March 2-4th ... first -NAO anchored storm perhaps in years

[griteater]

2 hours ago, Typhoon Tip said:

There's larger scaled problems with the "true stall" scenario .. hemispheric in scope/caused really.   Although, slow movement is still underway, that may in part be the mechanics of deepening during closing off tending to temporarily countermand the surrounding steering .. 

Said steering was thought to be less coherent during this time as the NAO blocking's retrogression approached the Maritime regions, understandably. However, that is/was not the case.  That part has both failed (partially) but is also not normal for -3 or -4 SD NAOs that are west-based...  East based? That may be more likely ...  but with west-based, we should be maximizing the breakdown of the normal west to east resonance of the atmosphere - hence the term "retrograde." Thus, as system evolutions of this ilk, as history has shown, would stall.

So what's up?    ...Well, I'm looking at the Euro and GFS' two 00z and 06z cycles and they all expose that the SE ridge is still very much intact. There's been conjecture that the SE ridge would decay as this NAO evolved and that may certainly be true (or not...). Regardless, as of this day, it is there supplying a progressive force on this entire system's construct.

It's merely being compressed by this things migration over the top... Here's the problem, in terms of wave mechanics and offsetting to the stall is that it speeds up the flow in between and that's the source of the partial if not total breakdown in stall/retrograde capability. You can't really stall a deep layer vortex ivo  ISP when you have large scale planetary wave mechanics literally pushing this thing along from the south, such that these two annotations above more than merely suggest.  I used to refer to this as the "Miami rule" back in the day... and it has to do with heights and or balanced geostrophic winds over that raob site.  If the heights are greater than ~ 582, and/or the wind is moving fast than ~ 35 kts, that means that whether the model "looks" like it or not, there is in fact some sort of negating ridge tendency that will offset and/or perturb waves as they move through the eastern North American middle latitudes.  This stung the forecast community back in March of 2001 ... when it caused that event/deep anomaly to rather uncharacteristically foist too quickly east to involve the M/A region as much as it appeared would be the case as little as three days prior to that event.   

I also suspect it has an indirect cause to why we have the two main global models indicated < 525 DAM core heights passing under LI with snow having problems on the N wall of that container.  That depth and liquid do not usually happen together; I believe the SE ridge and perhaps more importantly ...  the general -PNAP flow that this thing is evolving through sort of tore up the lower troposphere and made for an unusual thermal layout relative to this sort of thing's evolution.  This whole -NAO period is really fraught with nuances..  At the end of all this and 140 whatever pages of this thread, I think we simply are at war between the Pacific and the N. Atlantic, and this system's idiosyncrasies are a direct result.  

 

 

1 hour ago, Typhoon Tip said:

Exactly ... not to drop names, but.. when I interned with Harv ...back in the last Century ... he clued me onto the notion of "where is the actual long-wave" - which I suspect is his own way of addressing this stuff.  I recall vividly we were discussing it when we were going over charts ...and trying to assess where a system affecting our region would probably get to it's strongest amplitude...etc..etc.. But, this isn't a full latitude system - that may be the first clue. The lower latitude wave trough configuration is really sort of out of sync with the stream this system is embedded in... fascinating. 

In this situation it is interesting,  ..we get to that amplitude probably as this is drifting SE this evening... but, the actual real "stall" lat/lons are as you suggest, somewhere meandering out there NE of Bermuda or something.  

Here's a loop to supplement your well laid out thoughts.  It shows the above normal heights in the deep south and gulf as the storm moves into the NE, along with the subsequent slowing of the system and dramatic trough deepening in the western Atlantic as negative heights plunge into the Caribbean.

One thing that comes to mind for me here is that I've always felt that the configuration and placement of the -NAO low anomaly south of the blocking ridge is more important than the blocking ridge itself.  In this case, the low anomaly under the Greenland ridge is in the eastern Atlantic.  So the blocking ridge has retrograded into Greenland (west based or moving into west based), but the low anomaly underneath the blocking ridge is still east based in the eastern Atlantic.

[Massplow]

First time posting but have been on here for years. Wondering what time this will change over to snow in the Hyde park Dedham area and if you guys think it’ll stick ? I plow parking lots wondering if we’re going to need to go out or not

[Baroclinic Zone]

12 minutes ago, Massplow said:

First time posting but have been on here for years. Wondering what time this will change over to snow in the Hyde park Dedham area and if you guys think it’ll stick ? I plow parking lots wondering if we’re going to need to go out or not

Sometime towards the evening.  My guess is between 6-8pm.

[Massplow]

8 minutes ago, Baroclinic Zone said:

Sometime towards the evening.  My guess is between 6-8pm.

Ok thanks. These type of storms are always real tough with calling people in. 

[CT Valley Snowman]

20 hours ago, CTValleySnowMan said:

I'm leaning light on snowfall for this location.  Maybe a slushy inch or two, could even get shutout if everything breaks wrong. Maybe I'll be surprised with more but most models do not like north central Ct and the southern Pioneer Valley.  Boundary layer is an inferno, and by the time the ML temps start crashing the best forcing/firehose shifts east and south and we kind of get jumped over here with some catpaws to finish.  Hopefully I'm wrong but that's kind of the way I'm seeing things.

 

Seems like things are pretty much going as I expected for this location.  Had about 1 hour of huge flakes that never managed to accumulate.  Back to light rain and thinking the best forcing from the firehose may focus SE of here from here in.  

[Baroclinic Zone]

5 hours ago, Baroclinic Zone said:

Sometime towards the evening.  My guess is between 6-8pm.

Well this won't pan out.