18z 12/24 model disco

[LVblizzard]

10 out of 12 members are a big MA hit. 2 appear to still be light snow/fringes, but good hit further north.

http://www.meteo.psu.edu/~gadomski/ENSPRSNE_18z/f54.html

In the 12z GEFS one member missed everybody except eastern MA. That seems to have corrected itself.

[Kaner587]

10 out of 12 members are a big MA hit. 2 appear to still be light snow/fringes, but good hit further north.

http://www.meteo.psu...NE_18z/f54.html

thats a gigantic signal if I've ever seen one...that or the GFS has got a hold of some of that green

[yoda]

For those of you wanting the Earl Barker snowfall maps... here is out to 45 hrs

[Eskimo Joe]

For those of you wanting the Earl Barker snowfall maps... here is out to 45 hrs

Can you please provide the link? Thanks!

[yoda]

Can you please provide the link? Thanks!

http://wxcaster.com/regional_snowfall.htm

[Dcwx]

For those of you wanting the Earl Barker snowfall maps... here is out to 45 hrs

Great hit for NC, awesome Christmas snow for the Atlanta area.

[Blizzard-on-GFS]

Can you please provide the link? Thanks!

http://wintercast.tripod.com/id14.html

[yoda]

[Clinch Leatherwood]

By about 8pm we should have a much better idea as 0z UA is in. Right now I see a few things that are raising a red flag on the 6h GFS product:

1. The s/w in texas seems to have unwound a bit in terms of structure. It's elongated, the GFS had a tight spiral. That's important because if the ob is correct - and the RUC, the actual s/w center will be displaced a little bit NE/faster. There is very clearly two lobes of vorticity.

2. The GFS may be a little fast with the feature coming into the western dakotas.

Both of these things have become apparent in the last 5 or so frames of the w/v. Just my observations but it does call into question the GFS. I wish we had a method for comparing it to other misses.

Those are both pretty significant IMO.

EDIT: As a third the vortmax spinning down towards MN looks more impressive than modeled but not by a ton, just more defined.

[Kaner587]

By about 8pm we should have a much better idea as 0z UA is in. Right now I see a few things that are raising a red flag on the 6h GFS product:

1. The s/w in texas seems to have unwound a bit in terms of structure. It's elongated, the GFS had a tight spiral. That's important because if the ob is correct - and the RUC, the actual s/w center will be displaced a little bit NE/faster.

2. The GFS may be a little fast with the feature coming into the western dakotas.

Both of these things have become apparent in the last 5 or so frames of the w/v. Just my observations but it does call into question the GFS. I wish we had a method for comparing it to other misses.

Those are both pretty significant IMO.

I welcome your analysis of the proposed issues on the information that went into both the 12z and 18z GFS that caused HPC to toss it, but they made no mention of the southern stream energy so instead of analyzing the GFS look at all models with this feature. Otherwise agreed about looking at WV imagery and whatever info is available to see how the northern stream s/w is digging/moving WSW.

[ptb127]

My god... .50-.75" would-be a good hit. Is there real obs imputed in the 18z GFS?

[snowdude]

Sterling update in case no one read....

*JUST A QUICK UPDATE. 18Z GFS TRENDING CLOSER TO THE CST W/ THE

SUNDAY EVENT...W/ 15Z SREF DOING SAME. WE`RE NOT GOING WILD...BUT

WE`LL ADD 10% ON TO THE POPS FOR THE ERN PART OF THE AREA FOR SUN

AFTN. THIS WL INCRS LWR SRN MD TO LKLY. 6PM UPDATE WL REFLECT

THIS CHG. NOT SURE THAT WE`LL HV MUCH NEW GDNC TO LOOK AT FOR THE

9PM UPDATE...BUT THE 00Z NAM WL START TO COME IN ARND THAT TIME

TO GIVE US A BETTER IDEA.

[yoda]

[Eskimo Joe]

By about 8pm we should have a much better idea as 0z UA is in. Right now I see a few things that are raising a red flag on the 6h GFS product:

1. The s/w in texas seems to have unwound a bit in terms of structure. It's elongated, the GFS had a tight spiral. That's important because if the ob is correct - and the RUC, the actual s/w center will be displaced a little bit NE/faster. There is very clearly two lobes of vorticity.

2. The GFS may be a little fast with the feature coming into the western dakotas.

Both of these things have become apparent in the last 5 or so frames of the w/v. Just my observations but it does call into question the GFS. I wish we had a method for comparing it to other misses.

Those are both pretty significant IMO.

EDIT: As a third the vortmax spinning down towards MN looks more impressive than modeled but not by a ton, just more defined.

Good points on the strength and placement of the vortmaxes. I am not worried at all about the Texas feature "unwinding". If you take a look at the top left portion of the image below, you will notice the energy level associated with the Texas shortwave is still very robust and still appears to be digging!

[Doppler5]

My god... .50-.75" would-be a good hit. Is there real obs imputed in the 18z GFS?

New aircraft data is given to the 18z but there are no new upper air soundings lauched for the 18z runs.

[weatherweather]

By about 8pm we should have a much better idea as 0z UA is in. Right now I see a few things that are raising a red flag on the 6h GFS product:

1. The s/w in texas seems to have unwound a bit in terms of structure. It's elongated, the GFS had a tight spiral. That's important because if the ob is correct - and the RUC, the actual s/w center will be displaced a little bit NE/faster. There is very clearly two lobes of vorticity.

2. The GFS may be a little fast with the feature coming into the western dakotas.

Both of these things have become apparent in the last 5 or so frames of the w/v. Just my observations but it does call into question the GFS. I wish we had a method for comparing it to other misses.

Those are both pretty significant IMO.

EDIT: As a third the vortmax spinning down towards MN looks more impressive than modeled but not by a ton, just more defined.

Good points, but current conditions are def closer to18z models than 6z.

[chris87]

Yes, lots of observations are taking every hour of every day. Surface obs, wind profilers...but most of the observations come from the direct assimilation of satellite radiances (from both geostationary and polar orbiting). Outside of RAOBs, assimilation of microwave radiances (instruments like AMSU) are the most important observations when it comes to assimilation impact.

to put it into context...the operational centers assimilate millions of observations every day

My god... .50-.75" would-be a good hit. Is there real obs imputed in the 18z GFS?

[JBG]

My god... .50-.75" would-be a good hit. Is there real obs imputed in the 18z GFS?

Is this wishcasting or for real?

Even this curmudgeon is starting to get excited.

[aldie 22]

My god... .50-.75" would-be a good hit. Is there real obs imputed in the 18z GFS?

The ratios would be insane

[ptb127]

The ratios would be insane

Yea.. Could be 18:1

[blizzard00]

honestly i've compared the GFS runs over the last 24 hours and there haven't been any noticable changes at the 500mb level

[Clinch Leatherwood]

Good points on the strength and placement of the vortmaxes. I am not worried at all about the Texas feature "unwinding". If you take a look at the top left portion of the image below, you will notice the energy level associated with the Texas shortwave is still very robust and still appears to be digging!

Eskimo Joe, it would be an enormous help if you wouldn't mind posting the data on the left as is current at 0z for that feature and those from the dakotas to Iowa.

It would really allow us to get to the bottom of this pretty quickly.

The strength is great, the elongated nature of it would tend to make me think a compromise is occuring...ie there is bad data which upstream caused changes which had the american models holding a bowling ball instead of a a more elongated albeit stronger feature.

More importantly it appears to me the GFS/NAM were bringing the energy south a little fast in the Dakotas.

[Eskimo Joe]

Eskimo Joe, it would be an enormous help if you wouldn't mind posting the data on the left as is current at 0z for that feature and those from the dakotas to Iowa.

It would really allow us to get to the bottom of this pretty quickly.

The strength is great, the elongated nature of it would tend to make me think a compromise is occuring...ie there is bad data which upstream caused changes which had the american models holding a bowling ball instead of a a more elongated albeit stronger feature.

More importantly it appears to me the GFS/NAM were bringing the energy south a little fast in the Dakotas.

Ask and you shall receive. Here is the 500mb analysis as of 6:40pm, 20min before 00z. Hope this helps! FWIW, I think the 18z GFS is handling the two features nicely.

[Clinch Leatherwood]

New aircraft data is given to the 18z but there are no new upper air soundings lauched for the 18z runs.

Huge point for two reasons:

1. Christmas eve flight volume normally.

2. Thousands of flights were again cancelled into and out of europe including flights into the US. We are getting a lower sampling of data than we would normally get. Bad timing really.

3. Thousands of flights are being altered today. Delta has already cancelled about 500 out of Atlanta on XMas for weather reasons which means those planes were held elsewhere and weren't in the air potentially today.

In a nutshell IMO a bad combination of events. Models choked on some bad data at 12z, and we have a bundle of flights cancelled across europe into major US hubs, and domestic flights being scrubbed for weather. Ouch.

[Clinch Leatherwood]

Ask and you shall receive. Here is the 500mb analysis as of 6:40pm, 20min before 00z. Hope this helps! FWIW, I think the 18z GFS is handling the two features nicely.

Thanks and I'll look for the 0z...running downstairs to keep the peace before my wife stabs me in the eye and this is all a moot point

[Eskimo Joe]

Huge point for two reasons:

1. Christmas eve flight volume normally.

2. Thousands of flights were again cancelled into and out of europe including flights into the US. We are getting a lower sampling of data than we would normally get. Bad timing really.

3. Thousands of flights are being altered today. Delta has already cancelled about 500 out of Atlanta on XMas for weather reasons which means those planes were held elsewhere and weren't in the air potentially today.

In a nutshell IMO a bad combination of events. Models choked on some bad data at 12z, and we have a bundle of flights cancelled across europe into major US hubs, and domestic flights being scrubbed for weather. Ouch.

I wouldn't lose sleep over that. As previously stated, satellite data is also ingested along with other data mediums. It's not just aircraft alone.

[LakeEffectKing]

From ALB:

MAJOR EAST COAST STORM APPEARS TO BE EAST OF OUR FORECAST

AREA...OR DOES IT?...

AS OF 5PM... NCEP 18Z MODEL DATA HAS ARRIVED WITH A TREND A FURTHER

TO THE WEST WITH THE UPCOMING SUN-MON EVENT. AS NOTED

BELOW...INITIAL ERROR CONDITIONS REMAIN WITH DOWNSTREAM IMPACTS

QUITE DRAMATIC. PER THE GFS...CONVECTIVE FEEDBACK DOES SEEM

PLAUSIBLE ACROSS THE SOUTHEAST CONUS AND TIMING OF THOSE UPSTREAM

WAVES REMAINS IN QUESTION. LATEST ENSEMBLE INFORMATION FROM THE

GFS/SREF/ECMWF ALSO SUGGEST A POSSIBLE WESTWARD SHIFT. SO OVERALL

CONFIDENCE REMAINS RATHER LOW AT THIS TIME AS WE WILL CONTINUE TO

CLOSELY MONITOR UPSTREAM TRENDS. LETS HOPE THE 00Z RAOB NETWORK

TONIGHT CAPTURES THE KEY FEATURES...

WE WILL LEAVE THE HWO ALONE AND THE CURRENT FORECAST/GRIDS.

PREV DISCUSSION...

THIS HOLIDAY WEEKEND...PLENTY OF ATTENTION ON THE DEVELOPING EAST

COAST CYCLOGENESIS. NCEP MODEL SUITE...ALONG WITH INTERNATIONAL

GLOBAL MODELS...MAINLY FAVOR THE FURTHER OFFSHORE SOLUTION ON THIS

EVOLVING STORM. HERE ARE A FEW KEY ELEMENTS THAT THE MODELS ARE

HAVING CHALLENGES WITH THE INITIALIZATION TODAY...

1. H2O VAPOR IMAGERY REVEALS A VERY TIGHT/STRONG SHORT WAVE OVER

CENTRAL TEXAS.

2. A FAST MOVING SHORT WAVE OVER SOUTHEAST NEBRASKA APPROACHING

MISSOURI.

3. ADDITIONAL COMPLEX WAVES OVER SASKATCHEWAN/MANITOBA

THAT CONTINUE TO DIVE SOUTHWARD...ALBEIT SLOWER MOVEMENT THAN THE

DOWNSTREAM WAVE OVER NE/MO.

4. UPPER FLOW AND TROUGH ORIENTATION REMAINS POSITIVELY TILTED AT

THIS TIME.

THROUGH EXTENSIVE COLLABORATION WITH NEIGHBORING OFFICES AND

HPC...THE 12Z GFS WAS DISCOUNTED. THE MODEL DID NOT INITIALIZE

WELL WITH ERRORS IN THE HEIGHT FIELD OVER NE AND NORTH CENTRAL

CANADA. ERRORS APPEAR TO BE LESS WITH THE 12Z

NAM/GGEM/ECMWF/UKMET. THE GFS AMPLIFIES THESE ERRORS...ALONG WITH

WHAT SEEMS TO BE INCREASED CONVECTIVE FEEDBACK...FOR RAPID

DEEPENING OF THE EAST COAST CYCLOGENESIS SUN-MON AND VERY CLOSE

TO THE SHORELINE /IN OTHER WORDS...A MAJOR STORM FOR THE FORECAST

AREA/. THIS TOO APPEARS TO HAVE IMPACTED ITS ENSEMBLE MEMBERS

WITH ASSOCIATED PERTURBATIONS OFF THESE ERRORS.

SO WE HAVE FOLLOWED THE CONSENSUS WHICH IS IN CLOSE AGREEMENT TO

OUR PREVIOUS FORECAST. WE WILL KEEP THE CHANCE FOR LIGHT SNOW IN

THE GRIDS/FORECAST BEGINNING OVERNIGHT SATURDAY THROUGH MONDAY

MORNING. THIS WILL BE DUE TO THE EVOLVING UPPER LOW /CYCLONIC

FLOW/ AND DEFORMATION DYNAMICS AS THIS STORM TRACKS EAST OF CAPE

COD SUNDAY NIGHT. QPF AMOUNTS REMAIN LIGHT AT THIS TIME...WITH

SOME UPSLOPE ENHANCEMENTS WITH THE INCREASED NORTHERLY FLOW.

WINDS WILL BE ON THE INCREASE DUE TO THE TIGHTENING PRESSURE

GRADIENT SUNDAY NIGHT THROUGH MONDAY COINCIDING WITH COLD

ADVECTION AS 850MB TEMPS DROP TO AROUND -10C. WIND CHILL VALUES

ARE EXPECTED TO REMAIN BETWEEN 0F AND 10F.

[snowman21]

Ask and you shall receive. Here is the 500mb analysis as of 6:40pm, 20min before 00z. Hope this helps! FWIW, I think the 18z GFS is handling the two features nicely.

How is there a new 500-mb analysis before the 00z RAOBs are in? I see you're using simuawips and always wondered how their U/A analysis change almost hourly and how legit it was.

[CT Rain]

Huge point for two reasons:

1. Christmas eve flight volume normally.

2. Thousands of flights were again cancelled into and out of europe including flights into the US. We are getting a lower sampling of data than we would normally get. Bad timing really.

3. Thousands of flights are being altered today. Delta has already cancelled about 500 out of Atlanta on XMas for weather reasons which means those planes were held elsewhere and weren't in the air potentially today.

In a nutshell IMO a bad combination of events. Models choked on some bad data at 12z, and we have a bundle of flights cancelled across europe into major US hubs, and domestic flights being scrubbed for weather. Ouch.

Also keep in mind the models assimilate a ton of remotely sensed data from satellites. The lack of aircraft data is not nearly as significant as it was a couple years ago.

[SBUWX23]

How is there a new 500-mb analysis before the 00z RAOBs are in? I see you're using simuawips and always wondered how their U/A analysis change almost hourly and how legit it was.

Not speaking for Eskimo Joe here but its probably using RUC data like the SPC Mesoanalysis.