Christmas Storm IV

[Lookout]

Updated HPC, they are just as uncertain as the rest of us. Good discussion though.

PRELIMINARY EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

859 AM EST WED DEC 22 2010

VALID 12Z SUN DEC 26 2010 - 12Z WED DEC 29 2010

...HIGH UNCERTAINTY WITH TRACK/IMPACT OF POWERFUL EAST

COAST/WESTERN ATLANTIC STORM SUN-MON...

AN AMPLIFIED ERN PAC TROF AND SHARPENING W-CNTRL NOAM RIDGE IN

PLACE AT THE START OF THE MEDIUM RANGE PERIOD EARLY SAT WILL

SUPPORT FURTHER DEEPENING OF AN EVOLVING ERN CONUS TROF THAT

SHOULD REACH THE EAST COAST AROUND DAY 5 MON. UPSTREAM FLOW

SHOULD TREND FLATTER WITH TIME AS ERN PAC TROF ENERGY LIFTS NEWD

INTO THE WEST BY SUN-MON AND CONTINUE EWD THEREAFTER... WHILE

ADDITIONAL ERN PAC ENERGY WITH GENERALLY MODEST AMPLITUDE

CONTINUES TOWARD/INTO THE WEST. THIS LOWER AMPLITUDE WRN FLOW IS

EXPECTED TO KICK OUT THE DEEP ERN TROF BY TUE-WED.

OPERATIONAL MODELS AND ENSEMBLES CONTINUE TO SHOW CONSIDERABLE

SPREAD WITH THE TRACK OF THE SYSTEM FCST TO DEEPEN AS IT TRACKS

FROM THE GULF COAST OR GULF OF MEXICO INTO THE WRN ATLC OR ALONG

THE EAST COAST. THE PAST 2-3 OPERATIONAL ECMWF RUNS HAVE

INDICATED A MASSIVE...DEEP...SLOW-MOVING CYCLONE HUGGING THE

CAROLINA AND MID ATLANTIC COASTS THE TWO DAYS FOLLOWING CHRISTMAS.

THE ECMWF AND UKMET WERE THE FIRST OF THE GLOBAL MODELS TO SWITCH

FROM TRACKING THIS WAVE ALONG 40N THROUGH THE MIDWEST...TO A

SUPPRESSED PATH ACROSS THE DEEP SOUTH. SINCE THIS ADJUSTMENT...

THE UKMET TRENDED EVEN FARTHER SOUTH...WITH THE ECMWF LOCKING ONTO

AN EVOLUTION THAT TAKES THE DEVELOPING LOW TO THE FLORIDA

PANHANDLE AND THEN SHARPLY UP THE EASTERN SEABOARD. THE 06Z GFS

HAS ALSO TRENDED TO A VERY SUPPRESSED SOLN ACROSS THE GULF...

ADDING SUPPORT FOR SUCH A SCENARIO FOR AT LEAST THAT PART OF THE

FCST.

THE TRACK OF THIS SYSTEM BEYOND THE GULF REGION STILL DEPENDS

HEAVILY ON SHRTWV DETAILS OF NRN STREAM FLOW... WITH WHICH MODELS

SOMETIMES HAVE CONSIDERABLE DIFFICULTY UNTIL WITHIN A COUPLE DAYS

OF THE VALID TIME. OF PARTICULAR NOTE THE 00Z/06Z GFS ARE ON THE

SHARP/WWD ELONGATED SIDE OF THE FULL GUIDANCE SPREAD WITH ENERGY

OVER THE WRN GRTLKS/UPR MS VLY AS OF EARLY DAY 4 SUN. THIS

ORIENTATION OF FLOW LIKELY PLAYS A PART IN THOSE GFS RUNS TRACKING

THE DEEPENING WRN ATLC SFC LOW WELL OFF THE COAST. THE 00Z

GEFS/ECMWF ENSEMBLE MEANS OFFER MORE SUPPORT FOR A SHARPER AND

MORE N-S ORIENTED TROF THAN RECENT GFS RUNS. WHILE THE 00Z AND

12Z/21 ECMWF EVOLUTIONS ARE FAIRLY EXTREME WITH THE DEPTH OF THE

MID LVL LOW THAT CLOSES OFF NEAR THE EAST COAST... THEY APPEAR A

LITTLE MORE COMPATIBLE WITH ENSEMBLE MEAN IDEAS VERSUS GFS RUNS.

AS THE LOW TRACKS ALONG THE EAST COAST THE 00Z ECMWF IS ON THE WRN

SIDE OF THE SPREAD OF 00Z ECMWF ENSEMBLE MEMBERS AND WWD OF ALL

00Z GEFS MEMBERS WHICH ARE ADMITTEDLY SOMEWHAT LOWER IN

RESOLUTION. WHILE THE STRONG DYNAMICS ALOFT MAY WELL SUPPORT THE

OPERATIONAL ECMWF SOLN... IT IS TOO EARLY TO SUBSCRIBE FULLY TO

ITS FCST. A SOLN IN THE WRN HALF OF THE GUIDANCE SPREAD STILL

APPEARS REASONABLE THOUGH. AS A RESULT WILL GO WITH A BLEND

CONSISTING OF 30 PCT EACH 00Z ECMWF AND 12Z/21 ECMWF RUNS WITH THE

REMAINING 40 PCT OCCUPIED BY THE 00Z ECMWF ENSEMBLE MEAN.

THE PREFERRED BLEND FOR THE ERN CONUS/WRN ATLC EVOLUTION TONES

DOWN THE 00Z ECMWF THAT IS ON THE SHARP/AMPLIFIED SIDE OF THE

ENVELOPE WITH THE MID LVL TROF ENTERING THE WEST ON DAY 4 SUN.

CONFIDENCE IN PARTICULARS OF ERN PAC TO PLAINS/GRTLKS FLOW

DECREASES AS AMPLITUDE OF THE MEAN FLOW LIKEWISE DECREASES. BY

DAY 7 WED THE MOST COMMON IDEAS OF ENSEMBLE MEANS ARE TOWARD A

WEAK SHRTWV REACHING THE GRTLKS AND VICINITY... A SHRTWV TROF

NEARING THE WEST COAST... AND A MODERATE TROF REACHING NWRN

MEXICO. ECMWF RUNS FIT THE ENSEMBLE MEANS BETTER THAN THE 00Z/06Z

GFS WHICH APPEAR SOME WHAT SLOW. EXPECT SOME LOCALLY MDT-HVY PCPN

OVER CNTRL-NRN CA DURING THE FIRST HALF OF THE PERIOD WITH THE

LEADING TROF EJECTING INTO THE WEST. EXPECT A DRIER PERIOD ALONG

THE SRN HALF OF THE WEST COAST MON-TUE... BUT THE DAY 7 SHRTWV MAY

PUSH PCPN SWD AGAIN BY NEXT WED.

RAUSCH/CISCO

[GreensboroWx]

Ignore the qpf right now....it's the big players on the field and phasing which are MUCH more important. With this kind of phasing and energy, moisture transport will not be a problem.

looks decent, still i think it lacks moisture, especially for the strength and magnitude of this storm...

[downeastnc]

Damn...we need this baby to phase earlier. Let the nail biting begin. Wildre...this is only Weds. Please do not make some poor weenie have thoughts of suicide.

Well some of us dont......a later phase is better for the masses than a early phase, early phase would mean rain for us, or at best snow changing to rain. Where as a later phase would mean snow for everyone granted out west and Ga, your totals might not be as high as they would on a earlier phase but you would all get accumulating snow as would we here in the east.

[eyewall]

My update today is late because of work and I am also awaiting the 12z GFS run.

[NCStateMMY]

Do any of the models take into account the baroclinicity between the Gulf Stream and the SE coast? I think that is going to be a major factor if and when this thing bombs out off the coast.

[Shawn]

NOGAPS is pretty potent with the shortwave through 60. I know, the model's not that great but still. Eagerly awaiting the GGEM/UKMET for TRENDS!

[Rankin5150]

looks decent, still i think it lacks moisture, especially for the strength and magnitude of this storm...

Welcome. The initial way of precip into NC will most likely be underdone. Like Robert (Foothills) has been alluding too, the dynamics of this system are incredible. All in all, keep the expectations on the low end. The chance of this being a huge snowmaker are still greenlight IMHO.

[WidreMann]

Remember also that with the cold air in place and feeding in from that high, we'll probably get better ratios than usual. So having QPF in the 0.10" to 0.25" range could produce 2-5" of snow for some folks. I don't think anyone in this thread would be unhappy with 2-5" of snow on Christmas or the day after.

[WidreMann]

My update today is late because of work and I am also awaiting the 12z GFS run.

The GFS is already out, dude.

[CaryWx]

What we really need is the next EURO to hold it's same prediction course. Plain and simple. That would satiate me for the time being. The GFS hopefully is just slow in getting it.

[kanc2001]

Ignore the qpf right now....it's the big players on the field and phasing which are MUCH more important. With this kind of phasing and energy, moisture transport will not be a problem.

exactly, sounds to me like we are very much still in the game and that we are trending toward a GFS/Euro blend or maybe a full consensus??

[WidreMann]

What we really need is the next EURO to hold it's same prediction course. Plain and simple. That would satiate me for the time being. The GFS hopefully is just slow in getting it.

Wouldn't it be funny if just as the GFS is getting it, the Euro gives it up?

[eyewall]

The GFS is already out, dude.

Thank you I am aware of this but on the site I use it is at 90 hours and I like the resolution of their graphics for analysis.

[GreensboroWx]

The GFS run simply gives me more confidence that the EURO may be right or more correct than the others.....I'm curious to see what the GFS ensembles show.....

[Shawn]

If our local offices see the Euro's operational come in the same or even dare I say.. stronger.. and see the GFS trends... I think we are gonna see a lot of collaboration between the offices soon.

[beanskip]

Yeah -- we didn't need the GFS to hit a home run, just foul off a few pitches and stay alive. I tell you what, when the GFS was out to about 36 hours, the mojo in this thread was ebbing. Now, feels like we're back!

The GFS run simply gives me more confidence that the EURO may be right or more correct than the others.....I'm curious to see what the GFS ensembles show.....

[nchighcountrywx]

Could one of our better professional mets discuss why the GFS is very light on QPF as compared to the ECMWF?

If taken literally, all of the GFS QPF is East of I-95 with the big snows lined up even further east.

A 1989 NC White Christmas type event.

[Shawn]

Could one of our better professional mets discuss why the GFS is very light on QPF as compared to the ECMWF?

If taken literally, all of the GFS QPF is East of I-95 with the big snows lined up even further east.

A 1989 NC White Christmas type event.

Im not a met, but it misses the perfect phase.. therefore not hugging the coast/as amplified of a system I'd think.

[strongwxnc]

Tale of the state. In WNC (southern foothills) Im with Rankin on that one. I hope the solution makes all.

Well some of us dont......a later phase is better for the masses than a early phase, early phase would mean rain for us, or at best snow changing to rain. Where as a later phase would mean snow for everyone granted out west and Ga, your totals might not be as high as they would on a earlier phase but you would all get accumulating snow as would we here in the east.

Glad you are posting for this storm. Your thoughts are greatly welcomed!!!

The GFS run simply gives me more confidence that the EURO may be right or more correct than the others.....I'm curious to see what the GFS ensembles show.....

[kanc2001]

KILM starting to warm up to the idea.....

.LONG TERM /SATURDAY THROUGH TUESDAY/...

AS OF 3 AM WEDNESDAY...NOT MAKING A LOT OF CHANGES TO LONG TERM

PERIOD. GUIDANCE CONTINUES TO SLOW DOWN SYSTEM EMERGING FROM THE

SOUTHWEST. IN ADDITION GUIDANCE HAS CONTINUED THE TREND OF A

SLOWER/DEEPER SYSTEM AFFECTING THE SOUTHEAST LATE DURING THE HOLIDAY

WEEKEND. GFS REMAINS THE FASTEST WITH ECMWF THE SLOWEST. LOWERED

POPS FOR SAT AND EXTENDED CHC POPS THROUGH SAT NIGHT INTO SUN. DID

NOT YET ADD ANY FROZEN PRECIP GIVEN THE LARGE AMOUNT OF UNCERTAINTY

WITH RESPECT TO TIMING AND TRACK...BUT AT THE VERY LEAST IT IS

STARTING TO LOOK LIKE SNOW MAY BE AN ISSUE AS THE STORM EXITS ON SUN.

AFTER THE STORM EXITS ANOTHER ARCTIC AIR MASS WILL BE PUSHED INTO

THE DEEP SOUTH BY LARGE 5H TROF. DRY ARCTIC AIR ENSURES NO CLOUDS OR

PRECIP MON AND TUE BUT WILL ALSO KEEP TEMPERATURES BELOW TO WELL

BELOW CLIMO. EXTENDED MOS NUMBERS AREA RIGHT AROUND 40 AND LIKELY

BIAS IN FAVOR OF CLIMO...SUGGESTING HIGHS IN THE MID TO UPPER 30S

AND LOWS IN THE TEENS.

EDIT: just realized this was their 3am, my bad because they just updated the short term at 11:30am

[kanc2001]

Could one of our better professional mets discuss why the GFS is very light on QPF as compared to the ECMWF?

If taken literally, all of the GFS QPF is East of I-95 with the big snows lined up even further east.

A 1989 NC White Christmas type event.

implies a slider I imagine, not a phase

[Ivanhater]

Wow..NWS Mobile/Pensacola is biting!

...A RARE WINTRY WEATHER PRECIPITATION EVENT POSSIBLE OVER THE INTERIOR

GULF COAST LATE CHRISTMAS DAY...

A WARM FRONT LOOKS TO HUG THE COAST WITH LOW PRESSURE TRACKING

EASTWARD OVER THE COASTAL WATERS. A TIGHT GRADIENT IN TEMPERATURE

WILL EXIST WITH THE COLDER TEMPERATURES OVER THE INTERIOR. THE LOW

IS PROGGED TO PULL COLDER AIR SOUTHWARD DURING THE DAY AND MOISTURE

FLOWING ATOP THE COLDER DOME MAY RESULT IN SOME SNOW MIXING IN WITH

THE RAIN OVER THE FAR NORTHERN ZONES LATE IN THE DAY SAT. THIS IS

SUPPORTED BE AN ASSESSMENT OF CRITICAL WINTER WEATHER THICKNESSES AND

FORECAST SOUNDINGS WHICH SHOW THERMAL PROFILES JUST OFF THE SURFACE

GOING BLO ZERO CELSIUS THERE BY EVENING. NEAR THE WARM FRONT...DAYTIME

HIGHS LOOK TO OCCUR EARLIER IN THE DAY WITH A COLD RAIN AND FALLING

TEMPERATURES EXPECTED INTO THE AFTN. AFTER SUNSET SAT...THE FORECAST

THERMAL PROFILES LOOK TO SUPPORT A MENTION OF LIGHT SNOW NORTH OF THE

IMMEDIATE COAST AS WRAP AROUND MOISTURE WEST OF THE DEPARTING AND

STRENGTHENING LOW SLIDES EASTWARD THROUGH THE AREA. STILL TOO EARLY

TO OFFER SPECIFICS ON ACCUMULATION POTENTIAL AS ALL OF THIS IS HIGHLY

DEPENDENT ON STRENGTH AND TRACK OF THE LOW. STAY TUNED.

[snowlover91]

Sry

The mods hve warned against posting short one word or phrases on the forum.. They are cracking down on it so be careful with posts like this.

As a side note, the 12z gfs looks very good to me. It appears to be playing catch up with the euro, tonights 00z runs will be key as the data will be onshore and in the models tonight. Can't wait to see what the euro has to say. Also of note, the nogaps suppressed it to oblivion last night but today looks much better.

[tnweathernut]

i am stepping to the ledge here in northeast TN. Everything is going away from a snow here (outside the Euro). The area of overrunning/streaking precip that was going to be my worst case scenerio to squeeze out an inch or so is going POOF too. Not feeling good at all on the west side of the apps.....maybe the 12z Euro will keep me from stepping off.

[Shawn]

i am stepping to the ledge here in northeast TN. Everything is going away from a snow here (outside the Euro). The area of overrunning/streaking precip that was going to be my worst case scenerio to squeeze out an inch or so is going POOF too. Not feeling good at all on the west side of the apps.....maybe the 12z Euro will keep me from stepping off.

If the EURO verified, you'd have snow.

[FoothillsNC]

Can anyone see the pressure the GFS has at 126? It appears to be close to 960mb or so, Its extreme. I still like the extreme solution and have little doubt that it plays out for someone. We have historic blocking ,a split flow, an extreme PNA ridge at just the right time, the incredibly deep Newfoundland vortex , and it pulls away at precisely the right time (on euro), so theres no reason why we shouldn't have an extreme event. Its literally how they're made. Normally this setup occurs in New England though, not the Southeast, so thats why everyone has questions. Its still uncertain exactly wher the phase occurs and that is the decider on where the storm goes, but I have very little doubt really on this storm getting into record deep territory , as its about the perfect storm setup. We could end up with a 990 or less storm on the Georgia coast, which to me is pretty iincredible, and watch it go from that to 975 when its aproaching Wilmington or the Outer Banks, which would be a sight to behold....with blizzard conditions pretty far inland.

As long as the northern stream is diving due south like the Euro (and now the GFS) in the lower Miss. Valley then our southern system should begin to really amplify and quite honestly, the sky's the limit on what happens to its pressure. It could be March 1993, but further east for all practical purposes.

[Rob]

What I do not understand is that 700RH are very well here in Middle Tennessee. You would think that QPF would reflect this over our area.

[Weather Czar]

CMC at 60 hours.

http://www.weatheroffice.gc.ca/data/model_forecast/colour_images/12_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_060.jpg

[NavarreDon]

Foot, Could you give your thoughts on the Mnts. if you have time? I am no expert but it seems like they may be to far north and then to far west. I know the ratios will be in play here as will the flow but feel like they may get left out of the big dance. Thanks in Advance.

[Lee]

i am stepping to the ledge here in northeast TN. Everything is going away from a snow here (outside the Euro). The area of overrunning/streaking precip that was going to be my worst case scenerio to squeeze out an inch or so is going POOF too. Not feeling good at all on the west side of the apps.....maybe the 12z Euro will keep me from stepping off.

Well, feeling somewhat down over here too. However, IF, the SE bias come thru with the GFS, then expect this area to fill in in future runs and come inline with the euro. A northerly flow along with some wraparound moisture from the storm itself should still produce some decent upslope. Unfortunately, prob. not by Christmas morn. way it looks now.

We really need that Low to bomb much sooner , say, over the gulf just south of Orleans, and then be able to throw more moisture north and maybe also probably more apt to track further west.

If the aforementioned fails, back this way at least, the northern branch feature still may hold together enough for some accs Christmas morning.