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Ending out December with a Potential Pattern Change


CoastalWx

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One thing has become evident over the last few days. It's going to be a good pattern overall..but the earlier thoughts of it being bitter cold along with all snow events has kind of turned into some snow events/ and some mixed events with a slightly below normal pattern

 

I don't think anybody thought bitter cold and snow. I didn't.

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Yeah there is no need to worry about suppression. Probably more the opposite.

Well I lead that parade of suppression worry and I'm not worried, so no one else should be haha.

Of course you can always get a couple systems to stay way south, and naturally a few will stay SE of up here, but I doubt we will be watching the mid-Atlantic clean up while New England is cold and dry (the New England snow nightmare). It's just not that pattern.

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How come no discussion of snowstorm with the event post Xmas that trended from cutter to cold?

that system is still there - it cuts way west of us now. it's basically just a dry fropa now. earlier the christmas storm was buckling the flow so much that it forced some of that energy way south...so it was a bigger cutter...now you almost don't even see it because there's virtually no trough left behind the xmas storm.

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that system is still there - it cuts way west of us now. it's basically just a dry fropa now. earlier the christmas storm was buckling the flow so much that it forced some of that energy way south...so it was a bigger cutter...now you almost don't even see it because there's virtually no trough left behind the xmas storm.

But it seems like either the 28th or 29th there's an overrunning snow storm on the table now

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How come no discussion of snowstorm with the event post Xmas that trended from cutter to cold?

I dont get what storm you are talking about...12/27?

That one still looks warm...it's just not quite as amped a storm..more like a weak thing that passes NW of us...but there would be no snow with it.

Dec 29th or so looks kind of interesting. But that isn't big news either...the 12/29-12/30 timeframe has been on the ensembles for a few runs now as the first "legit" shot at something after the regime shift...hopefully it looks better as we get closer.

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-NAO strength/duration/location potential takes a hit with tonight's 00z suite completely altering the evolution of the Christmas cyclone

 

This (abv) post got me stinkin' ...

 

I noticed these recent, nearer term depicted attenuations of the Lakes "bomb" ...almost like a punchline, myself.   There may be sort of a transitive causal connection there with the poor handling of the NAO domain, but I really think the truer indictment goes to the PNA handling.  It has been problematic in most the global numerical models I have been following.

 

Nuances in where they have been morphing the +PNA distributed anomalies,  now entering shorter terms, appears to be correcting/shredding that cyclone into a vague impression of the more cohesive signal sold to us last week.  Man, some of those runs drilled that house-sucker down to 952mb!  Rivaling the great Cleveland Super Bomb of 1978... Comparing?  Joke.

 

Now, as of the 12z NAM depiction, just a wavy sort blasse faire frontal boundary, one that even weakens actually by the time it crosses 80th longitude, because so much dynamics have been sheared/absorbed by the mighty SE ridge.  So much so that backside CAA is almost non-existent.  I'm noticing the isobars ~ paralleling the thickness contours post baroclinic axis. 

 

That ridge in the SE is there because ... if we look west to the West Coast, ...there is no ridge over the Rockies. Kind of tough to run a trough in the East ...even the GL longitudes, when the ridge is parked where it is out there; and that is -imho - more of a PNA idiosyncrasy to have a +PNA situate a ridge just off the California coast.  Too far west... 

 

We've coined the expressions "west based" or "east based" when honing in on NAO teleconnector nuances .. That was done because some astute observer once noticed that minute positioning differences more the just seem to play a role in what the circulation medium does between ORD and BOS.  I think of the current PNA dilemma as being a "west based +PNA"; or perhaps more precisely, the PNA distribution is forcing a "west based PNAP" (Perennial North American Patter; which features a low amplitude western ridge/eastern trough couplet in the rest state...)

 

Obviously ... every cause and effect, action and reaction, up down, left right, ...everything that happens in the atmosphere in real time is purely a function of conservation of mass. At the end of all those mind boggling computations using formuli utterly unfathomable to 90% of thinking per capita ... all that math and physics really does is just balance the mass of a the atmospheric fluid medium, based upon temperature and moisture variations moving through it in real time.  

 

That is why teleconnectors work for determining ... the "probability canvas" for lack of better phrase, prior to painting over the charts with all those pips and fronts, lows and highs ... mid level geopotential kinks and closures... etc. Rising or falling modes of these domain spaces MEANS precisely that mass is going to be moving around (balancing).  Those features on weather charts are just a virtual representation of that balancing act, playing out in the 4th dimension: Time.  That's why the Euro is the better model inside certain ranges, because that model has an attempt to take time into consideration ... but I won't get into that further. I've read about only up to a point where I got it intuitively, nothing deeper.  

 

So going forward beyond when the atmosphere's attempt to ruin Christmas is complete ...  personally, if I am pining for winter weather in terms of ptype sensible, meaningful impact, I AM a bit concerned about too much gradient.  That occurred on more than just couple of occasion last year; during historic cold waves, S/W got lost in the raging maelstrom of balanced geopotential winds on the order of a 100kts just about everywhere.  Read this,

http://maths.ucd.ie/met/msc/fezzik/Synop-Met/Ch08-2-Slides.pdf

 

...and struggle or not struggle depending upon one's background, and you may see why... The problem is in those X and Y component derivatives... When the flow is 100kts (say) and a S/W passes into that medium with 110kt jet max... the derivatives are thus weak, and ultimately the QG Vorticity is also ...weak.  Weak DPVA, NO STORM!

 

Buuuut, it is equally axiomatic to note that this is not an absolute limitation at any time.  What if a S/W comes in with 150kts ... then you're limiting factor of having too much initial wind velocity in the balanced mean is not as limiting... The only problem, I don't think it is possible on Earth to get an impulse with endemic 500mb velocity that high outside of a comet impact... I dunno.  300 or 200 mb, sure.  

 

There is going to be an enormous amount of moving parts in this pattern change.  And it really is a change... The multi-day teleconnectors have been persistently hammering the AA phase onset of the N-Pac region, and the subsequent eruption of an EPO ridge is new. Gradient and too much of a good thing is there, perhaps, but getting to whatever "there" is, is going to be a model error tossed salad for a while, more so than usual.  

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Later gator.

Is the 29th you are referring to the same signal that was showing up for NY?

 

The 28th-29th event the Euro shows just offshore is likely not going to happen, the pattern out west is still sort of in a transitional phase and the flow is fast, I'd be surprised if the Euro ends up right on that, the GFS idea of just colder and dry is probably right.

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