Dec 5/6th major coastal/ west Atlantic cyclogenesis ...?

[Typhoon Tip]

Looks like the contention has really been reduced to the amount of phasing between streams.   The GFS is being the stubborn limited outlier ... where there is growing consensus from the other guidance. 

Bit of a guidance battle afoot - 

I know the Euro has taken it's licks in the last couple years ...I almost sense/think that the speeding up of the hemisphere in the means is presenting specific challenges to that particular model ... It's sort of like the arena is changing on it and it's 4-D corrective algorithm genius is getting out-moded ... But that's obviously intensely speculative - ha!  

Anyway, the GFS really almost has no phase even though we are but 90 hours from supposed max impact by the zesty Euro/NAM/GGEM blend...which show substantially more.  The GFS's unwillingness really materialized the moment all the models gave up on the latter system for the 7th/8th/9th of December in lieu of this one for the 5th/6th ...  The previous GFS solution interestingly showed more phasing ..but when this came back into scope, it's just not getting on board. 

I'm willing throw myself under the bus and wager that the GFS is less correct in this case.  Tho all models have their annoying little gem biases ... the GFS has a speed bias ( in a fast hemisphere as it is, which hides its bias ironically ...) and thus, I don't think it is handling the delicate speed handling in the phasing harmonics of the N and S stream wave mechanics.   Some pricey words to describe that it's not really the right model to spearhead this storm's project - ha.  

That said, we'll still be nailing down particulars with timing and track... but for now, I'm inclined to strong coastal/ near by cyclogen that may approach bombogenesis...and I also think going from a relative warm column to a deeply imploding mid tropospheric height core as this thing's thermodynamic processing is passing through... sends some interesting convection signals... Supposing a Euro solution verifies, we probably have this sort of thing to contend with from NE CT to southern Maine, 

"...Forecasting such convective snow events is made even more difficult by the meso-β scale banding (with halfwidths of approximately 100 km) that is usually observed in these events. Moore & Blakely (1988), Weismuller & Zubrick (1998), Nicosia & Grumm (1999), and Martin (1998a, 1998b) have all presented case studies in which meso-β bands of heavy snowfall fell in regions of otherwise light to moderate snowfall, likely in the presence of either potential instability (PI), conditional symmetric instability (CSI), or weak conditional symmetric stability (CSS). PI is a state of the atmosphere where a lifted layer achieves a statically unstable lapse rate, resulting in upright convection....."   C/o https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1017/S1350482703003074

Very important caveat emptor:   If the GFS solution is right, ...none of this will happen   

[WinterWolf]

Shouldn’t your title read:  I figured I “Wouldn’t“ doom the storm at all?  Not sure that part makes sense as is?  Or what you’re trying to say there?  Maybe it’s just me? 

[Typhoon Tip]

I wouldn't worry about titles of threads ...   heh

but if we must, sarcasm  ?   

"I figured I'd doom for merely posting" being the sarcastic jest - 

[ORH_wxman]

18z NAM southern stream dragging its heels big time vs 12z. This will either be well east of 12z or end up as solely a southern stream event this run (think more like the GFS type solutions we've seen the past day or two)

[PhineasC]

3 minutes ago, ORH_wxman said:

18z NAM southern stream dragging its heels big time vs 12z. This will either be well east of 12z or end up as solely a southern stream event this run (think more like the GFS type solutions we've seen the past day or two)

East march will continue. I’m afraid the 12z Euro may have been the high water mark. 

[Typhoon Tip]

4 minutes ago, ORH_wxman said:

18z NAM southern stream dragging its heels big time vs 12z. This will either be well east of 12z or end up as solely a southern stream event this run (think more like the GFS type solutions we've seen the past day or two)

Hey ... I meant that caveat emptor ...  'if the gfs solution pans out ... fo' gettabouit'

[Typhoon Tip]

I bet the the 18z Euro holds - 

or

...we can finally at last petition the gov to discontinue owing tax dollars to that particular org - hahaha

[Typhoon Tip]

Hmm.. play-by-play on the NAM beyond 36 hours ...  be that as it may, I think this solution still phases...may later ... but I'm only out to 66

[dryslot]

It is phasing late, Will be east of 12z, I'm at hr 78, Nuke.

[ORH_wxman]

Yeah this is a really late phase....slower system too.

[dryslot]

It really slowed down this run from 12z, The s/w bowling ball down south was dragging its heels.

[powderfreak]

84

[PhineasC]

Better than 12z here. Just need the NAM to not change for the next 80 hours. Not an issue!

[ORH_wxman]

Not as dynamic as 12z....owing to the southern stream staying separate for longer. Still a pretty impressive system, but not the utter nuclear bomb that 12z was.

[dryslot]

Air mass is just so borderline, You're going to need all the dynamics you can get.

[PhineasC]

NAM even wraps snow back around to my house in MD. 

[ORH_wxman]

Just now, PhineasC said:

NAM even wraps snow back around to my house in MD. 

The upper level system is pretty strong still to the southwest so if we had another frame or two, it might still enhance the CCB across new england. Still not the obscenity that 12z was, but the slowness of this run prevents us from seeing the full potential because that probably happens at 90 hours or so.

[Typhoon Tip]

2 minutes ago, ORH_wxman said:

Not as dynamic as 12z....owing to the southern stream staying separate for longer. Still a pretty impressive system, but not the utter nuclear bomb that 12z was.

I wonder why it took so long I mean I'm not complainin' ...it's the NAM deep field .. .but why it took longer to bump that placeholder through the lower OV.. ? interesting - 

[PhineasC]

Just now, ORH_wxman said:

The upper level system is pretty strong still to the southwest so if we had another frame or two, it might still enhance the CCB across new england. Still not the obscenity that 12z was, but the slowness of this run prevents us from seeing the full potential because that probably happens at 90 hours or so.

Need to run the NAM to hour 102. LOL

[dryslot]

It looked like if we had a couple more panels because it slowed down so much that it would've pivot back to the west some.

[CoastalWx]

S/w was still well offshore. Like others said, weenie extrapolation may bring the snows east some.

[40/70 Benchmark]

19 minutes ago, dryslot said:

It is phasing late, Will be east of 12z, I'm at hr 78, Nuke.

 

17 minutes ago, ORH_wxman said:

Yeah this is a really late phase....slower system too.

You don't say?

[HoarfrostHubb]

34 minutes ago, PhineasC said:

East march will continue. I’m afraid the 12z Euro may have been the high water mark. 

Well...yeah... it isn't like it would improve

[PhineasC]

3 minutes ago, HoarfrostHubb said:

Well...yeah... it isn't like it would improve

There is always room for more. There are additional colors available on the clown map legend, silly! Where is the DGEX when you need it?

[Hoth]

Just give me a few mangled flakes at the end. That's all I ask.

[Ginx snewx]

We really discussing the NAM at 78 84 like it has a clue?

[DTWXRISK]

The Friday night Saturday system seems to be ideal for a heavy rain going over to snow event especially on the   12z WED    EURO  solution.  Even if we assume that the European solution here is correct   -- it may not be  -- and the actual track of the LOW  is further to the East and it is  going to move off the coast  earlier than what the previous  runs of the  Euro were showing .  the problem is the lack of low-level cold air.

 At 9z  SAT  the  12z  EURO has the LOW in Hampton Roads   --  I have drawn in the  0c  850mb  isotherm in Orange and the 32 degree temperature line at the surface in purple.  NOW if this was the middle of winter this heavy rain would be changing over to snow in the entire Shenandoah Valley as well as the mountains of Western North Carolina Southwest Virginia and pretty close to the Washington DC area certainly northwest Virginia     as well as interior Southeastern Pennsylvania.

Indeed looking at the  72 hrs  euro  valid 12z   SAT   it is  clear that the 0c  850mb  isotherm has been pulled into the coast as the Nor'easter is developing off the Delmarva. And again if this was the middle of winter…  the rain could possibly change the snow as far south as Richmond and east of Washington D.C Baltimore and Philadelphia.   ( if my Grandmother had balls she would be my  Grandfather….)

But as the image on the right shows the low-level temperatures are simply too warm to support any snow except for perhaps the Shenandoah Valley./    western   MD   south central PA.   But even there  temperatures of 35 and 37 degrees  are not going to allow for any kind of accumulation even if it does end as snow. 

 

The   500mb pattern seems to be ideal Friday night going into Saturday morning. The two short waves clearly phase in the pre-dawn hours of Saturday which allows the southeast LOW to undergo significant intensification and bomb out as the shortwave goes negative off the Middle Atlantic Coast on Saturday morning 

 

 

The operational European goes kablooie with the system and as a monster raging Nor'easter Saturday afternoon evening. This is clearly an elevation snow which was what the precipitation type surface  maps are clearly depicting. Even if you look at the surface temperatures for late Saturday afternoon Boston is still in the mid 30s es as is all of Southeastern Massachusetts Rhode Island and most of coastal and interior  CT.


The snowfall accumulation map from the operational European on both weathermodelS and weatherbell are simply  BULLSHIT 

It is  clear that they continue to measure mixed precipitation --which is what much of the precipitation in central or western Massachusetts will be ---as all snow.

 Moreover if you compare the more accurate and far more reasonable snowfall maps from    eurowx.com   you can see that their  snow algorithm is far more reasonable and makes accurate   and makes sense given the  Upper air  pattern and the model surface development of this Coastal storm. The differences in the snowfall amounts in Central and Western Massachusetts is astronomical.

in summary this event for Friday night into Saturday is a classic East Coast Nor'easter and   supports   adage that early December is very difficult to get a major pure East Coast snow storm because of the still relatively  mild sea  surface water temperatures.  Not impossible just difficult

The choice is up to you. I'm sure some of you rather have the ridiculous over-amped over done snowfall maps from the European or the GFS. It seems that the operational European so far this cold season is way over doing the snowfall amounts as we saw with the Ohio Valley storm last week and now this one.   This event is only 72 hours away so usually the European model Gets a Clue at this point rather than going bonkers with the snowfall  totals.. 

Of course if the European model is acting funny this cold season and is over doing the snowfall amounts and this is going to be a  forecast problem.    The only way in my opinion to get around this is to check these ridiculous snowfall amounts from these other websites with the snowfall maps from EURO   WX.COM ….   which seems to be   far superior to anything on whether Bell or weather models.

[DTWXRISK]

32 minutes ago, dryslot said:

Air mass is just so borderline, You're going to need all the dynamics you can get.

BING   ****ING  GO 

[PhineasC]

Holy shit DT in the house. 

[MarkO]

I bet he's sick of the mid-atlantic rains and eyeing a move into Phin's backyard and elevated another 100' to steal the New England Snow top spot owner.