NYC/PHL: December 24-27th Potential

[earthlight]

Euro ensembles essentially track from the Outer Banks over the benchmark. They are still slower than the GFS with the SLP just south/southwest of the benchmark at 138hrs

[tombo82685]

Can someone post the ensembles? Mod- Feel free to delete this post after they are posted. Thank you.

they dont come out to public till 330

[NortheastPAWx]

Euro ensembles essentially track from the Outer Banks over the benchmark. They are still slower than the GFS with the SLP just south/southwest of the benchmark at 138hrs

What's QPF like?

[mattinpa]

they dont come out to public till 330

The ensembles are still a good hit, though, correct?

[earthlight]

...POTENTIAL EAST COAST WINTER STORM AFTER CHRISTMAS...

MODELS SHOW REASONABLY GOOD LARGE-SCALE CONTINUITY IN ALLOWING AN

ANOMALOUSLY STRONG UPPER HIGH OVER GREENLAND TO WEAKEN DURING THE

EARLY STAGES OF THE MEDIUM RANGE PERIOD...WHICH THEN SLOWLY MERGES

WITH AN UPPER RIDGE BUILDING OVER CENTRAL NORTH AMERICA TOWARD THE

END OF THE PERIOD. THE RESULT IS A BLOCKING PATTERN AT THE HIGHER

LATITUDES WITH AN INTENSE POLAR JET STREAM TRAVERSING THE PACIFIC

NORTHWEST WHICH SPLITS...WITH THE SEPARATING FLOWS POSSIBLY

INTERACTING OR PHASING WITH THE SEPARATE STREAMS OVER THE EASTERN

CONUS.

ACROSS THE WEST...THE 12Z GFS IS ABOUT 12 HRS SLOWER THAN THE 12Z

ECMWF WITH THE LEADING EDGE OF A SIGNIFICANT SHORTWAVE TROUGH

REACHING THE NORTHWEST COAST DAY 4...WITH THE FASTER TIMING OF THE

ECMWF SUPPORTED BY THE 12Z CANADIAN/UKMET. THUS...RECOMMEND

DISCOUNTING THE SLOWER AND MORE AMPLIFIED GFS FOR THIS SYSTEM.

EXPECT MULTIPLE ROUNDS OF ADDITIONAL HEAVY PRECIPITATION TO

ACCOMPANY THIS TROUGH...ESPECIALLY ACROSS THE NORTHWEST WHERE 2-5

INCHES OF WATER EQUIVALENT IS ANTICIPATED FOR THE 5-DAY PERIOD

ENDING DAY 7.

IN THE EAST...THE MAIN ISSUE INVOLVES THE INTERACTION OR PHASING

OF MULTIPLE STREAMS OVER THE EASTERN CONUS...WHICH MAY RESULT IN A

SIGNIFICANT EAST COAST WINTER STORM BEGINNING DAY 4. OWING TO

UNCERTAINTY IN INITIAL CONDITIONS...DIFFERENCES IN MODEL

CONFIGURATIONS INCLUDING RESOLUTION...AND DIFFERENCES IN DATA

ASSIMILATION TECHNIQUES...DETERMINISTIC GUIDANCE IN THIS REGION IS

UNUSUALLY SENSITIVE...WITH LARGE DIFFERENCES BETWEEN INDIVIDUAL

MODELS...POOR RUN-TO-RUN CONTINUITY...AND LARGE ENSEMBLE SPREADS.

THUS...THE APPROACH FOR THE EASTERN CONUS SYSTEM IS TOWARD THE

MODEL CONSENSUS AND FORECAST CONTINUITY. THE ONLY ADJUSTMENT MADE

WITH THE FINAL PRESSURES/FRONTS PROGS IN THE EAST WAS TO NUDGE THE

FINAL POSITIONS AND INTENSITY OF THE DEVELOPING CYCLONE TOWARD A

CONSENSUS OF THE LAST 2 RUNS OF THE ECMWF/12Z CANADIAN/00Z ECMWF

ENSEMBLE MEAN...WITH THE FINAL POSITIONS CLOSEST TO THE 00Z ECMWF.

AFTER DISCOUNTING THE 12Z UKMET DUE TO ITS OUTLIER DEPICTIONS IN

MULTIPLE AREAS...THE 12Z ECMWF LIES NEAR THE SLOW OR SOUTHWESTERN

EDGE OF THE ENTIRE GUIDANCE ENVELOPE...AND GIVEN THE MULTIPLE

UNCERTAINTIES HIGHLIGHTED ABOVE...WOULD RATHER SEE ADDITIONAL

GUIDANCE COME INTO BETTER AGREEMENT WITH THE 12Z ECMWF BEFORE

USING ENTIRELY...WHICH IN TERMS OF PROBABILITIES...LIES WITHIN THE

LOWEST 10 PERCENT OF ALL SOLUTIONS...POSSIBLY A LITTLE LESS. IF

THE NEW ECMWF VERIFIES...THE FORECAST TRACK OF THE DEVELOPING LOW

WILL NOT CHANGE APPRECIABLY. HOWEVER...ITS SPEED WILL BE MUCH

SLOWER...RESULTING IN GREATER MOISTURE TRANSPORT FROM THE ATLANTIC

AND THE POTENTIAL FOR HIGHER QPF THAN CURRENTLY FORECAST.

JAMES

[yhbrooklyn]

The Euro is consistent right now, and it's almost in its deadly range. If it's still showing the same thing at 12z tomorrow, then this is the probable solution. Just wow.

What exactly is the Euro's deadly range? I didn't realize it extended past 100 hours.

[tombo82685]

The ensembles are still a good hit, though, correct?

if its taking it right over the bm so i would think so...i havent seen the maps yet, they will be out in 10 mins

[tombo82685]

Thanks Tombo. Love your writeups. I am one who just sits back and reads

thank you, i appreciate it...im sure someone will post them or i will once they are out so people can view them here.

[Stormlover74]

LOL, after last week I'd say 48 hours

What exactly is the Euro's deadly range? I didn't realize it extended past 100 hours.

[winterwx21]

What exactly is the Euro's deadly range? I didn't realize it extended past 100 hours.

I don't think the Euro has been good enough lately to say it has any deadly range. It has been just as inconsistent as all the other models. Remember for the last storm (Sunday) it showed a hit early on...then flipped to a miss for 6 runs in a row...then flipped to a mega hit...then flipped back to a miss. The Euro isn't what it used to be.

[TowsonWeather]

I don't think the Euro has been good enough lately to say it has any deadly range. It has been just as inconsistent as all the other models. Remember for the last storm (Sunday) it showed a hit early on...then flipped to a miss for 6 runs in a row...then flipped to a mega hit...then flipped back to a miss. The Euro isn't what it used to be.

So after the long-range stuff, the Euro was consistent throughout except for a one-run burp, and you are criticizing that performance?

[Bobby]

GFS may be too suppressed. Adjusting the mean surface low track of the more northwestern cluster of its ensemble members 100 miles NW would take a 985-ish low from Hatteras to 39/70 rather than 40/70, which would at least mean all snow, but with the higher amounts across eastern Long Island.

[Stormlover74]

Well yes actually because it was A. 2 runs back to back. one showed us getting a good hit the other a major blizzard and B. these runs were inside 72 hours. The GFS I would expect but if the Euro is king that sort of thing shouldn't occur. Hopefully it means nothing in regard to the current threat but you can't help but have it in the back of your mind.

So after the long-range stuff, the Euro was consistent throughout except for a one-run burp, and you are criticizing that performance?

[njrealtor84]

If you are going to judge consistency and accuracy, you really need to base your statement on a larger sample size. Simply stating one, two or three events will really not suffice. Then also consider the Euro comes out every 12 hours whereas the GFS is about every 6 hours. One could also argue that larger swings should be more frequent in the model that only updates twice a day because of the greater variations in data that can occur over 12 hour spreads, not 6. I believe plenty of the Mets have posted links or comparisons of models.

Well yes actually because it was A. 2 runs back to back. one showed us getting a good hit the other a major blizzard and B. these runs were inside 72 hours. The GFS I would expect but if the Euro is king that sort of thing shouldn't occur. Hopefully it means nothing in regard to the current threat but you can't help but have it in the back of your mind.

[hazwoper]

meanwhile, 18Z NAM out to 60 and further east with the s/w compared to 12Z

[am19psu]

the only thing with the euro thats alarming is that it slows everything down so much more than any of the other models i believe. You speed this up a little bit and you have a further east solution and maybe ots. I think the gem might be more realistic imho

Agree with this, at this time. I know it's not the best model in the world, but it has the most realistic synoptic scenario, imo. It's closest to the Euro Ensemble mean, as well

[hazwoper]

at 66 still slightly further east with s/w compared to 12Z

[Sampson]

meanwhile, 18Z NAM out to 60 and further east with the s/w compared to 12Z

seems like the low is a little further north as well

[NorthShoreWx]

Since some have mentioned it:

http://www.meteo.psu.edu/~gadomski/NARR/1993/031403.png

[TowsonWeather]

seems like the low is a little further north as well

It's a tad East at 66, but not any further north, at least to my eye.

[hazwoper]

72 still further east (50-100 miles maybe) with s/w and the northern stream trying to ge a bit more involved it appears

EDIT - also ridging much more prominant out ahead of system

[hazwoper]

78 - again a bit further east and more ridging ahead of it. I like the looks of the NAM at this point

[Stormlover74]

Well I never said the GFS was the better model, not by any means. All I'm saying is the Euro is not infallible.

If you are going to judge consistency and accuracy, you really need to base your statement on a larger sample size. Simply stating one, two or three events will really not suffice. Then also consider the Euro comes out every 12 hours whereas the GFS is about every 6 hours. One could also argue that larger swings should be more frequent in the model that only updates twice a day because of the greater variations in data that can occur over 12 hour spreads, not 6. I believe plenty of the Mets have posted links or comparisons of models.

[jasonli18t]

Well I never said the GFS was the better model, not by any means. All I'm saying is the Euro is not infallible.

i don't think anyone on this board is under the impression that any model is infallible. The euro is provably the most reliable, though.

[CooL]

Anyone want to throw out guesses on what the NAM will do after 84..sure looks like the phase is underway at that time

[LVblizzard]

Comparing the NAM to the Euro, the phasing seems to be occurring earlier, but in about the same location. This would probably argue for a slightly faster track.

[Rainshadow]

What exactly is the Euro's deadly range? I didn't realize it extended past 100 hours.

Based on this past weekend under 72 hours.

[LVblizzard]

Anyone want to throw out guesses on what the NAM will do after 84..sure looks like the phase is underway at that time

I'd guess it would end up slightly east of the Euro because the s/w is about 6 hours faster. The increased phasing could make up for that, though.

[baroclinic_instability]

the only thing with the euro thats alarming is that it slows everything down so much more than any of the other models i believe. You speed this up a little bit and you have a further east solution and maybe ots. I think the gem might be more realistic imho

I don't disagree with that. I guess I was mostly referencing the massive chasm between the GFS and everything else.

[LVblizzard]

What exactly is the Euro's deadly range? I didn't realize it extended past 100 hours.

A met posted 72-120 was when it had the best verification scores compared to all the other models. I'm pretty sure, but I could be wrong.