Christmas Storm VI

[FoothillsNC]

imo, the euro messed up a little bit right out of the gate with the southern TEX wave. It may have readjusted later on but that kind of worries me. I'd not trust it that much at this stage for that strong Tex wave. Go with RUC.

[Rankin5150]

A lot of cliff diving in the Northeast right now- this run screws everyone up there except Cape Cod

There is always a "DEVIL in the details". LMAO

[BullCityWx]

Do both models have good snow for the I-20 region from Bham to Atlanta ?

This stuff aint acceptable guys...I'm trying to catch up to all the offenders with posts like these.

[Tacoma]

thinking all snow from landrum north, rain snow mix to snow south of landrum and east toward charlotte during saturday.

[Wow]

imo, the euro messed up a little bit right out of the gate with the southern TEX wave. It may have readjusted later on but that kind of worries me. I'd not trust it that much at this stage for that strong Tex wave. Go with RUC.

euro is not a good short range model. verifies best among the group in the mid range 72-120 hrs

[tnweathernut]

looking like east tenn and wnc could get most snow when you include the wrap around after the initial event

would a met or someone who has access to qpf either confirm or deny this wrt east tn (speaking specifically to TYS and TRI)? It's hard for me to believe with all I have seen in the last three days and I can't confirm b/c I don't have access to all my data being at my mother and father in laws. Thanks to anyone that can help.

[FoothillsNC]

Can anybody confirm the HPC message and whats its exact implication is on the GFS init. problems? Anyway, I guess we're nowhere guarantteed anything, even if perfect data was ingested, this is still a close call and will come down to watching trends and the satellite and radar, RUC, etc. If it snows it snows, if not, I guess we'll soon find out.

[Wild Weather Monger]

Dr. Woo says

[NCSNOW]

euro is not a good short range model. verifies best among the group in the mid range 72-120 hrs

You can easily tell its gonna initialize wrong just by looking at current mosiac. No way the southern low is gonna be in LA/gom in 6 hours. Watch the 1 hour loop and multiply that distance times 6. Good to have Robert catch that one right off the bat.

[Poimen]

Can anybody confirm the HPC message and whats its exact implication is on the GFS init. problems? Anyway, I guess we're nowhere guarantteed anything, even if perfect data was ingested, this is still a close call and will come down to watching trends and the satellite and radar, RUC, etc. If it snows it snows, if not, I guess we'll soon find out.

This?:

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1235 PM EST FRI DEC 24 2010

VALID DEC 24/1200 UTC THRU DEC 28/0000 UTC

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR

INGEST...

12Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN AND

PREFERENCES

...SPLIT SHORTWAVE TROUGHS EXTENDING OVER THE PLAINS/MIDWEST...

...LOW PRESSURE FORMING ALONG THE EAST COAST THROUGH MONDAY...

PREFERENCE: EQUAL BLEND OF THE 06Z GFS/00Z ECMWF OR THE ENSEMBLE

MEANS

INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC

QUANTITIES...INCLUDING HEIGHT/VORTICITY FIELDS/RH...ARE EVIDENT IN

BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE

TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH

SASKATCHEWAN/MANITOBA...WITH THESE AREAS ALSO NOT PARTICULARLY

RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF.THUS...THE SPECIFIC

PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION...WITH

THE RECOMMENDATION TO FOLLOW CONTINUITY...WITH THE FINAL OUTCOME

MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF...WITH ALL

ENSEMBLE GUIDANCE INCLUDING THE SREF MEAN/GEFS MEAN/ECMWF ENSEMBLE

MEAN ALSO CONSIDERED USEFUL TO ADDRESS THE CONTINUED UNCERTAINTY.

THIS APPROACH DISREGARDS THE SUBSTANTIALLY DEEPER AND WESTWARD

SHIFT OF THE 12Z GFS REGARDING THE POWERFUL LOW TRACKING UP THE

EASTERN SEABOARD...AND TO A LESSER EXTENT THE 12Z NAM WHICH LIES

NEAR THE FAST EDGE OF THE GUIDANCE WITH THE DEVELOPING LOW.

THE NEW UKMET/CANADIAN ARE DIFFICULT TO EVALUATE FOR

INITIALIZATION SINCE WE RECEIVE A LIMITED AMOUNT OF DATA.

HOWEVER...THEIR SOLUTIONS LIE WITHIN THE EASTERN HALF OF THE

GUIDANCE ONCE THE INDIVIDUAL TROUGHS PHASE TO PRODUCE THE

DEEPENING LOW OFFSHORE...WHICH HAS CONSISTENTLY BEEN THE CASE.

THUS...INITIAL RECOMMENDATIONS ARE PRESERVED WITH CONTINUITY MOST

PREFERRED.

[HKY_WX]

http://www.nco.ncep....00_s_loop.shtml

checkout the polar shortwave. lol this is going to be an interesting 24 hours.

[BullCityWx]

Here's a QPF comparison for some selected cities:

Fayetteville(KFAY):

GFS: .89

NAM: .29

ECM: .48

Raleigh/Durham Intl(KRDU):

GFS: .81

NAM: .29

ECM: .28

Charlotte(KCLT):

GFS: .52

NAM: .25

ECM: .39

[georgiawx11]

12Z GFS shows thermal issues for Atlanta. .40" of precip but most is rain.

[Carvers Gap]

http://www.nco.ncep....00_s_loop.shtml

checkout the polar shortwave. lol this is going to be an interesting 24 hours.

I have been watching the same thing. It's going to be very close...

[hillbilly weather]

Any idea what the snow ratios would be?

[burrel2]

Hmm, the NAM forecasted around a 1/4 inch of liquid for southeastern Oklahoma today... Radar estimates are showing a strip of 2 to 3 inches of liquid has already fallen all the way into arkansas. Just sayin

[FoothillsNC]

This?:

thanks. Well looking at the long water vapor loops and radar loops in Texas, it looks to me like the center of the vort isn't going to come off Houston, but more like enter into western Louisiana, a litle further north than most models are showing. This is going to be the "devil" in the details that makes or breaks a forecast i think. Also, its very good looking, and may be entering a neutral tilt stage soon. I wonder how much the convection is changing things there.

In the last few hours of animation it looks like the center has been pulled north more and is on a more easterly heading. I think I read the latent heat added something to the ambient air which allowed a new path on systems like this, so its going to be fun to follow.

[NCSNOW]

36 hours in and here are your choices RAH NWS;

Take the 12 z GFS/ They will throw out due to HPC statement. I still dont have a clue what exactly initialized wrong and how off said factors are. (Big Hit)

Take the 12 z GFS ensemble (Big Hit)

Take the 12 z Euro (definetly suports a wwa 1-3 accum)

Any single one of those or a blend however you mix it up puts some part of their FA in WSW criteria.

Or you can run with the NAM solely or UKIE,CAN and no threat for reaching WSW criteria.

Tough Day to be a forecaster and this soap opera will have to play out another 12-18 hours minimum before anyone/models included will have a clue.

EDIT: Just throw in the towel and use a blend of the GFS ensemble/GFS OP/and JMA! Merry Christmas!

[oconeexman]

Robert, you may have to re-post your animated map from the other day!! Looking like a similar scenario now to me.

[kanc2001]

Hmm, the NAM forecasted around a 1/4 inch of liquid for southeastern Oklahoma today... Radar estimates are showing a strip of 2 to 3 inches of liquid has already fallen all the way into arkansas. Just sayin

doesnt NAM have a dry bias, or im I wrong?

[Reb]

is it just me or is the southern stream really connecting to the northern stream the last few frames here?

http://www.ssd.noaa.gov/goes/east/nwatl/loop-wv.html

[oconeexman]

Hmm, the NAM forecasted around a 1/4 inch of liquid for southeastern Oklahoma today... Radar estimates are showing a strip of 2 to 3 inches of liquid has already fallen all the way into arkansas. Just sayin

That's what i've been harping on for our area...it has consistently done bad with qpf up here as well, just give us the chance and think we'll be happy along and nw of the 85 corridor!

[Lookout]

This stuff aint acceptable guys...I'm trying to catch up to all the offenders with posts like these.

Something came up yesterday and didn't get back until a little while ago but it was nice to know you guys were around to handle things. I sure appreciate it.

I haven't dissected the models yet and I expected to see the models drier still when I got back but I'm a little surprised to see them wetter. The euro's 0.50 amounts in the upstate/northern midlands is surprising..as well as being in the 0.25 to 0.50 here.

The main concern I have is temps. The nam/gfs have temperatures a little on the warm side, however the wetbulb temps support snow all the way to the surface. However, gfs/nam don't saturate the boundary layer enough to reach those temps and based on the amount of precip they are showing, I don't think they are handling the evaporational cooling very well.

I hope anyway, it would suck big time to end up with very little after tracking this thing so closely for days.

[dsaur]

12Z GFS shows thermal issues for Atlanta. .40" of precip but most is rain.

Yeah, I was looking at that. 850's get ok, but I don't like that there is no help from the dp. Just need that northern stream sw to tuck and not over shoot. Get some good cold in here. T

[tnweathernut]

doesnt NAM have a dry bias, or im I wrong?

typically, the nam actually has a wet bias. A lot of short range forecasts for qpf I have seen, actually verify under the projected.

[eyes2theskies]

I would hate to be all of the local NWS right now. I think they will stand pretty firm with the afternoon disco's but if things keep trending the way they are we would be waking up to quite a few winter weather warnings. Good thing a lot of people will not be traveling tomorrow. This should be quite an interesting evening.

[FoothillsNC]

http://www.nco.ncep....00_s_loop.shtml

checkout the polar shortwave. lol this is going to be an interesting 24 hours.

Hmm, the NAM forecasted around a 1/4 inch of liquid for southeastern Oklahoma today... Radar estimates are showing a strip of 2 to 3 inches of liquid has already fallen all the way into arkansas. Just sayin

Good catch. The system is stronger and has more convection than forecast.

Robert, you may have to re-post your animated map from the other day!! Looking like a similar scenario now to me.

I was just using what I thought was that big Euro after 5 runs, and didn't even post it on here, some one else did. But yeah, nothing would suprise me on this event now.

[oconeexman]

Good catch. The system is stronger and has more convection than forecast.

I was just using what I thought was that big Euro after 5 runs, and didn't even post it on here, some one else did. But yeah, nothing would suprise me on this event now.

I've got it saved because it was dream scenario and an awesome animation. Gonna be a fun night...again! And are you going to update your blog tonight or morning?

[Lookout]

thanks. Well looking at the long water vapor loops and radar loops in Texas, it looks to me like the center of the vort isn't going to come off Houston, but more like enter into western Louisiana, a litle further north than most models are showing. This is going to be the "devil" in the details that makes or breaks a forecast i think. Also, its very good looking, and may be entering a neutral tilt stage soon. I wonder how much the convection is changing things there.

In the last few hours of animation it looks like the center has been pulled north more and is on a more easterly heading. I think I read the latent heat added something to the ambient air which allowed a new path on systems like this, so its going to be fun to follow.

What you are describing sounds like that huge snowstorm in jan 2000 the models missed handled. It's actually been in the back of my mind the last couple of days...was wondering if the convection associated with our southern system actually would cause something similar to that one. I figure this is a long shot but this is sort of unique system with respect to the setup so maybe the models haven't got a good handle on it. Probably wishful thinking though and I would still be happy with a dusting at this point.

Here is the relevant part with respect to the convection and it's effects from ncsu

Incipient Precipitation and Latent Heat

An area of precipitation developed along a frontal system over southern Alabama and southern Mississippi at around 06Z on January 24, 2000. The area of precipitation expanded and intensified as it moved into the cold airmass north of the front in Georgia by 12Z on January 24. Analysis of surface observations and radar imagery show that this area of precipitation was poorly forecast by the Eta model. Research into this storm indicates that this under forecasted area of precipitation that fell into a cold and somewhat dry airmass across the Deep South had a significant impact in how the models handled the developing storm system.

Based on quasi-geostrophic (QG) theory, height rises (falls) occur above (below) a mid-level latent heating maximum, due to changes in the density of the air above and below. This response also creates a low-level maximum in cyclonic potential vorticity (PV), as low-level static stability is increased. The effects of the induced cyclonic PV max are manifest in wave amplification and enhanced rotation around the PV center. The precipitation across the Deep South induced a PV anomaly that enhanced the easterly flow downstream, creating stronger westward moisture advection over the Carolinas from off the Atlantic (Brennan and Lackmann 2005), thereby extending the heavy snowfall further inland. The inability of the models to accurately predict the precipitation across the Deep South was a major reason that the model forecasts of this storm were so inaccurate.

[Carvers Gap]

thanks. Well looking at the long water vapor loops and radar loops in Texas, it looks to me like the center of the vort isn't going to come off Houston, but more like enter into western Louisiana, a litle further north than most models are showing. This is going to be the "devil" in the details that makes or breaks a forecast i think. Also, its very good looking, and may be entering a neutral tilt stage soon. I wonder how much the convection is changing things there.

In the last few hours of animation it looks like the center has been pulled north more and is on a more easterly heading. I think I read the latent heat added something to the ambient air which allowed a new path on systems like this, so its going to be fun to follow.

Foothills. What are impacts on sensible weather if this low tracks through Louisiana? Does that imply a coastal low or OTS? If the northern stream digs more and the vort is more northerly, does that mean a phase is more or less likely?