12Z Guidance Discussion 12/21/10

[Ed Lizard]

Any idea in a winter airmass how a 70 to 80 knot 850 mb jet mixes down to the surface, sustained and gusts?

What Eastern New England would lose out as far as snow with a stiff onshore wind, would they make up in significant coastal flooding?

[Organizing Low]

When it came to storms last year (or any previous years really) was the Euro ever this consistent in showing a massive bomb this many runs in this time frame? And was it usually correct?

Basically, I don't remember the Euro ever showing such a massive bomb like this over and over. And I hope that is an indication that this could really happen.

to put things in perspective...

in february 2009, all the models showed a 93-esque Superbomb on day 10, day 9, day 8, day 7, day 6.....talking the lowest was a 958mb on the DGEX but all models had it in the 960s, an Apps runner or slight variant.

all the models.....Euro/Ukie/GFS/GGEM/Nogaps/DGEX/JMA......every single run had it. for those 4 straight days.

in the end, there was no storm....anywhere.

[Terpeast]

Yes, the immediate coast might mix or change over to rain briefly until the storm draws the cold air offshore. But look at that THING... holy cow.

Any idea in a winter airmass how a 70 to 80 knot 850 mb jet mixes down to the surface, sustained and gusts?

What Eastern New England would lose out as far as snow with a stiff onshore wind, would they make up in significant coastal flooding?

[Absolute Humidity]

to put things in perspective...

in february 2009, all the models showed a 93-esque Superbomb on day 10, day 9, day 8, day 7, day 6.....talking the lowest was a 958mb on the DGEX but all models had it in the 960s, an Apps runner or slight variant.

all the models.....Euro/Ukie/GFS/GGEM/Nogaps/DGEX/JMA......every single run had it. for those 4 straight days.

in the end, there was no storm....anywhere.

Not true, that one setup Philly and south/central Jersey with a decient Norlun trought like feature with the primary 400 miles off shore Phillly bagged 8" out of that one, was their biggy snow fall that year.

[Paweatherguy1]

to put things in perspective...

in february 2009, all the models showed a 93-esque Superbomb on day 10, day 9, day 8, day 7, day 6.....talking the lowest was a 958mb on the DGEX but all models had it in the 960s, an Apps runner or slight variant.

all the models.....Euro/Ukie/GFS/GGEM/Nogaps/DGEX/JMA......every single run had it. for those 4 straight days.

in the end, there was no storm....anywhere.

God, yes, I remember that....was supposed to be the snowstorm of the century here. Blizzard, cold, long duration...I remember DT went into full alert mode, and that Henry Margusity went off the total deep end. That is the storm that caused Henry to say he was quitting his blog because of so many personal attacks, and while I agree the personal attacks were bad, when the storm went away off the models, and Henry kept saying it would happen because a volcano was causing sampling issues, well, he didn't help himself.

But yes, the lesson is not to get excited by this sort of thing, because more often than not these sorts of bombs are fantasy.

[Paweatherguy1]

Not true, that one setup Philly and south/central Jersey with a decient Norlun trought like feature with the primary 400 miles off shore Phillly bagged 8" out of that one, was their biggy snow fall that year.

Yeah, but the point was it wasn't a megabomb storm....was nothing like what the system was modeled as in the medium range.

[ArtRosen]

Any idea in a winter airmass how a 70 to 80 knot 850 mb jet mixes down to the surface, sustained and gusts?

What Eastern New England would lose out as far as snow with a stiff onshore wind, would they make up in significant coastal flooding?

Is THAT what the EURO is showing for Monday??? I haven't seen something look like that since the Superstorm of 1993!!!

[dg12x]

I may be off looking at my grainy maps, but judging by precip fields only, ECMWF ensembles look only slightly east of the OP run.

Member 1 of the ensemble package is a crushing hit, essentially mirroring the OP run.

[WhiteoutWX]

I may be off looking at my grainy maps, but judging by precip fields only, ECMWF ensembles look only slightly east of the OP run.

Member 1 of the ensemble package is a crushing hit, essentially mirroring the OP run.

Wow thats very impressive agreement then from this range.

[Organizing Low]

Not true, that one setup Philly and south/central Jersey with a decient Norlun trought like feature with the primary 400 miles off shore Phillly bagged 8" out of that one, was their biggy snow fall that year.

fair enough, but a norlun is hardly a 958 low.

[donsutherland1]

to put things in perspective...

in february 2009, all the models showed a 93-esque Superbomb on day 10, day 9, day 8, day 7, day 6.....talking the lowest was a 958mb on the DGEX but all models had it in the 960s, an Apps runner or slight variant.

all the models.....Euro/Ukie/GFS/GGEM/Nogaps/DGEX/JMA......every single run had it. for those 4 straight days.

in the end, there was no storm....anywhere.

Who will ever forget the Great Non-Storm of February 2009.

[dg12x]

Wow thats very impressive agreement then from this range.

The overall QPF is toned down, which is to be expected from an ensemble mean.

[Ridingtime]

God, yes, I remember that....was supposed to be the snowstorm of the century here. Blizzard, cold, long duration...I remember DT went into full alert mode, and that Henry Margusity went off the total deep end. That is the storm that caused Henry to say he was quitting his blog because of so many personal attacks, and while I agree the personal attacks were bad, when the storm went away off the models, and Henry kept saying it would happen because a volcano was causing sampling issues, well, he didn't help himself.

But yes, the lesson is not to get excited by this sort of thing, because more often than not these sorts of bombs are fantasy.

I'm vaguely starting to remember that. If I recall everyone thought then that 09-10 winter would be the worst ever (putting the Dec. 19th storm aside) and then the rest of February happened, and we all know how things ended.

[yoda]

Updated afternoon disco from HPC

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

302 PM EST TUE DEC 21 2010

VALID 12Z FRI DEC 24 2010 - 12Z TUE DEC 28 2010

...CONTINUED WET ACROSS THE PACIFIC NORTHWEST...

...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

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

[dg12x]

What does it show as it crosses thru the south? farther north? west? thanks.

Really don't want to guess on that as I'm purely looking at temp/precip maps. Hopefully, someone else with greater access can chime in soon.

[Baroclinic Zone]

For SNE the 12z Euro Ensm. came in a hair SE of the 00z run.

[tombo82685]

Really don't want to guess on that as I'm purely looking at temp/precip maps. Hopefully, someone else with greater access can chime in soon.

the euro ens on allans site come out in 15 mins

[dg12x]

For SNE the 12z Euro Ensm. came in a hair SE of the 00z run.

Cool...that confirms what I saw...thanks.

[yoda]

Also from 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

[Organizing Low]

Who will ever forget the Great Non-Storm of February 2009.

what is funny about that storm for me Don,

is that ever since, i never mention any storm to any of my friends or relatives unless it is within 100 hours. before that, i always used to..... but ever since, my mouth is zippered shut even as TV/radio folks mention things and the hype gets out.....i just sit quietly. its a rule i made after that debacle.

and its already worked out beautifully yet again with the past 2 events already this winter. i have the great NonStorm to thank for that everytime, and i come off looking like a genius.

the utter total and catastrophic failure of the models that February.....not a lesson i will soon forget.

[CoastalWx]

For the MA peeps, at hr 120, the EC ensembles have the slow maybe 50 miles ese of ILM vs east of ORF and tucking closer to the coast at 00z. It then moves to a position maybe 150-200 miles east of Delmarva, but again some spread develops based on large 998mb isobar. From there it moves nne passing near or perhaps just east of 40/70 but again there exists some spread. This solution is slower than 00z.

[Organizing Low]

For the MA peeps, at hr 120, the EC ensembles have the slow maybe 50 miles ese of ILM vs east of ORF and tucking closer to the coast at 00z. It then moves to a position maybe 150-200 miles east of Delmarva, but again some spread develops based on large 998mb isobar. From there it moves nne passing near or perhaps just east of 40/70 but again there exists some spread. This solution is slower than 00z.

intriguing.

thanks for the update!

[Paweatherguy1]

what is funny about that storm for me Don,

is that ever since, i never mention any storm to any of my friends or relatives unless it is within 100 hours. before that, i always used to..... but ever since, my mouth is zippered shut even as TV/radio folks mention things and the hype gets out.....i just sit quietly. its a rule i made after that debacle.

and its already worked out beautifully yet again with the past 2 events already this winter. i have the great NonStorm to thank for that everytime, and i come off looking like a genius.

the utter total and catastrophic failure of the models that February.....not a lesson i will soon forget.

I remember showing off DT's discussion, of comparisons to the 1950 App's superbomb....I should have just shut up and watched what happened, but I was never as excited about a storm as that one.

[CoastalWx]

144 Euro ensemble mean. WOW!!

That's not the ensemble.

[CoastalWx]

How about as the low comes thru the south? Farther north? south? Thanks

It's maybe a hair flatter and further south. To me, it seems like the nrn stream isn't as strong as the 00z run was, but I think srn stream impulse is actually a little stronger this time around. It basically equates to a slightly later phasing imo.

[NorthShoreWx]

For the MA peeps, at hr 120, the EC ensembles have the slow maybe 50 miles ese of ILM vs east of ORF and tucking closer to the coast at 00z. It then moves to a position maybe 150-200 miles east of Delmarva, but again some spread develops based on large 998mb isobar. From there it moves nne passing near or perhaps just east of 40/70 but again there exists some spread. This solution is slower than 00z.

Sounds like the euro ens mean doesn't have the mixing issues that the op would have for eastern areas.

For Don S, in response to the Feb 2009 question:

[weathervswife]

That's not the ensemble.

Yep, wrong link. It's not out yet. I deleted. Thanks.

[Weather Czar]

It's maybe a hair flatter and further south. To me, it seems like the nrn stream isn't as strong as the 00z run was, but I think srn stream impulse is actually a little stronger this time around. It basically equates to a slightly later phasing imo.

Thanks for the response.

[donsutherland1]

what is funny about that storm for me Don,

is that ever since, i never mention any storm to any of my friends or relatives unless it is within 100 hours. before that, i always used to..... but ever since, my mouth is zippered shut even as TV/radio folks mention things and the hype gets out.....i just sit quietly. its a rule i made after that debacle.

and its already worked out beautifully yet again with the past 2 events already this winter. i have the great NonStorm to thank for that everytime, and i come off looking like a genius.

the utter total and catastrophic failure of the models that February.....not a lesson i will soon forget.

That's a good approach. I tend to err on the side of conservatism with possible events unless they are relatively high confidence (i.e., some of last winter's threats with an active subtropical jet and strong blocking).

[goldstar]

That's not the ensemble.

Is this scenario possible with the western ridge in that weird spot?