Typhoon Tip

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.

Well anyway… It was a fun system here where I am located so no complaints from me Four inches of blue ...got a little threatening there for a little bit around 2 o’clock when it started to get lower visibility and the trees started to sag a bit ... oops, so it cut off early - like I said if you’re a winter enthusiast just be happy it’s not March 15

Okay - I guess I missed something ? anywho for winter enthusiast .. at least this isn’t happening on March 15

Yeah it’s like we’re still in the wrapper around the CCB but I think it’s getting eviscerated by downsloping other land source drying when deeper lift passed away ...other mechanics to consider. But in the past these 320 to 350 direction winds here kill CCB wraparound

Im thinking the last half of this system pretty much just didn’t happen? Certainly happened well shy of those late guidance last night ...they had moderate to heavy snow deep into the evening… interesting. So we were done here by 4:30 or 5 o’clock this evening and we’ve had nothing but mist flurries and drizzle temperatures rising back to 34 ever since. I think I am kind of kicking myself for something I noticed yesterday. And it seems to be playing out here until I get a better explanation... I would say the last 1/3 of QPF from last night’s NAM over Eastern sections was thru a 320° wind. I’ve noticed over the years that the NAM tends to hold onto substantial precipitation way too long when wind backs to the northwest around coastal events. Rad is filled with what looks like probably chaff/virga now. I’ve seen this before it’s like the models think this is heavy D form banding

probably takes some philosophical perspective ...which won't really be fun until 10 years have past .. but, if this had more cold, it may not have even happened... It's not physically impossible that it may have caused the storm to behave differently altogether... like the baroclinic zone might have been displaced 100 mi S and E by a weightier cold, and then the low evolves on the right entrance aspects of the trough and then goes on up and hits D.E.M. ... I mean, we think of these things in terms of "if this had been cold enough" ... and I'm not sure it really works that way.. If we had a steeper colder air mass with this same mid troposphere trajectories, I'm not sure the low develops and so easily jumps to the inside of the wind max axis - this dynamic core in interior mass with light rain in the Berk's speaks volumes in atmospheric dart throwing -

Jesus Christ... y'all are straight up neurotic ... at first hint, how dare it snow less ! lol - I'm sorry... Fill out our comment cards on the way out - 'the french fries were soggy and the waitress was a bitch'

I lived down Washington street toward Winchester Center for a couple of years in the early 2000s... that snow you get there is like showing up at the party after most have left and there's still one or two cold lobster tails left and some chips.. but the gig's over.. Finally, we'd flip... but then it ended.. I don't think that's this time. You'll probably do pretty good there this evening but ...just reading your post reminded me of those exit left-overs -

Confirmed... Met friend down in Auburn said the trees are shedding their snow in massive splats during the last hour of more S- like fall rates. he's 33 stuck like me here... Something like that happened here - ...we seemed to accumulate more proficiently at 35 when we first committed to snow type... hit 2 " in that first 1.5 hours-worth. Then...it snowed like hell for 2 hours ? 2.5" like where did it go ? We are now 3" I am noticing some small icicles formulating at drip sites ...because I am a catastrophic dweeb and look for shit like that.. lol. but it's glooming and cold and darkening so .. can't see this going up. May also be some pancaking with that 7:1 ness

Hi def vis loop looks like a down burst near the Canal area over Cape... I wonder there's some weak 'folding' going on

Funny...I was thinking that exact same thing an hour ago - really simple cookie-cutter reasoning kind of was sufficient, 'if it falls faster than it melts, it snows' lol.. .but yeah -

it's not unprecedented for the outer Cape/ or Islands to clear in these coastal storms. The 700 mb passing ideally for the HFD-CON axis, typically/geometrically favors a dry intrusion to that latitude out there... What'll happen soon is that the low will migrate up toward Boston Light over the outer Harbor, and down there they'll get pounded by a rapidly backed west gale/storm force iso. b wind pulse and probably storm chaff ripped around the backside -

Honestly ... ? I started sensing a bit of 'event fatigue' as early as yesterday morning... I figured seeing the actual routine unfold might tune me back in, and it did... admittedly. I was pretty excited to watch the transition this morning. I think we almost have too much access to data this and modeling that... and constant stimuli therein and from and it's a constant siege and just when we could deflate the next model cycles is out ... There's no 'real' down time ? Not like even 10 years ago when the product suites worth a shit were really just the 12 and 00 cycles.. Now, seems you can't take it all in and you have to leave some behind ... then this engagement or other social media? Jesus - 'nough is 'nough. It does in a way put me off to it. I don't see this storm as warranting that sort of attention. This is a typical "seasonal anomaly" - nothing extraordinary... and probably worth some dialogue and fun with the models.. but I probably could have imposed more discipline on my own weather obsession - We'll see where the late afternoon takes us... Seeing 'back edge' rad behavior into SW CT and a pan-wide weakening out toward Orange - may be consolidating this into a stricter central/E deal as we speak. I'm wondering if we'll get some rad pulsation/flairs in bands in said region. Also, where's that slow down the late runs had last night, too - wondering about that but ..heh, I don't wanna even look at a model lol 3" of glob... S... 32.7

This may seem silly and it is admittedly/anecdotal .. but, my wind and ceiling swath are both NE proper here over Ayer and my experience with CCB headed coastals in this region, ...we're usually good for a late rad arc/flaring until the wind really backs 360 or 350 ... That said ... I think Will nailed it that we're missing that crucial tick or two from this ranking more memorably ...It's the right format otherwise -

Our temp fall slammed shut about 1.5 hours back here in Ayer ... Fell from 40 to 32 and change but has been 'frozen' at that 32.5 .. . We have no icicles off any metallic objects and water is dripping - it's seems we are accumulating at nearly the melt rate and have been for the past hour, as vis has been 1/3 or so the whole way and we have 2.25 unchanged. Maybe a dynamic butt kick to plumb that 31.5 clincher but for now..we await that meso band -

Just gazing at Will's rad posts... ... not hard to imagine this thing as really being a rather progressive system this hour - moving right along. Deep? mm .. yeeeeah, but middling so - I mean, considering we've seen some 965ies passing abeam of ACK more than a couple times over the past 5 years... 980 isn't really memorable. But who am I kidding - we dorks remember flurries.. Some of the late guidance runs last night were sort of hinting at a slowdown interval ... I'm wondering if that still transpires ? It'd probably be mid evening ... we see the system hesitating on some of these same products/sat...and maybe the arc CCB 'stinger' and so forth lingers on a bit... 32.4 S ... some swaying in the trees but no timbre cracks yet. 2.25"

Your avatar's name is 'driveways' huh -

You might do well pretty quick.. . That's what happened here - we silver-slush to whitened everything exposed at the same time. Interesting... wasn't differentiating at all between tree, road, car... grass. It all seemed willing to glow and then just be white. 33 F here over an inch... The sound of civility is muting ...atoning to the damping nature of snow filled air. The white noise of humanity is snuffed(ing) rending the only thing audible are those damn beeps of DPW vehicles in reverse... That's how we know we've really crossed the threshold into an actual snow storm as opposed to whatever that was this morning - that "muting" effect. Its getting quiet out there... Trees starting to sway a bit.

1.25" accumulation here in Ayer, Ma 33 F ... Underscoring the point... This is in a valley? It is - ...it is interesting that in this area, we are not really depending upon elevation. Everyone/where else seems to be seeing that but I am not. I drove up to Groton center and across the NE side of town, just over the Littleton line and back into Ayer and home and this whole region was committed to snow as of 1.5 hours ago

No need to do that ... ...go to you car. Enter said vehicle. Observe particle impact behavior upon windows/windshield... If the 'blatting' pattern ends up in 'star' structures - your transition level is probably not that high up and you are close... Rain drops in that phase of early transition will catch your attention as they zip by ...sort of 'glowing' a little bit but ... they may also not be falling quite at the same terminal velocity of straight liquid particulates...

The complexion of this down here even in the valley is starting to look that way, Will - it's interesting ... elevation doesn't "seem" as important as the dynamics for this ... I mean the top-down cooling part of this seems to completed for our region of NE/N Middlesex Co