December 5-6, 2020 Storm Observations and Nowcast

[40/70 Benchmark]

9 minutes ago, Damage In Tolland said:

Oh it sure will on Sunday 

Obviously...I just mean that it will melt slowly relative to your average 2" snow pack.

[Typhoon Tip]

2 hours ago, STILL N OF PIKE said:

Thank you 

that was 8am sat HRRR, the model WDRAG said to monitor for now cast

does that not show max lift in DGZ leaving at 20z (4pm) and lift in general going bye bye by 5-530pm (above DGZ) ..isn’t that a big old red flag for a 495 Given what we needed to see 

maybe I’m wrong since this was posted as a reason for a crushing by someone but I’m not confident in reading that but that is my intuition interpretation 

How would that chart be interpreted as a crushing for 5-9pm as was forecast 

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 ...

[ORH_wxman]

I think the lift location is more important than “shadowing” which implies a drying out of the atmosphere. 

The precipitation was pretty prolific still looking at LWM on the upper 495 belt pretty quickly. I see hourly bucket tips of 0.16, 0.18, 0.12 after 5pm. 

That is heavy stuff. They just couldn’t accumulate it. It was white rain. 

[40/70 Benchmark]

9 minutes ago, ORH_wxman said:

I think the lift location is more important than “shadowing” which implies a drying out of the atmosphere. 

The precipitation was pretty prolific still looking at LWM on the upper 495 belt pretty quickly. I see hourly bucket tips of 0.16, 0.18, 0.12 after 5pm. 

That is heavy stuff. They just couldn’t accumulate it. It was white rain. 

Yea, my take is that the lift being JUST below the SGZ was fatal given how marginal the low level thermal envt. was.....we needed optimal dendrite production in order to offset that and we did not get it. The heavy fall rates in and of themselves were not enough...we also needed perfect growth.

[Typhoon Tip]

31 minutes ago, ORH_wxman said:

I think the lift location is more important than “shadowing” which implies a drying out of the atmosphere. 

The precipitation was pretty prolific still looking at LWM on the upper 495 belt pretty quickly. I see hourly bucket tips of 0.16, 0.18, 0.12 after 5pm. 

That is heavy stuff. They just couldn’t accumulate it. It was white rain. 

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 -

 

 

[OceanStWx]

17 minutes ago, 40/70 Benchmark said:

Yea, my take is that the lift being JUST below the SGZ was fatal given how marginal the low level thermal envt. was.....we needed optimal dendrite production in order to offset that and we did not get it. The heavy fall rates in and of themselves were not enough...we also needed perfect growth.

Right. Kind of had a partial pupu platter and could never complete the order. 

We had rates, but not the dendrites or low level cold. A little low level cold (elevation) went a long way in this event to help save things. Valleys needed one or the other (dendrites) to come through and neither did. 

[Typhoon Tip]

14 minutes ago, OceanStWx said:

Right. Kind of had a partial pupu platter and could never complete the order. 

We had rates, but not the dendrites or low level cold. A little low level cold (elevation) went a long way in this event to help save things. Valleys needed one or the other (dendrites) to come through and neither did. 

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  

 

[40/70 Benchmark]

16 minutes ago, Typhoon Tip said:

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 -

 

 

Yes....hence the "backlash" member of the fraud five. Bruce Showegler never did manage to wrap his mind around this over the course of a very esteemed 33 year career as an OCM.

[40/70 Benchmark]

2 minutes ago, Typhoon Tip said:

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  

 

It was both.....sure, precip cutoff early in the evening, but it had been accumulating like shit all afternoon, despite heavy fall rates.

[OceanStWx]

6 minutes ago, Typhoon Tip said:

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  

There was definitely beam attenuation going on with BOX. Winds were starting to turn west of north (which is why the dome was attenuated in that direction), so the storm was going to begin to wind down. Like Will mentioned though LWM still had 0.34" between the hours of 5 and 7, so it's not like it was spitting out. It just was shitty snowflakes and a shitty environment to keep them frozen for very long.

[Typhoon Tip]

Just now, 40/70 Benchmark said:

It was both.....sure, precip cutoff early in the evening, but it had been accumulating like shit all afternoon, despite heavy fall rates.

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. 

 

[40/70 Benchmark]

Just now, Typhoon Tip said:

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. 

 

Exactly my point....even before the precip abated, I was not accumulating efficiently.

[40/70 Benchmark]

4 minutes ago, OceanStWx said:

There was definitely beam attenuation going on with BOX. Winds were starting to turn west of north (which is why the dome was attenuated in that direction), so the storm was going to begin to wind down. Like Will mentioned though LWM still had 0.34" between the hours of 5 and 7, so it's not like it was spitting out. It just was shitty snowflakes and a shitty environment to keep them frozen for very long.

Exactly...and as I said to John, it was struggling to accumulate all afternoon in that area.

[Typhoon Tip]

10 minutes ago, OceanStWx said:

There was definitely beam attenuation going on with BOX. Winds were starting to turn west of north (which is why the dome was attenuated in that direction), so the storm was going to begin to wind down. Like Will mentioned though LWM still had 0.34" between the hours of 5 and 7, so it's not like it was spitting out. It just was shitty snowflakes and a shitty environment to keep them frozen for very long.

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?   

[Typhoon Tip]

12 minutes ago, 40/70 Benchmark said:

Exactly my point....even before the precip abated, I was not accumulating efficiently.

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

[STILL N OF PIKE]

30 minutes ago, 40/70 Benchmark said:

It was both.....sure, precip cutoff early in the evening, but it had been accumulating like shit all afternoon, despite heavy fall rates.

There was certainlty a myriad of reason even among different locations

To Johns point and what i saw...Some was actually fall rates like KBED. Look at their observations...They had one hour where they exceeded .10 in the bucket after 250pm. That was not going to get it done. If that was known ahead of time nobody would have forecast near 6" for KBED . HRRR seemed to  hint at  this for that area Sat am.

KBED had hourly totals of 

.09  .10 .15 .08 .03 ending 350 450 550 650 750   .45 over 5 hours of max snow forecast time. Fall rates were an issue in KBED

A spot like LWM seemed more like it was more Surface temps as you mentioned .. they were 1f too mild and you needed an extra 250 to 300' to make a difference. I know in Derry a bit NNW of you they did pretty well (around 6") at 400'

In Maine CP it seemed definitely more of the issue that LWM had.  

 

 

[40/70 Benchmark]

3 minutes ago, STILL N OF PIKE said:

There was certainlty a myriad of reason even among different locations. Some was actually fall rates like KBED. Look at their observations...They had one hour where they exceeded .10 in the bucket after 350pm. That was not going to get it done. HRRR seemed to  hint at  this for that area Sat am

A spot like LWM seemed more like it was more Surface temps as you mentioned .. that were 1f too mild and you needed an extra 250 to 300' to make a difference. I know in Derry a bit NNW of you they did pretty well (around 6") at 400'

 

 

I can tell you that it was low level temps IMBY....may have been overcome due to greater evap cooling had lift been in SGZ, and we had better dendrites, but that was not the case......so we rotted between 33.8 and 34.0 during bulk of heavy precip.

[Lava Rock]

38 minutes ago, OceanStWx said:

Right. Kind of had a partial pupu platter and could never complete the order. 

We had rates, but not the dendrites or low level cold. A little low level cold (elevation) went a long way in this event to help save things. Valleys needed one or the other (dendrites) to come through and neither did. 

In the 8yrs we've lived on tenney hill, this storm produced the largest snowfall gradient over very small elevation changes. A friend of ours lives on Sebago and they only received 1.5". We got 11.5" at 730', yet areas just down the road at ~300' had about half. When I got down towards windham, even less. It's nice when living at some elevation produces during early and late season events. doesn't happen often, but this was the best for us.

[Typhoon Tip]

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 ...  

[ORH_wxman]

1 hour ago, Typhoon Tip said:

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?   

I dunno...the max snowfall for the eastern zones in MA was really like 4-8pm on the model guidance....I agree the models did seem to go on too long after that, but the core of the best stuff was forecasted mostly late afternoon and early evening....which from a rate standpoint, largely verified. Maybe we're having two different discussions here.....

1. Did downsloping affect things later on? Yes. The precip after 7-8pm did not really match model guidance which suggested perhaps 2-3 more inches for E MA even at modest 7 or 8 to 1 rations.

2. Was downsloping the main reason for the lack of snowfall accumulation between 4-7pm? No (IMHO). I think our cross sections are explaining that better with the "perfect storm" of toxic brew....as Chris said, the lower elevations needed either slightly more LL cold or for dendrites to overcome the lack thereof, and we couldn't get either. Places like BED and LWM were getting heavy white rain...slamming plenty of precip into the buckets, but just not accumulating it on the ground.

[Typhoon Tip]

28 minutes ago, ORH_wxman said:

I dunno...the max snowfall for the eastern zones in MA was really like 4-8pm on the model guidance....I agree the models did seem to go on too long after that, but the core of the best stuff was forecasted mostly late afternoon and early evening....which from a rate standpoint, largely verified. Maybe we're having two different discussions here.....

1. Did downsloping affect things later on? Yes. The precip after 7-8pm did not really match model guidance which suggested perhaps 2-3 more inches for E MA even at modest 7 or 8 to 1 rations.

2. Was downsloping the main reason for the lack of snowfall accumulation between 4-7pm? No (IMHO). I think our cross sections are explaining that better with the "perfect storm" of toxic brew....as Chris said, the lower elevations needed either slightly more LL cold or for dendrites to overcome the lack thereof, and we couldn't get either. Places like BED and LWM were getting heavy white rain...slamming plenty of precip into the buckets, but just not accumulating it on the ground.

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' 

[SJonesWX]

at mi casa, it flipped to snow at around 10:45 after about .3” of rain. temp dropped from 36 to 33, and we just rotted on either side of 33 for the rest of the day. the ground got white quickly, and seemed to accumulate quickly. But it was so wet, it just never stacked up. driving around yesterday you could tell that even slightly higher elevations got mor accumulation. interesting storm.

[FXWX]

On ‎12‎/‎5‎/‎2020 at 5:34 PM, dryslot said:

I had it made.

Nice...  I like the look and style... Nothing online the looks anywhere near as nice...