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Winter storm for the 25th of February is imminent.


Typhoon Tip
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Complex hemispheric mode changes appear to direct a winter storm across New England; time concerning is very late on the 24th entering SW areas.... but mainly spanning the 25th for all.  This even is > 50% likely to occur.  

Short version of important characteristics:  

-- "Day 5," some latitude in these distinctions is obviously required

-- large spatial dimensions and nuances in the system morphology as its bag of tricks evolves through, may mean a longer duration event relative to the speed in which this thing will be smearing along.  This may touch a lot of the region.  I would not trust QPF limitations due to mid level mechanics - more belw.

-- first as an overrunning stripe with probably icing headlines in the MV, expands along E-W axis over late Wed thru Thurs throughout the OV.  Very proficient QP band with snow/mix/ice/rain, N-->S, will likely be situated from OH-MA overnight Thursday night thru Friday.

-- relative to synoptic mechanics, expect > normal/climo qualitative precipitation, which could even go above QPF. This if for two reasons:  I wonder if PWAT products are entirely correct - this seems it could actually be more laden. The 850 mb trajectories are deep subtropical origin in the Mon/Tues. The other aspect is that as this GOM miasma is foisted N and lops over into the isentropic lifting column on the polar side of the boundary, there situates in tandem a very impressive lateral exit region of A 300 mb jet that spans the entire distance from the eastern Lakes to the lower Maritime.  That would really enhance UVM potential and perhaps situated banding/meso embedded in a ...well, getting too detailed.    That 300 mb jet, and the general concept of bringing a "potentially" hefty PWAT air source into its lifting interface has really been on the guidance' for some time.

-- It's 5 days away, notwithstanding... that said, ice south... mix pounding could results near somewhere between lower CT-RI to the Pike, but the particulars of total synoptic metrics as they situate in the charts ( for now) this is probably mainly snow from ALB-BOS latitudes.  subject to change/get tuned...

-- In all ..what is likely to be in ballast, characterize -able as an overrunning ( proficient one at that!) event, there are hallmarks in the idiosyncrasies that hint at weak Miller B/quasi in form. There is even some suggestion of lag back CCB, albeit week, postponing the storm ends Friday evening for eastern regions.  subject to change/get tuned...

 

Other concepts:  We probably should not ignore the nearer term Tuesday-Wednesday event entirely.  Both it and the following system in question are rooted in the same larger hemispheric scaled changes.  As the onset of a -EPO then wave propagates into the +PNA mode, 

image.png.2c3237c13d457e33df99c35b4a443a9b.png

...that total behavior ( spanning typically a week to 10 days...), tends to first shorten the wave lengths over the downstream continent.  Brief primer: The way that expresses, ...a tall non-hydrostatic height or closed ridge nodes bursts over the Alaskan sector. Immediately downstream, the wave forcing nadirs flow out W ... --> heights rise over the SE/Gulf/SW Atlantic. 

The -EPO ridge/block's gestation then relays into a new height burst ... usually over the SW Canadian latitudes.  The original -EPO either neutralizes, or a new one may take shape ( like 2015!) but there is a time lag between the EPO magnitude and the subsequent PNA.   The 00z Euro demos that total evolution with superb finish... In fact, there's a conceptual signal from multi-guidance for more of a meridional storm event .. between the 27th and about March 4 out there, but... cross that bridge.   

The two systems this week, Wednesday then Friday ... are really like the same event ... only differentiated by their trajectory.  The first is follows the above template by tracking through the Lakes.  The latter system, by virtue of the -EPO --> +PNA, repositions the mean baroclinic zone farther along a S-E axis. 

These large scale changes can take place without Wed or Fri systems.  They seem to be like 'going through the medium as the medium is changing'  In fact, they have been presentable in the various ens systems, ... predating these index explosions were seeing now as having high confidence.  But, the mode changes didn't 'damp' them out as they occurred.  It's really been about re-organizing the circulation and conserving them in the field.   Kind of interesting ... if exceptionally dorky LOL. 

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8 minutes ago, HoarfrostHubb said:

I will delete my thread

Oh shit -- sorry.  You didn't have to do that.   I swear I looked - I did not see a thread yet.   I did mention the last couple of days I was intending to do so but I kept getting pulled away.  Ugh.  Last night it was late ...too tired.. so I suggested somewhere pg 114 of the Feb tread that we should fire one up and that I would if someone else hadn't done so by morning...  I just didn't see it I guess. 

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9 minutes ago, ORH_wxman said:

Canadian held serve and Ukie took a good bump north too. 

GGEM really has been quite striking with that front side/IB signal - more so than the other guidance.  The GFS structures it's frontal positions and jets ( multi layer) in such a way that it could easily be as robust as the GGEM, but is probably lower in total QPF - I'm est - just by eyeballin' the art charts...   

I mentioned this goop at the onset, but my primary concerns are the source/origin of the deep subtropical ingest into the TV baroclinic wall...then, as that overrunning axis lifts to climo position S of LI ( assuming it stops there :yikes: lol ), it moving into a position where the polar side is collocated under a very powerful 300 mb exit region/UVM mechanics. Strikes me as opportunity for QPF 2nd guessing... 

but we got the week to iron it out.

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1 hour ago, Typhoon Tip said:

Oh shit -- sorry.  You didn't have to do that.   I swear I looked - I did not see a thread yet.   I did mention the last couple of days I was intending to do so but I kept getting pulled away.  Ugh.  Last night it was late ...too tired.. so I suggested somewhere pg 114 of the Feb tread that we should fire one up and that I would if someone else hadn't done so by morning...  I just didn't see it I guess. 

It’s all good.  You have had some success lately

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1 minute ago, ORH_wxman said:

Great run for many. Solid snows N of MA/CT border and plenty of sleet and ZR for Kevin which is what he was hoping for. 

Just what he's looking for, Ratios should be a bit better too i think up here then 10:1 but those are details to look at later.

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Just now, dryslot said:

Just looked at soundings, It is warm, We shall see.

I mean we know how these things generally go. The core of the lower level cold is H85 and that's where some of the best WAA is, but when I see H7 starting at -6C at the precip onset it gives me pause on ratios. Maybe we'll luck out with a period of better than 10:1, but I'd just hedge toward the usual SWFE ratios for now.

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