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January Medium/Long Range Discussion


nj2va

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Just now, redskinsnut said:

How is it 10 degrees and dumping snow at epic rates at the same time that there are rain concerns?

Because there are members of the ensemble that cut the storm to our west and we rain. The ensemble members show the range of possibilities. A cutter and rain is definitely one of the possibilities. As is the bomb the op has.

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Just now, Maestrobjwa said:

Seems like it's gonna be harder to get a big one before the pattern really gets going, isn't it? Seems like it's safe to assume cutter unless we see more frozen outcomes depicted by Monday or something...but I guess I'll keep one eye on it, lol

Nothing definitive can ever be said about a storm 8+ days away. All we know is there's probably going to be a fairly strong storm during that time. Mostl likely track/ptype and all that can be figured out over the next 3-5 days. It's not nearly as good a setup as Jan 2016 or either Feb 2010 storms. Those were much easier to figure out with the track. Lots of moving pieces on this one. 

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1 minute ago, redskinsnut said:

How is it 10 degrees and dumping snow at epic rates at the same time that there are rain concerns?

The ensemble of different versions of ECM contain solutions that track further north and mix the precip. If the map you're referring to is accurate, no mixing concerns, would buy ear plugs for the deafening thundersnow. 

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Just now, North Balti Zen said:

Because there are members of the ensemble that cut the storm to our west and we rain. The ensemble members show the range of possibilities. A cutter and rain is definitely one of the possibilities. As is the bomb the op has.

I see thank you

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These panels say it all. EPS has a ridge in the western atlantic 50/50 region. For us to get a good snow event we need low pressure/confluence in that spot.

ecmwf-ens_z500a_nhem_9.png

The euro op had both a -nao and a 50/50 low + confluence. 

ecmwf_z500a_nhem_10.png

 

There's just no way to accurately know how that's going to break. Have a 50/50 + neg nao and odds of snow go way up. Have a western atlantic ridge and expect rain. 

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1 minute ago, redskinsnut said:

How is it 10 degrees and dumping snow at epic rates at the same time that there are rain concerns?

Because the possibility of a cutter is very much on the table. When a storm "cuts" inland, we end up on the warm side of it. That's why temps can surge to 50, but then afterward...it's cold again. Overly simplified explanation, but I think that's the gist of it (other more knowledgeable posters, please feel free to chime in!)

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2 hours ago, Weather Will said:

Bob, Do you or any anyone else know if there have ever been any studies that show that one perturbed member of GEFS has been more reliable than another?  Or am I not understanding how the ensembles work?

 

I think this was sort of already answered...sorry, just catching up in this thread...but I'll add a couple of things if I may.  Basically, ensembles are perturbed members of the base model, and run typically at lower resolution from the operational deterministic version.  How the perturbations are done varies from one model ensemble to the next (e.g., GFS, ECMWF, CMCE, etc.), but they all try to do the same thing...that is, show a range of possible solutions by accounting for various errors (the perturbations) that could be in the regular deterministic run.  In *theory*, you would like to get all possible ranges of solutions, but of course in *practice* that's not possible (would be essentially infinite solutions!).  So various techniques have been developed by different centers...the temperatures may be perturbed, or the pressure/height field, or the physics of the model itself.  I can't recall how each model center does theirs offhand.  If you have more ensemble members in the suite, that should give you a better idea of the spread around the mean.  But just given the fact that you can only have a finite number of ensemble members, and the fact that they're all based on the "same model", you do tend to get what Bob and others call "hive mentality"...i.e., there are many times the ensembles tend to "look a lot like" their parent deterministic model.  However, in general, the ensemble mean is a far better estimate for medium to longer range (I think most consider them useful up to 72 hours out?) than a single deterministic model and a single ensemble member.  To also partly answer another of your questions, I don't believe there's any tendency for one ensemble member to be "better" than the others over time (though of course, a single one can end up being correct in the end).

The ensemble spread is a good thing to look at too, not just the mean.  If the spread is very tight around the mean, that lends more confidence than if they're all over the place.  Likewise, it can give you a clue as to whether the parent deterministic model is an outlier, such as if it's on the extreme edge or outside the envelope of the ensemble spread.  Oh, and when people talk about the "control" run, that's basically a low-resolution unperturbed version of the deterministic (so it's essentially the same as the ops, but lower res).

Sorry for the long-winded explanation, but hope it helps!  And hope I'm reasonably accurate here, others probably know far more on the nuances of the ensembles.

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3 minutes ago, redskinsnut said:

I see thank you

If you were referring specifically to the op run, I would say although that sort of temp gradient can occur in strong coastal storms, it likely would not be as extreme as depicted. Its not likely going to be 10 in the burbs of DC and 35 in Dover. Op run at D10 though.

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1 minute ago, Maestrobjwa said:

Because the possibility of a cutter is very much on the table. When a storm "cuts" inland, we end up on the warm side of it. That's why temps can surge to 50, but then afterward...it's cold again. Overly simplified explanation, but I think that's the gist of it (other more knowledgeable posters, please feel free to chime in!)

We can also, depending on the antecedent cold, end up with quite a good thump of front-end snow, then perhaps ice/sleet, then a dry slot or drizzle or light rain that doesn't totally destroy all the snow that had fallen.  And then, as you say, it gets cold afterward typically.  A good example of solid front-end followed by drizzle was Feb. 2014...many areas got a foot, even more, overnight.  It then warmed into the mid-30s and we had light drizzle most of the remainder of that day, and we actually got some CCB wrap-around snow at the end late day and evening.

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12 minutes ago, Roger Smith said:

The ECM shift to a southern track is plausible, and the GFS concept of chain of lows along a front fails to separate the 19th and 21st energy peaks from my research point of view, so if I blend a better separated GFS with this ECM track, I think you are in the hunt for the jackpot that seems inevitable with the 21st energy peak. More chance of it shifting back north than any further south, it is a finely tuned sports car low that the ECM advertises, and 15-30" certainly in its specs, would toss the 40" though, this is not 1888 and western CT. 

We had 24-36” in 1 storm in this area in 2016. 

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13 minutes ago, Bob Chill said:

These panels say it all. EPS has a ridge in the western atlantic 50/50 region. For us to get a good snow event we need low pressure/confluence in that spot.

ecmwf-ens_z500a_nhem_9.png

The euro op had both a -nao and a 50/50 low + confluence. 

ecmwf_z500a_nhem_10.png

 

There's just no way to accurately know how that's going to break. Have a 50/50 + neg nao and odds of snow go way up. Have a western atlantic ridge and expect rain. 

too early to give up....i think the good pattern is speeding up....with that being said..i expect a 987 in youngstown ohio at 00z

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27 minutes ago, redskinsnut said:

I see thank you

Because it depends on if the northern branch shortwave gets out ahead of the main storm. Bad timing and you don’t build the HP in the ideal spot and heights get pumped out ahead of the low. The Euro OP is pretty much the best case scenario and what can happen if things break right. 

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8 minutes ago, WxUSAF said:

People saying this EPS run is the weeniest of the season? Even after MLK day?

Words do no justice !! 

Storms, below zero cold, cross polar flow, more cold !!!   

The FV3 at long lead has single digit temps to the Gulf Coast. 

Also new UkMet seasonal just out, wow , Nothern Mid Atlantic and the NE target zero for DEEP winter !! 

2cat_20190101_z500_months24_global_deter_public.png

   

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2 hours ago, Bob Chill said:

These panels say it all. EPS has a ridge in the western atlantic 50/50 region. For us to get a good snow event we need low pressure/confluence in that spot.

ecmwf-ens_z500a_nhem_9.png

The euro op had both a -nao and a 50/50 low + confluence. 

ecmwf_z500a_nhem_10.png

 

There's just no way to accurately know how that's going to break. Have a 50/50 + neg nao and odds of snow go way up. Have a western atlantic ridge and expect rain. 

 

In the southeast, I'd certainly agree with that.  That's how we scored down here in December, we had a nice junkyard 50/50 confluence to do work.  I think that's the missing ingredient for our forum at least, that WAR has to go.  We get a real true -NAO and I think everybody scores.  Something like week 4 of the weeklies showed. 

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3 hours ago, Bob Chill said:

Nothing definitive can ever be said about a storm 8+ days away. All we know is there's probably going to be a fairly strong storm during that time. Mostl likely track/ptype and all that can be figured out over the next 3-5 days. It's not nearly as good a setup as Jan 2016 or either Feb 2010 storms. Those were much easier to figure out with the track. Lots of moving pieces on this one. 

I remember how the Jan 2016 storm locked in on the models at 8 days away. Never seen anything like that in my life before. Just run after run after run of perfect hits. Once in a lifetime experience to see such consistency with such a monumental hit come to fruition like it did. 

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11 minutes ago, Bob Chill said:

18z gefs favors rain d8-9 but a long ways to go and we already had one event flip from easy rain to cold powder. Even a mixed event would be great. Anything but 100% rain

Unfortunately with the war being shown across guidance I would favor rain att. But get a well placed vort there or nudge the PV southeast a tad and suddenly we're in business. But man the look towards feb keeps moving closer to the epic weeklies and seasonal guidance look.  

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4 hours ago, Bob Chill said:

18z gefs favors rain d8-9 but a long ways to go and we already had one event flip from easy rain to cold powder. Even a mixed event would be great. Anything but 100% rain

We’re either going to get tstorms or snow at this lead. Seriously. Either way I’m intrigued. 

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