NYC/PHL December 24-27 Potential - Part 2

[tombo82685]

The exact low placement is most signficiant in this example. It was 1000 miles off.

-Snow

ok that i will deff give you, but its showing a snowstorm when it really might not be.

[eduggs]

Those are only a few model maps. I don't want to overrun the forum with a ton of JMA images.

We need statistics, not images. I have dozens of Euro blizzard maps stored in my head that never came to be.

[Snow_Miser]

ok that i will deff give you, but its showing a snowstorm when it really might not be.

The snowstorm may be debatable, but the lack of QPF in Minneapolis (which actually was the system that caused the roof collapse due to all of that heavy snow) is not shown in the JMA.

[Snow_Miser]

We need statistics, not images. I have dozens of Euro blizzard maps stored in my head that never came to be.

If one model was statistically proven to be more accurate than another, do you think that the Japanese Meteorological Association would continue the JMA model?

[eduggs]

If one model was statistically proven to be more accurate than another, do you think that the Japanese Meteorological Association would continue the JMA model?

Of course.

[eduggs]

The snowstorm may be debatable, but the lack of QPF in Minneapolis (which actually was the system that caused the roof collapse due to all of that heavy snow) is not shown in the JMA.

As I remember it, many, if not most model runs around that time did not bury MSP.

[Snow_Miser]

As I remember it, many, if not most model runs around that time did not bury MSP.

ECMWF was the most consistent, and the "western outlier" and the models gradually trended towards it as they are doing now.

[blizzardof09]

ECMWF was the most consistent, and the "western outlier" and the models gradually trended towards it as they are doing now.

well you got a point there the models are coming into more of a consensus of going with a euro sloution, although i doubt its gonna be that massive of a storm as depicted on the 12z model run.

[Snow_Miser]

well you got a point there the models are coming into more of a consensus of going with a euro sloution, although i doubt its gonna be that massive of a storm as depicted on the 12z model run.

Euro may be overdoing it, but I think that it is better, track wise for this storm's eventual outcome.

GFS was showing a "bowling ball storm" before, before it switched to the Euro's Miller A solution.

[eduggs]

Euro may be overdoing it, but I think that it is better, track wise for this storm's eventual outcome.

GFS was showing a "bowling ball storm" before, before it switched to the Euro's Miller A solution.

Where they are now similar is that the GFS is now suppressed with the initial s/w like the Euro has been for a few runs. It's not clear to me this is a good thing. What saves us on the Euro is the incredible deepening and amplification of the trof structure just in time to capture the SLP. None of the GFS or GGEM ensemble members pull this off. The Euro could be wrong in this feature despite being correct initially... if so, this misses SE.

[Snow_Miser]

Where they are now similar is that the GFS is now suppressed with the initial s/w like the Euro has been for a few runs. It's not clear to me this is a good thing. What saves us on the Euro is the incredible deepening and amplification of the trof structure just in time to capture the SLP. None of the GFS or GGEM ensemble members pull this off. The Euro could be wrong in this feature despite being correct initially... if so, this misses SE.

GEFS and GGEM Ensembles are usually E of the Op. when they agree with it. They showed a similar look to what the JMA showed earlier for the Dec 9th Rainstorm- a coastal snowstorm.

The GFS also is cruddy with the Northern Polar Jet. It has an excellent Southern Jet, and if that Northern jet were to be a bit better, you'd have a scenario like the Euro. One tiny seemingly innocuous detail like that can significantly impact our storm.

[Alpha5]

Looks like the GGEM/Euro vs the GFS now.....funny how the GFS always seems to come up with a new solution around 120 hours after being consistent with a previous solution for so long.

[Snow_Miser]

Looks like the GGEM/Euro vs the GFS now.....funny how the GFS always seems to come up with a new solution around 120 hours after being consistent with a previous solution for so long.

That's the GFS for you!

[atownwxwatcher]

Where they are now similar is that the GFS is now suppressed with the initial s/w like the Euro has been for a few runs. It's not clear to me this is a good thing. What saves us on the Euro is the incredible deepening and amplification of the trof structure just in time to capture the SLP. None of the GFS or GGEM ensemble members pull this off. The Euro could be wrong in this feature despite being correct initially... if so, this misses SE.

Would not the blocking argue for a slowing down of the S/W which allows for the phase and thus the capture as depicted by the ECM? This is essentially what HPC had said last night in its overnight discussion..

[blizzardof09]

Would not the blocking argue for a slowing down of the S/W which allows for the phase and thus the capture as depicted by the ECM? This is essentially what HPC had said last night in its overnight discussion..

yea the blocking would def slow the s/w down for sure , hence the euro as you said picking up on this and factoring that into its model run

[donsutherland1]

For those who are interested, the following are the 12z ECMWF ensemble mean (left) and operational ECMWF (right) from 120 hours through 168 hours.

As noted previously, I suspect that the ECMWF is holding the system back too long and that is leading to a solution that is probably too wound up and too close to the coast. I suspect that a compromise between the 0z/12z ECMWF ensemble mean and 12z GFS ensemble mean probably offers a reasonable solution.

[Snow_Miser]

For those who are interested, the following are the 12z ECMWF ensemble mean (left) and operational ECMWF (right) from 96 hours through 168 hours.

As noted previously, I suspect that the ECMWF is holding the system back too long and that is leading to a solution that is probably too wound up and too close to the coast. I suspect that a compromise between the 0z/12z ECMWF ensemble mean and 12z GFS ensemble mean probably offers a reasonable solution.

Blocking to the N and E would allow this storm to slow down.

[Snow_Miser]

yea the blocking would def slow the s/w down for sure , hence the euro as you said picking up on this and factoring that into its model run

GFS will probably have an epiphany sooner or later. Probably at 0Z is my best bet. If not 0Z, then 12Z tomorrow.

[atownwxwatcher]

After all this is indeed even what HM seemed to be implying....

A quick update before I head out:

The MJO pulse described in the original post is turning out to be quite impressive, initiating the Atlantic invest and Pac storm. The upward motion has been completely weakened across the Indonesian sector based on the latest OLR/CHI anomalies. It has also become quite apparent that the 12/25-26 storm is legit and likely the Heather A. signal. The slower progression of the s/w from the Southwest and monster blocking has completely allowed for the potential of a monster coastal storm. I look forward to tracking this one with all of you.

[Snow_Miser]

Mt. Holly says NO to the GFS.

http://forecast.weat...1&highlight=off

In case anyone didn't see this...

[donsutherland1]

Note: The animation isn't working. I'm receiving a null object indexing error at AmericanWx. I apologize that one cannot see the animation.

[am19psu]

Interesting... all three of those show a bomb on the coast...

Yeah, I think there will be a coastal and I think SNE is going to get pounded, i'm just questioning how much south of NYC gets. If I get to use old models, I actually like the 21/0z ECM the best.

For those who are interested, the following are the 12z ECMWF ensemble mean (left) and operational ECMWF (right) from 120 hours through 168 hours.

As noted previously, I suspect that the ECMWF is holding the system back too long and that is leading to a solution that is probably too wound up and too close to the coast. I suspect that a compromise between the 0z/12z ECMWF ensemble mean and 12z GFS ensemble mean probably offers a reasonable solution.

Yeah, Don. That's kinda why I like the GEM. Looks like the 12z ECM Ensemble and makes more synoptic sense.

[donsutherland1]

In case anyone didn't see this...

The NWS offices have a number of great discussions this evening ("must read" IMO) that highlight the significant uncertainty that still exists.

For example, BOX explains:

GFS AND ITS ENSEMBLES REMAINS CONSISTENT WITH PAST FEW RUNS IN

WHIZZING THE STORM OUT TO SEA QUICKLY...GIVING US A SHOT OF SNOW

SATURDAY NIGHT INTO SUNDAY. GFS DID NOT HAVE THE BEST TRACK RECORD

HOWEVER WITH THIS PREVIOUS STORM AND ALL OF THE SNOW ON CAPE COD

YESTERDAY.

THE CANADIAN GGEM HAS BY FAR THE MOST PROLIFIC PRECIPITATION

AMOUNTS. ITS SURFACE LOW DEEPENS TO 977 MB SOUTH OF THE EASTERN

TIP OF LONG ISLAND. HEAVY SNOW WOULD BREAK OUT ACROSS ALL OF

SOUTHERN NEW ENGLAND ON THE FRONT END...FOLLOWED BY A CHANCE TO

RAIN IN THE EASTERN THIRD OR HALF OF THE AREA WITH THIS SCENARIO

AND WARMING ABOVE 0C SUNDAY NIGHT. WELL OVER A FOOT OF SNOW WOULD

OCCUR ON THE FRONT END. EASY TO GET EXCITED ABOUT THIS...EXCEPT

THAT IRONICALLY ALL OF THE GGEM ENSEMBLE MEMBERS ARE WELL TO THE

EAST...MORE IN LINE WITH THE GFS...THAN THE OPERATIONAL GGEM RUN.

THE 12Z ECMWF IS ALSO VERY IMPRESSIVE...WITH A LOW BOMBING TO 963 MB

OFF THE IMMEDIATE NEW JERSEY COAST...AND MUCH SLOWER THAN THE

OTHER MODELS WITH NO PRECIPITATION HERE UNTIL SUNDAY NIGHT. IT TOO

WOULD GIVE A DUMPING OF SNOW ON THE FRONT END FOLLOWED BY A CHANGE

TO RAIN IN THE EASTERN PART OF THE AREA. ITS TWIST IS THAT THE

UPPER AND SURFACE LOWS THEN SLIDE EAST TO EXACTLY THE BENCHMARK OF

40N 70W CAUSING ANY RAIN TO CHANGE BACK TO SNOW MONDAY THROUGH

MONDAY NIGHT. IT IS THE WESTERNMOST OUTLIER AT THE MOMENT. WILL

HAVE TO MONITOR ITS TRENDS.

OKX states:

WEAK RIDGING ACROSS THE AREA FRIDAY NIGHT INTO SATURDAY MORNING.

MODELS STILL IN GENERAL AGREEMENT WITH A COASTAL LOW PRESSURE MOVING

UP THE EASTERN SEABOARD FOR THE CHRISTMAS WEEKEND. AT THIS TIME THE

EXACT EVOLUTION INCLUDING TIMING AND TRACK DETAILS OF THE STORM

SYSTEM REMAIN UNCERTAIN. THE GFS CONTINUES TO FLIP FLOP FROM PREVIOUS

RUNS. THE 12Z/GFS IS NOW FASTER...LESS AMPLIFIED AND OUTSIDE OF THE

70/40 BENCHMARK. THE 12Z/ECMWF...ALTHOUGH STILL INSIDE THE 70/40

BENCHMARK...IS MUCH SLOWER BRINGING PRECIP INTO THE AREA SUNDAY

NIGHT INTO MONDAY AFTERNOON TIMEFRAME.

PRECIPITATION...ATTM IT APPEARS THAT THE LOW WILL TRACK CLOSE ENOUGH

TO BRING PRECIP TO THE LOCAL AREA BUT ANY SHIFTS IN THE TRACK OF THE

COASTAL LOW WILL PRODUCE SIGNIFICANT CHANGES TO POTENTIAL SNOWFALL

AMOUNTS.

PHI adds:

SOME OF THE MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT, BUT

THERE REMAINS ENOUGH OF A SPREAD AND AT DAY 5, THIS STILL REMAINS

A LOWER THAN AVERAGE CONFIDENCE FCST.

ONE TREND THAT HAS DEVELOPED IS THAT VIRTUALLY ALL OF THE

GUIDANCE, WITH THE EXCEPTION OF THE GFS HAS TRENDED SLOWER WITH

THE UPCOMING STORM. AS A RESULT, CHRISTMAS DAY NOW LOOKS DRY,

DEPENDING ON THE ULTIMATE TIMING, SATURDAY NIGHT COULD END UP

MOSTLY DRY AS WELL.

VIRTUALLY ALL OF THE MDLS WANT TO BRING AT LEAST SOME PRECIP TO

THE AREA DURG THE SUNDAY INTO MONDAY TIME FRAME. THE MAIN

QUESTIONS REMAIN THE TIMING ULTIMATE PATH OF THE STORM WHICH WILL

AFFECT PRECIP AMTS (AND PSBLY PRECIP TYPE AS WELL).

THE 12Z GFS HAS A MUCH WEAKER SFC LOW, VIRTUALLY NO WELL DEFINED

VORT AND AS A RESULT IS MUCH MORE PROGRESSIVE WITH THE H5 PATN AND

KEEPS A MUCH WKR SFC LOW WELL TO OUR S AND E. THE 12Z GFS SOLN IS

AS CLOSE TO A NON-EVENT AS THE MDLS ARE SHOWING ATTM. HOWEVER, THE

GFS IS THE OUTLIER AND IS BEING DISCOUNTED ATTM.

THE 12Z UKMET HAS STUCK TO ITS GUNS ONCE AGAIN WITH A MORE ELY

SOLN, EVEN THOUGH IT HAS TRENDED WWD WITH ITS LATEST CYCLE. ITS

POSN AT 27/12Z IS WELL OFF THE NC CST. THE UKMET TENDS TO BE ONE

OF THE MORE RELIABLE MDLS, SO WHILE IT IS AN OUTLIER WITH THE

LATEST MDL CYCLE, IT REMAINS TO BE SEEN IF IT WILL CONTINUE TO BE

SO.

THE LATEST CMC HAS TRENDED A BIT SLOWER AND FURTHER E AT 12Z,

AFTER A MARKED WWD SHIFT LAST NIGHT. ON THE OTHER HAND, THE 12Z

ECMWF HAS TRENDED SLOWER BUT FURTHER W. BOTH THE CMC AND ECMWF

SOLNS WOULD BE A MORE SIGNIFICANT EVENT FOR THE REGION, WITH THE

ECMWF POSN ULTIMATELY BRINGING PRECIP TYPE INTO QUESTION

ESPECIALLY FOR SRN AND ERN SECTIONS.

THE LATEST NAEFS STILL INDICATES MORE OF A GLANCING BLOW FOR THE

REGION, WITH THE INDIVIDUAL MEMBERS PRESENTING ALL DIFFERENT

SCENARIOS.

SO, WHAT DOES THIS ALL MEAN? WELL, UNCERTAINTY PREVAILS, AS IT

SHOULD AT DAY 5, BUT INDICATIONS ARE THAT AT LEAST SOMETHING WILL

OCCUR IN THE SUNDAY/MONDAY TIME FRAME. AGAIN, THE UKMET WOULD AND

GFS WOULD INDICATE THE MOST MINIMAL EVENTS WITH THE CMC AND ECMWF

BEING MORE SIGNIFICANT. THE ULTIMATE TIMING, TRACK AND INTENSITY

OF THE LOW DETERMINE WHAT OCCURS AND THOSE DETAILS WILL HOPEFULLY

BE REFINED BY THE MDLS IN THE COMING DAYS. MDL POSNS VARY EXCEPT

FOR THE CMC AND ECMWF, WHERE THERE ARE TIMING DIFFS

LWX explains:

LOW PRESSURE IN THE SOUTHERN BRANCH OF THE JET WILL TRACK THROUGH

THE DEEP SOUTH FRIDAY NIGHT AND EVENTUALLY OFF THE SOUTHEAST COAST

SATURDAY. AT THE SAME TIME...ENERGY FROM THE NORTHERN BRANCH OF THE

JET WILL BE DIVING SOUTHEAST INTO THIS SYSTEM. AS THE TWO SYSTEMS

PHASE TOGETHER...LOW PRESSURE IS EXPECTED TO STRENGTHEN AS IT TRACKS

UP THE MID-ATLANTIC COAST SATURDAY AND TOWARD NEW ENGLAND SUNDAY.

THERE REMAINS A GOOD DEAL OF UNCERTAINTY WITH THE TRACK...TIMING AND

INTENSITY OF THE SYSTEM. IF THE LOW INTENSIFIES QUICKLY AND REMAINS

CLOSE TO THE COAST...THEN A SIGNIFICANT SNOW IS POSSIBLE ACROSS THE

AREA DURING THE HOLIDAY WEEKEND. IF THE LOW IS WEAKER AND FURTHER

AWAY FROM THE COAST...THEN SNOWFALL AMOUNTS WILL BE LIGHT. THE BEST

TIMING FOR SNOWFALL AS OF NOW APPEARS TO BE SATURDAY INTO SUNDAY.

.

[NortheastPAWx]

Yeah, I think there will be a coastal and I think SNE is going to get pounded, i'm just questioning how much south of NYC gets. If I get to use old models, I actually like the 21/0z ECM the best.

Yeah, Don. That's kinda why I like the GEM. Looks like the 12z ECM Ensemble and makes more synoptic sense.

Do you think the QPF shield on the GGEM should wind up better than it did on its 12z run?

[am19psu]

Do you think the QPF shield on the GGEM should wind up better than it did on its 12z run?

That's more of a mesoscale thing that will be refined leading up to the event. I'm more worried about synoptics right now. To answer your question, I would say yes, but only because that's what "normally" happens. I haven't given it much thought.

[OSU2]

It's been a long time but I figure a post here and there is not a bad thing.

From my internal update from earlier this afternoon.

Playing it conservative for now.

PHL Weather Update: Amazing Model Differences Regarding Weekend Storm: (All Has To Do With Timing Of Energy): GFS-Light Snow-No Phase:/EURO-Full Phase-Historic Snowstorm:

PM UPDATE: 2PM No changes to the short-term forecast through Friday. The AM Weather Points look good from early this morning. All eyes to the weekend. WOW, amazing model differences for the 12Z Model Cycle and it has everything to do with timing of upper level features. Energy is just entering the West Coast with individual models handing the timing and speed of energy differently, hence major model differences. As stated many times before, if and where phasing of the Southern and Northern Stream occurs will be key. The 12Z GFS is showing a much faster solution then other guidance with no phase and a flat wave of low pressure ejecting out of the Plains, aka a period of light snow for us, minor accumulation. System is in and out in 12-24 Hours (Sat Daytime Into Early Sun AM). The other side of the spectrum, 12Z EURO, slower evolution, full phase (Low Is Captured-Explosive Development) with a VERY strong low (Sub 970 Low), just offshore of the Mid Atlantic by Sunday. If it verifies, historic winter storm! There is no sense of changing what I have had out the last several days. We won't really know what solution is correct or a solution somewhere in between until at least Thursday, as energy out to the west gets into the better model coverage area. Still thinking at least some accumulating snow (Playing It Conservative). Given what the 12Z EURO shows, we do need to keep in the back of our minds of a more serious event (Historic Snowfall Totals). Not ready to jump onboard the extreme bandwagon yet but it is noted. Need to see other guidance go that way first. As far timing, not changing earlier thinking given the uncertainty. Saturday afternoon and or Saturday night into Sunday. That could shift more to a Sunday into Monday AM deal pending later guidance. Update Wed AM:

ERIC

[earthlight]

I agree with the 00z/21 ECMWF being the best track thus far. Possibly blending in the 12z CMC into the surface low track and intensity. I'd venture to guess the 12z ECMWF is too amplified, while the 12 and 18z GFS/GEFS are too flat.

[masomenos]

It's been a long time but I figure a post here and there is not a bad thing.

From my internal update from earlier this afternoon.

Playing it conservative for now.

-

Great to see you back!

I missed reading your discussions last winter!

[Voyager]

The NWS offices have a number of great discussions this evening ("must read" IMO) that highlight the significant uncertainty that still exists.

Adding CTP into the mix. They too are leaning more toward a Euro solution, but aren't totally discounting the others.

.LONG TERM /THURSDAY THROUGH TUESDAY/...

STILL WATCHING THE POTENTIAL NOREASTER FOR THE HOLIDAY WEEKEND

AND COMPUTER MODELS CONTINUE TO SEND MIXED MESSAGES WITH LARGE

SPREADS IN SOLUTIONS BETWEEN MODELS AND ALSO WITHIN SPECIFIC

ENSEMBLE SUITES AS WELL. SO MAIN MESSAGE IS THAT PLENTY OF

UNCERTAINTY REMAINS IN THIS FORECAST...WHICH SHOULD BEGIN TO SHAKE

OUT IN THE COMING DAYS. YOU CAN MONITOR UPDATES ON THIS POTENTIAL

HIGH IMPACT EVENT IN THE HAZARDOUS WEATHER OUTLOOK /PHLHWOCTP/.

SURFACE LOW STILL PROGGED TO RAPIDLY DEVELOP NEAR THE THE MID-

ATLANTIC COAST - AND TIMING LOOKING A BIT SLOWER NOW AS IT SLIDES

INTO SAT NIGHT OR SUNDAY. GFS REMAINS FASTER WITH PROGRESSION

WHILE ECMWF DEVELOPS A SIG LOW BY THE TIME IT REACHES THE JERSEY

COAST. NEITHER MODEL APPEARS TO GIVE MUCH GROUND WITH THE 12Z

RUNS...AND THESE SOLUTIONS PRODUCE SIG DIFFERENT WEATHER FOR PA.

AS STATED YESTERDAY...MODELS LIKELY HAVING TROUBLE RESOLVING PARENT

UPPER DISTURBANCE /ABOUT TO COME ONSHORE ON THE WEST COAST/ THAT

WILL PLAY LARGE ROLE IN EVENTUAL EVOLUTION ON THE EAST COAST.

HPC PREFERS THE ECMWF DUE TO ITS SLOWER SOLUTION AND MORE

CLIMATOLOGICAL LOW TRACK ALONG THE WESTERN EDGE OF THE WARM WATERS

ASSOCIATED WITH THE GULF STREAM. THIS IS HOW OUR FORECAST WAS

LEANING ALREADY...SO THERE SHOULD BE NO SURPRISES AND NO BIG

CHANGES IN THIS GRIDDED FORECAST PACKAGE. HIGHEST POPS REMAIN OVER

EASTERN SXNS CLOSEST TO THE MEAN STORM TRACK FROM CHRISTMAS NIGHT

SUN AND MON. UNTIL A CONVERGENCE OF SOLUTIONS IS EVIDENT IN THE

DATA...EXPERIENCE FAVORS REFRAINING FROM PICKING SINGLE MODELS/RUNS.

THERE IS STILL PLENTY OF TIME TO REFINE THE FORECAST AS THE

DETAILS BECOME CLEARER AT SHORTER LEAD TIMES.

[LVblizzard]

21z SREFs are out and I don't see much change from 15z, except the ridge axis is a little farther west.