancing periodic confluence with that N stream confluent into a split rejoin along 40 N Lake/NE axis is basically building/science 101 in how to lay a foundation for ice-storm palaces. But, that's the snap shot rip read. It's not taking into consideration how the pattern is or isn't in process of modulating toward some other destination, either...

Here's a whack notion ... ...that D5/6 Euro solution pancakes and gets a colder solution into NY-CNE ... The ejection out the Rockies could be overly amped there? It's a typical albeit nuanced bias of the Euro around that temporal boundary ( that separates the outer near term to the mid range... ) It wouldn't take a hugely flatter solution to limit the erosion ... Low probability but either way, that trough looks too deep on D5 to me. If it is manufacturing ... it ends up conserved up the St Lawr out in time....

I actually outright like that look ... has a bit of a nickel-dime suggestion to it .. can envision the steady diet of 2.5 to 3 day advisory packaging ...

gah-hod ... oy you're brutal -

Great find ! ... I was thinking about that 'front end loader' type pattern and this just nails the example right down - boom... In this/that paradigm ( this may end up that way in other words ) the lower heights and/or vortex up there in Canada becomes like an ' inverse block' ? Basically ( not lecturing you per se - you now this...) we think of blocking as ridge nodes wobbling around along the 70th parallel, directing stuff around them - which ..is a miss-read anyway.. the ridge is there because of the stuff going around that region, not the other way around... - Anyway, different discussion... But in the case of vortexes and depressed heights and suppressed jets, the block is expressed via suppression ...such that deeper mid ranged and/or extended events will have to correct S ...usually they do so by stretching also..such that you can get a pancaked event with a front load IB/WAA snow blitz ... ( love those 5.5 hours traffic snarl grid lock ) ... or, they shear into pearled lows... And, this whole bag can be icing, too... It's a way to think of blocking in the other terms/directions.. The -AO .. provided a reasonable stable planetary distribution...does support more south position of the N/stream ... SO ...the takeaway is that we are discussing what I like to call "correction vectoring" ...it's exactly what that means in simpler terms - which way is this likely to correct. Unfortunately for my street cred risks ... in the bun direction.

I know ... to the less experienced they think that's a raging E wind everywhere - noooo way man ... that's a magnificent burier jet sig there...talking 35 kt N, 900 mb ... - 6 C dp cryo hose funneling east of the cordillera ... I mean, not saying it's happenin' or nothin' ...but it's still fun as a pass-time to surmise based upon these "conductors" of imagination's symphony -

See ...I don't think the pattern's as bad as merely 'not having a big deal to gawk cinema over' - ... just speaking in general here - I mean, just utilizing the GEFs index as a guide may come with it's own limitations and risks therein ...but, the PNA is neutral - not demonstratively negative in the individual members, or in the very tightly concerted curve at CPC as I'm sure folks can see for themselves.. - not a novel observation pointing that out..But, since we've had spent 10 days robustly positive prior to the neutrality of the curve...and it doesn't actually go neggie, that's like Newtonian there in that objects in motion will stay in said motion until acted upon by a force sufficient to change their trajectory - The PNA --> relay into N/A may sort of vestigial maintain some of the trafficking ... and I think some of these weird solutions are trying to hint that way - ... I love synergistic emergence - it's my new obsession. Hahha... I know I know... But, with the AO tending to remain negative and the NAO ... well, I think that part of its' overrated for now anywho ... It's not a bad appeal from an teleconnector stand point to eb -AO with a neutral PNA driven PNAP underneath... Ice storms have began that way for one.. We could end up split flow ..? Hey - which can be MARvelous overproducing patterns for a myriad of reason...etc... It's not all doom - not that anyone thinks so.. Just sayn'

hahaha - ...perfect, 'nough said Yeah, I'm not insinuated ( ...at least I hope - ) that down sloping at a synoptic scale was the whole dagger... This was like Cesar on March 15, where - like you hint .. - every douche in the room took turns with the knife. lol. I dunno...radar flushed to light and inspite of attenuating beams and so forth... we went light... like, physically, right then... where the rad flushed light - Fit did... Bed did... Lunenberg did. Auburn did...I know folks in these areas, and they all were texting me, 'where's the storm?' I'm like oh god - Frankly? I'm just glad this isn't March 15 and they're going, 'where's winter'

This GGEM solution might be a hoot if/when all that cold loading up in Ontario ... ...uh, if it were not D9, just sayn'

The 12z GFS shows some of the headaches with progressive correction handling - I mean, I've noticed that intense open wave, where "punching" is most apropos through the OV at 132 or so hours, has been speeding up in placement. TT's nice "Previous" option ...clicking backward demos this ..at least 4 clicks worth - didn't bother going back more than that as it's squarely too far into bun-time ranges .... But, the GFS is speeding that up without actually gaining latitude - it's like it's adjusting the x-coordinate ( crucially perhaps ) toward the last decade persistent raging hard-on hemispheric velocity and really should be stretching the flow in lieu of winding things up. It may not mean much ..it may mean everything ..but, a flatter system doesn't erode cold as readily, and as others have noted, the -AO anchored cold in Canada seems resistant to change heading into the late mid/extended range. Heh...not impossible -

Marginality ftl ... ugh. It's almost like it was "marginal + .5" Like, you know ... you can have "marginal -1" or "marginal +1" ? Some situations will look marginal and it's excruciatingly tedious if not all but impossible to really differentiated one 'marginal' appeal from another, but the "synergistic" tendency - which do to being emergence-dependent ...doesn't exist until it does, so cannot really be pre-assessed in that sense - will be warmer -vs- cooler. I've seen marginal situations go either direction, usually, unexpectedly. Maybe the "-1" and "+1" in the sketch numbers above are the synergistic tendencies - nice... solid sci-fi material right there. But hey - It does ( I'm being a little hypothetical on this particular turn of thought ) seem that we are in an era now where marginal flop direction tendency tries to find the +1s. It's "flop direction" ... I sort of snarked in half seriousness about this as being one of those 'intangible gems' about changing climate ...

Oh yeah yeah yeah... Right - I noticed this too out here. There were other aspects going on in the whole of this thing's dizzying array of 'I wish we could have that week of our lives back' - lol.. No but I noticed between 2:30 ( ~ ) and 4:30 pm, we had moderate snow here ... and the stack depth never changed from 3" ... That's all a different discussion aspect for me though - My thing is really why the sudden dwindling took place - Chris hints that the wind going N somehow attenuated the radar and he may and likely is right - it's his technology. Hahah... However, whether the rad was disrupted or not... we definitely had nothing more than street lamp sparking wet flurry mist from 4: 30 /5 o'clock out my way, right when rad did that. Maybe it was just bad luck timing that the rad decides to hide and seek that way. Nice - fits this piece of shit's luck curve anyway .. In the end, we didn't get snowed on as much... As far as that goes, yeah, it's probably both, like you say - ...some shadowing, and a lot of wasted life following this asshole storm

See ...to me this doesn't really refute the shadowing tendency - that example. That's easily explained to me as being proximity -related, where ( literally ...geometrically ) LWM is still closer to the 700 mb core and was not getting 'd-sloped' just yet?

Not sure I understand this... the 5/6 pm attenuation of radar ( I just provided ) was not in the afternoon ? My idea here is that a critical backing/timing therein ...around that 5 to 6 pm time frame, coincided with a rad attenuation as well as a ground truth abatement/weakening of the event - and trying to figure out exactly why. Now, the shadowing and downsloping is a geophysical truism -. Regional air motion going from elevation to lower elevation, pulls the atmosphere down and offsets UVM, but also ..compressional drying do to PV=NRT of the entire mass... The total phenomenon causes what is referred to as 'rain shadowing' ... When this thing closed off at all those levels and the flow was paralleling ( more so than less...) through the deeper troposphere to surface, ...I think it's bit too cutely coinciding with rad/ground truth to not implicate the models as yet again, over doing that back shit. I like that fraud thing ..funny... Yeah, I remember Bruce was big on that back-lash.

Maybe up your way ...? Down here, radar around 5 or 6 pm flashed less and began shredding all over SE VT/ S NH and N Mass... ahead of guidance frankly. I recall some theory being floated regarding signal source attenuation but... mm, I was here, in that area, and what was happening out of doors precisely matched that attenuation - I'd even argue that some of the 'green' banding there was also being undercut/theft a bit, too when the llvs probably (subgeostrophic argument) was backed even more.. Obviously you have ample access to elucidate this shit already but ... here, run this: you can see precisely when this abatement phenomenon swept through and it was real. I was here and observed flurries and mist immediately take over, while this radar was transmitting: https://weather.rap.ucar.edu/radar/displayRad.php?icao=KBOX&prod=bref1&bkgr=gray&endDate=20201205&endTime=23&duration=4 The only thing I can see that really offers that kind of quick larger scale physical forcing was that if we look at the deep layer, the winds backed at all levels - I could be off on that timing...admittedly...but it appeared to be the case. I don't know - fuggit... I'm done

Depends what you mean: are you talking about "snow" - or - the precipitation distribution and output from the storm in general? I'm considering the latter. Altho, I argue that if fall rates did not weaken it would have continued to snow more - so.. it may also be hard to separate the two. It is not just a compressional drying question. It's also a fluid mechanics issue. If/when the wind backed at all levels, 500 clear to the surface such that it is coming down from BTV/RUT VT... That stretches the column and offsets the UVM by "pulling" downward... that's a geophysically clad -. No argument that the lift abated - trying to get to why. So the shredding radar, and lack of ground truth/ in bucket. I'm just trying to figure out why the NAM and even the global models had 4 to 6 additional hours of wrap-around deep QPF that failed to realize from the night before. HRRR seemed to pick up on that Saturday morning ...agreed with the previous poster. interesting.. I've noticed this since first becoming privy to weather modeling back in the 1990s ... that routinely, when the wind backs NW... models tend to hold onto QPF too long ... This smacks enough to bloody a nose as having some of that modeling tendency with this thing. I think it is nice explanation frankly... Deep layer structure create a parallel flow that down slopes ... offsets the backside CCB and that is why the rad shredded and ground truth dwindled from NW to SE prematurely over the course of the evening, and because the fall rates were being stemmed ..that stopped a marginal situation from snowing as prolifically... Either way, the fall rates were not there... I don't think LWM is much refutation on that, because that area was not part of the initial back wind field in the deep layer and can be explained by proximity to the closing surface aloft easily enough -

Yeah that does appear to indicate a 21 to 22z abatement of UVM, sure. The deeper analysis or understanding of the HRRR's parameterization/physical make-up may reveal exactly "why" it showed that. It could be both synoptics and oreographical reasons combined. It's interesting that the timing there coincides with the backing wind. I'm not sure the HRRR has discrete surface topographic/oreographic BL parameterizations - which is interesting if it does. I mean it could be ending lift from synoptics for other reasons. Then, if/when having the backing wind at all levels, from 500 to the sfc would only mitigate the event further. The problem in assessing 'what when wrong' is that the downslope factor cannot be precluded. Rain shadowing is a very real. It is a physically reproducible, empirically observable phenomenon that does dictate regional fall biases and ...this isn't open to Trumpian alternative fact notions of reality... the wind backing from 500 to the surface to roughly a 330 deg direct DID play a part. sorry - not debatable. It's a matter of how much - I did not admittedly look at the HRRR model and frankly ...don't that often? Nothing against the HRRR - that's not why... If you must know I grow increasingly disenchanted at a world mired down - the unimaginable speed of transmission and computing power slowed by clogged tedium of penny-profit schemes... People need to feel pain and anguish to the tolerance of man again - learn some humility and virtuosity ... Instead of trying extort breaths for money. It's embarrassing really... I find myself equally mired down by wishing on cancer diagnosis ... It's no way to live.. eh hm... So, I avoid the effort and rely on increasingly granular products that no one cares about - until petty greed attempts to capture mere pennies there too ...at which point I'll do the world a favor and just stop being involved altogether - lol. ...not being entirely serious here ...

I looked at the modeled contouring at the traditional sigma levels ... the 850, 700 and 500 mb lvls these cyclonic components collocated upon the same axis at nearly the same time and when that happened the wind backed NNW ... right around 21z 1/2 hr later the winds at the surface here, NW of I495, went 350 and flurry mist mixture became the primary fall rate and type. Basically ... our wind shift coincided with vertical stacking and storm loss. I have seen this too often in the past and that wind backing tandem. yeah ... we lost DGZ because the coupled atmosphere stretches when the flow down slopes ... compensating for synoptic UVM forcing. I feel pretty confident you’ll see this in reanalysis. All that then added to physics of descending motion adding evaporation I think together worked against and is why the back 1/3 to 2/5ths of the event fell apart. I also like the idea of ‘melt momentum’ and tall column distance. Didn’t help. As always the case theres probably a cocktail of reasons

Going from an under performance into a zonal/progressive appeal that'll likely average abv normal as the base-line... probably is a wrong rub for many in here. lol.. not rubbing it in; it is what it is. But, my experience is that these sort of modeled looks don't last - they tend to precede an emergence one way or the other. Intuitively that makes sense..The atmosphere is more proficient when if forms pattern - and this thing agreed upon by the bevy of operationals... being non-committal suggestive of like -PNAP/+PNAP in oscillation ... doesn't represent that. I think with the AO trying to average neg ...and the PNA arguably edging positive ... it "could" be a reload black-out period where patience is required. That's the only 'objective optimism' ..otherwise, on the complexion surface it's not fun, no - ... not going to candy coat that. But again...it's not a stable look - that's a morality victory.