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The Big One - Forecast & Discussion

Wow

By Wow,
in Southeastern States

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BullCityWx

BullCityWx

Posted
Posted

Sounding for me at 36 was +0.9 at 900mb during peak precip rates so it did sneak it in briefly.

 

huh. 

 

Date: 36 hour Eta valid 0Z THU 13 FEB 14
Station: KCLT
Latitude: 35.22
Longitude: -80.93
-------------------------------------------------------------------------------
LEV PRES HGHT TEMP DEWP RH DD WETB DIR SPD THETA THE-V THE-W THE-E W
mb m C C % C C deg knt K K K K g/kg
-------------------------------------------------------------------------------
0 1000 150
SFC 992 210 -3.9 -4.9 93 1.0 -4.2 18 13 269.9 270.3 269.4 277.1 2.68
2 950 553 -6.9 -6.9 100 0.1 -6.9 26 26 270.2 270.6 269.1 276.7 2.39
3 900 979 -1.5 -1.7 99 0.2 -1.6 73 32 279.9 280.6 276.9 290.4 3.76
4 850 1436 0.2 0.2 100 0.0 0.1 108 27 286.3 287.1 281.0 299.2 4.55
5 800 1922 -0.1 -0.1 100 0.0 -0.2 129 16 291.0 291.9 283.3 304.7 4.73
6 750 2439 -1.7 -1.7 100 0.0 -1.7 135 37 294.8 295.6 284.6 308.0 4.51
7 700 2986 -3.4 -3.4 100 0.0 -3.4 183 31 298.8 299.5 285.9 311.5 4.26
8 650 3570 -6.0 -6.3 97 0.4 -6.1 201 35 302.2 302.9 286.5 313.4 3.66
9 600 4195 -8.2 -8.7 96 0.5 -8.4 218 33 306.7 307.3 287.8 317.0 3.30
10 550 4866 -12.8 -17.2 70 4.4 -14.1 231 34 308.9 309.2 287.0 314.7 1.81
11 500 5584 -18.2 -24.0 61 5.7 -19.6 240 44 310.8 311.0 286.9 314.5 1.10
12 450 6363 -23.2 -28.3 63 5.1 -24.2 233 58 314.0 314.2 287.7 316.8 0.82
13 400 7215 -28.8 -31.4 78 2.6 -29.2 213 61 317.5 317.6 288.7 319.9 0.69
14 350 8155 -36.2 -39.1 74 3.0 -36.5 214 75 320.0 320.0 289.2 321.3 0.37
15 300 9205 -45.3 -48.5 70 3.2 -45.5 213 81 321.5 321.5 289.4 322.0 0.16
16 250 10394 -55.6 -58.8 68 3.1 -55.7 222 105 323.4 323.4 289.9 323.6 0.06
17 200 11783 -63.0 -69.9 39 6.9 -63.1 230 128 333.0 333.0 292.6 333.1 0.02
18 150 13556 -60.6 -74.7 14 14.0 -60.8 246 101 365.6 365.6 299.8 365.7 0.01
19 100 16085 -60.9 -81.9 5 21.0 -61.2 240 54 410.1 410.1 306.5 410.1 0.00
TRP 0
WND 0
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SnowNiner

SnowNiner

Posted
Posted

The low is tracking off shore, there's very well established deep CAD sig... it's not switching over to sleet all the way back into Hickory.  Climo for this track says the sleet stays S and E of 85.  Euro looks perfect wrt to temp profiles.

 

I agree, we're on the same page here.  I'm just a weenie, but this overall set up screams heavy snow CLT and GSO west.  Hopefully the trends continue and more models jump on board. 

 

GSP ticked up my totals from 4-8 to 5-9 just a few minutes ago.  I think that continues.  (please, please please :unsure: )

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MotoWeatherman

MotoWeatherman

Posted
Posted

RGEM is looking much deeper than the NAM, which probably means this run can be tossed. Good.

 

The RGEM picked up on the intensity up here in NGA for todays event at on 0z last nights run.. Much better than NAM or GFS.  Precip still looks bonker with nice comma warp Wednesday night. 

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phil882

phil882

Posted
Posted

If the Euro does verify airports up and down the eastern seaboard could be shut down. This storm could end up having a major economic impact! 

 

This... this is looking more and more like a KU snowstorm. Euro ensembles are in very good agreement on this outcome now.

 

Something about the thermal fields on the NAM just aren't right...IMO  Heck we are busting by 3 degrees already

 

 

The Nam and Gfs have been terrible for here with today's event. It has been snowing since 5:00am. Although they may be correct on our dusting total of snow the QPF projection wasn't even close nor where the temp profiles.

 

 

I'm going to get on my high horse for a brief moment, but I think the GFS and NAM are doing a horrible job with this event  (wednesday and beyond). When I look at models and try to get an assessment of what is going to happen, the first thing I do is look at the ECMWF and its ensembles.

 

When the ECMWF is showing an overamplified solution relative to the rest of the guidance, I stand back and try to understand if its catching on to something the other models are missing or if its an outlier that should be thrown out. The easiest way to figure this is out is to look at the its ensemble mean. Guess what, the ECMWF ensemble mean is pretty much exactly what the deterministic solution is. The ECMWF Ensemble Prediction System (EPS) is superior to the GFS Ensembles because it contains 50 members and does a more realistic job of depicting the probability PDF of any one particular solution, preventing it from being under dispersive like the GFS ensembles are in most cases.

 

So when there is strong agreement within 72 hours from the ECMWF and the ECMWF ensembles, I place that in the highest regard over all other guidance. Thats what we are seeing currently. The GFS and NAM are completely on the edge of the ECMWF ensemble PDF and therefore should both be considered outliers in this case. Its a little startling to see this must dispersion between the model guidance within 72 hours, but for tricky phasing cases like this, its the norm. While taking a mean might sound like the best course of action, in reality when there is this much spread, you are taking a good forecast and merging with a bad forecast to create a mediocre forecast. I think it would be a better idea to place greater emphasis on the ECMWF solution given the strong support it has by its ensembles. 

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nchighcountrywx

nchighcountrywx

Posted
Posted

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION

NWS WEATHER PREDICTION CENTER COLLEGE PARK MD

439 AM EST TUE FEB 11 2014

 

VALID 12Z TUE FEB 11 2014 - 12Z FRI FEB 14 2014

 

...SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY TO SOUTHEAST AND UP

EAST COAST...

 

A HIGH SOCIETAL IMPACT WINTER STORM IS IMMINENT ACROSS THE SRN

TIER OF THE COUNTRY AND VERY LIKELY TO PROCEED UP THE EAST COAST

ON WED AND THURS... BASICALLY EXTENDING FROM TX/LA TO NEW ENGLAND.

 

A VERY COMPLEX UPPER PATTERN WITH SPLIT FLOW REGIME ACROSS THE ERN

TWO-THIRDS OF THE COUNTRY... WHILE A MAMMOTH DOME OF SURFACE

ARCTIC HIGH PRESSURE CONSUMES THE ENTIRE REGION AND ESPECIALLY

EAST OF THE APPALACHIANS. AN IMPRESSIVE AND DYNAMIC IMPULSE OVER

THE MID MS VALLEY WILL GLIDE ALONG THE NRN STREAM AND REACH THE

NORTHEAST COAST ON TUES. MEANWHILE... THE LAST SHORT WAVE THAT

IMPACTED THE CENTRAL CA COAST WILL ADVANCE DOWNSTREAM ALONG THE

ACTIVE SRN BRANCH AND TRACK ACROSS TX TO THE LOWER MS VALLEY.

ALREADY MOISTURE IS OVERRUNNING THE QUASI-STATIONARY FRONT NEAR

THE GULF COAST FOR A WELL-ESTABLISHED PRECIP SHIELD ACROSS THE

SOUTH CONTAINING SNOW AND FREEZING RAIN. THIS SHIELD OF MOISTURE

WILL ADVECT DOWNSTREAM DURING THE DAY INTO THE SOUTHEAST OR WITH

THE PACE OF THE NRN STREAM IMPULSE. THIS WILL RESULT IN LOCALLY 1

TO 3 OR 4 INCHES OF SNOW FROM NRN AL/GA THROUGH UPSTATE SC INTO

SERN/ERN NC WITH POSSIBLE .10 TO .50 INCH OF ICING THREAT FROM

NRN/CENTRAL GA THROUGH MUCH OF SC INTO SERN NC AND THE BEGINNING

OF A PARALYZING ICE STORM. AS THE SRN STREAM FEATURE CROSSES TX TO

THE LWR MS VALLEY... SOME SLIGHT AMPLIFICATION WILL OCCUR AS PAC

DYNAMICS NEAR THE NW WILL DIG DOWN THE FRONT RANGE OF THE ROCKIES

INTO THE CENTRAL PLAINS. THUS THE GENERALLY SUPPRESSED PRECIP

SHIELD ACROSS TX/LA WILL BEGIN TO EXPAND AND LIFT ACROSS THE SOUTH

AND TOWARD THE SRN APPALACHIANS... WHILE INDUCING A WAVE OF LOW

PRESSURE NEAR THE CENTRAL GULF COAST. THIS WOULD RESULT IN SOME

LIGHT AND MINIMAL ACCUMULATIONS OF SNOW ACROSS NORTH TX BUT A

DECENT AMOUNT OF ICING FROM THE HILL COUNTRY OF TX THROUGH ERN

TX/MUCH OF LA TO NORTH CENTRAL MS. WPC STAYED VERY CLOSE TO A

COMPROMISE OF THE 00Z GFS... ECMWF AND 21Z/10 SREF MEAN.

 

THE DIGGING UPSTREAM DYNAMICS OVER THE CENTRAL PLAINS WILL RAPIDLY

CATCH UP WITH THE SRN STREAM DYNAMICS TO POTENTIALLY PHASE OVER

THE SERN PORTION OF THE COUNTRY. THIS WILL ALLOW A SIGNIFICANT

INCREASE IN MOISTURE ADVECTION FROM THE GULF OF MEXICO AND

ATLANTIC TO INTERACT WITH A DEVELOPING

COASTAL LOW ALONG THE SOUTHEAST COAST... WHILE ONE OF THE MORE

IMPRESSIVE CONFLUENT ZONES ALOFT KEEPS THE ARCTIC AREA OF HIGH

PRESSURE ENTRENCHED OVER THE EAST. A TRUE BAROCLINIC LEAF PRECIP

SHIELD WILL EVOLVE FEATURING MAJOR ICING FROM ATL TOWARD CAE THEN

SHIFTING NORTH TOWARD RDU AND A VERY HEALTHY DEFORMATION ZONE OF

BANDING SNOWFALL FROM NRN GA/SWRN NC/NWRN SC NEWRD TO SWRN/CENTRAL

VA BEFORE REACHING THE DC/BALT/PHIL METRO AREAS. THE ICE

ACCUMULATIONS REMAIN MIND-BOGGLING IF NOT HISTORICAL WITH

ADDITIONAL .50 TO 1 INCH AXIS FROM ATLANTA-ATHENS-AUGUSTA-COLUMBIA-RDU AND 8

TO 10 INCHES OF SNOW FROM ASHEVILLE/GREENVILLE SPARTANBURG to ROANOAKE/LYNCHBURG to JUST SOUTH OF DC

WITH A POSSIBLE FOOT NEAR SWRN NC/NWRN SC. WPC CONTINUED

THE COMPROMISE OF THE GFS/ECMWF/UKMET WITH SUPPORT FROM THE SREF

MEAN FOR THE BEGINNING OF A CLASSIC EAST COAST WINTER STORM.

 

THEN ON THURS... THE INTENSIFYING SURFACE LOW GOING THROUGH RAPID

CYCLOGENESIS WILL TRACK FROM THE OUTER BANKS OF NC TO THE NEW

ENGLAND COASTLINE. THIS WILL RESULT IN A WEALTH OF ATLANTIC

MOISTURE SURGING INTO THE NRN MID-ATL STATES AND NORTHEAST FOR A

NARROW BUT IMPRESSIVE AXIS OF HEAVY SNOWFALL. THE GUIDANCE IS ALL

UNANIMOUS IN A WELL-ESTABLISHED DEFORMATION AXIS/COMMA HEAD OF

HEAVY SNOW BUT DIFFER ON THE EXACT CORRIDOR. WPC TOOK A MEAN

APPROACH OR TAKING OUT THE SPECIFIC DETAILS AND RESOLUTION OF THE

GUIDANCE FOR A HEAVY SNOW AXIS JUST WEST OF THE I95 CORRIDOR FROM

DC/BALT AREA TO BOS AND CONTINUING UP INTO MAINE. THE EXACT

AMOUNTS ON THURS ARE STILL SOMEWHAT UNCERTAIN BUT A STRIPE OF 6 TO

12 INCHES WILL BE POTENTIALLY POSSIBLE FROM NERN PA/NWRN NJ

THROUGH DOWN EAST MAIN

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phil882

phil882

Posted
Posted

Great post phil and I agree that the Euro has been rock solid on the placement of the low and, while maybe over amped on the QPF, has nailed the track. The GFS will come back to the Euro track IMO and will close off the 5H earlier like the king does.

 

That's what I am expecting... still doesn't quite do it at 12z but is more amplified in the first 24-30 hours. One problem the GFS might have in these cases that are amplified by diabatic heating (and hence mid-level PV production) is that the model applies significant diffusion to dampen out smaller wavenumbers to prevent computational modes from growing exponentially and making the model crash. The negative impact of this increase in diffusion is that it sometimes dampens out important wave signals that could have implications beyond the short range in a forecast. The ECMWF to my knowledge doesn't use the same time differencing scheme so it doesn't need to apply as much diffusion to dampen the computational mode of smaller wavenumbers.

 

Non-techinical version... GFS is more likely to dampen out important features when there is a lot of convection being produced in a model solution (this is not the same as convective feedback since that is more related to a poor cummulus scheme overproducing precipitation in particular regiemes). 

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DixieBlizzard

DixieBlizzard

Posted
Posted

That's what I am expecting... still doesn't quite do it at 12z but is more amplified in the first 24-30 hours. One problem the GFS might have in these cases that are amplified by diabatic heating (and hence mid-level PV production) is that the model applies significant diffusion to dampen out smaller wavenumbers to prevent computational modes from growing exponentially and making the model crash. The negative impact of this increase in diffusion is that it sometimes dampens out important wave signals that could have implications beyond the short range in a forecast. The ECMWF to my knowledge doesn't use the same time differencing scheme so it doesn't need to apply as much diffusion to dampen the computational mode of smaller wavenumbers.

 

Non-techinical version... GFS is more likely to dampen out important features when there is a lot of convection being produced in a model solution (this is not the same as convective feedback since that is more related to a poor cummulus scheme overproducing precipitation in particular regiemes). 

 

You are channeling your inner HM, Phil. Great post!

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packfan98

packfan98

Posted
Posted

So if the intensity of the Euro verifies, the track will be just inland and there will be huge mixing issues far to the west?  I'm a little confused and would love to hear a met's thoughts on the mixing.  I believe that the EURO showe less mixing issues on its last run than other models are showing this morning, even though the track is further to the west.  Was that because the cold air was wrapped in due to the intensity?  Any thoughts on the mixing issue will be greatly appreciated by many of our members here.  Thanks!

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rxwxunc

rxwxunc

Posted
Posted

That's what I am expecting... still doesn't quite do it at 12z but is more amplified in the first 24-30 hours. One problem the GFS might have in these cases that are amplified by diabatic heating (and hence mid-level PV production) is that the model applies significant diffusion to dampen out smaller wavenumbers to prevent computational modes from growing exponentially and making the model crash. The negative impact of this increase in diffusion is that it sometimes dampens out important wave signals that could have implications beyond the short range in a forecast. The ECMWF to my knowledge doesn't use the same time differencing scheme so it doesn't need to apply as much diffusion to dampen the computational mode of smaller wavenumbers.

 

Non-techinical version... GFS is more likely to dampen out important features when there is a lot of convection being produced in a model solution (this is not the same as convective feedback since that is more related to a poor cummulus scheme overproducing precipitation in particular regiemes). 

Thanks for this very informative post. I am, like most members, trying to always learn about what makes these models tick.

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