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January 3-6th Winter Storm Part 2


Chicago Storm

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This may not be as good a system to use this as a proxy for, but typically the location of the potential vorticity (PV) anomaly hook is a decent telltale for a farther northwest track of a synoptic system. It worked very well with the November 17th tornado outbreak and also the 12/21-12/22 storm. Big difference here is the likelihood of less warm sector convection. Nonetheless, I plotted the 500-300 mb PVU surface (used that layer because the tropopause is going to be much lower in this setup than usual) at work this evening and for both the GFS (18z) and the Euro (12z) the location of the PV hook for each suggested a slightly farther northwest track is possible, with the "hook" pointing to southwest IL then into southwest IN in general.

 

In a talk that Victor Gensini of COD and NIU gave at our winter weather workshop (that I mentioned before 11/17), he specifically referenced GHD in that the GFS consistently placed the SLP well east of the PV anomaly, while interestingly enough, within 24 hours the NAM handled this better even though it's not a global model. Result was the farther NW track that brought the sleet apocalypse just southeast of the deformation axis snows and a bust for the blizzard warning for much of the STL area. The NAM clearly is an inconsistent model, but it *should* have a better handle with things like the fgen snows over northern IL behind the surface front because the frontogenetic circulation is more of a mesoscale feature. For the synoptic system, we'll have to see, there's valid reasons mentioned earlier how there's a limit on how far NW it can go, but I'm continuing to favor a track a bit northwest of the Euro and especially the GFS. 

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Model Disco including Euro.

 

 

 

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
142 AM EST SAT JAN 04 2014

VALID JAN 04/0000 UTC THRU JAN 07/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


NORTHERN STREAM SHORTWAVE TROUGH/SURFACE LOW(S) IMPACTING THE
N-CNTRL U.S. TODAY
COLD FRONT CROSSING THE CENTRAL U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE GUIDANCE IS IN GOOD AGREEMENT OUTSIDE OF THE 00Z NAM WHICH
SLOWED DOWN WITH THE MID-LEVEL SHORTWAVE EARLY TODAY OVER THE
N-CNTRL STATES. THE PREVIOUS 12Z NAM APPEARED OKAY AND IT IS NOT
CLEAR WHY THE RECENT NAM SHIFTED SLOWER. REMAINING MODEL GUIDANCE
FORMS A GOOD COMPROMISE.


BURGEONING TROUGH MID-CONTINENT
SURFACE LOW TRACKING FROM THE SRN PLAINS TO THE LOWER GREAT LAKES
FROM SAT THROUGH MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/CANADIAN/GFS COMPROMISE
CONFIDENCE: AVERAGE

THE ENSEMBLES HAVE COME INTO MUCH BETTER AGREEMENT WITH A SURFACE
LOW EXPECTED TO TRACK FROM THE SRN PLAINS INTO QUEBEC BY MON
MORNING...WITH THE EC...GEFS...AND CMC MEMBERS MOSTLY AGREEING ON
A POSITION NOW. THE 00Z UKMET ADJUSTED QUICKER FROM ITS 12Z
RUN...BUT IS STILL SLOWER THAN THE CONSENSUS...WHILE THE NAM IS
THE STRONGEST OF THE DETERMINISTIC MODELS. THE 00Z GFS/ECMWF/CMC
HAVE GOOD AGREEMENT AND REPRESENT THE BEST COMPROMISE OF THE
CURRENT AVAILABLE MODELS.
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This may not be as good a system to use this as a proxy for, but typically the location of the potential vorticity (PV) anomaly hook is a decent telltale for a farther northwest track of a synoptic system. It worked very well with the November 17th tornado outbreak and also the 12/21-12/22 storm. Big difference here is the likelihood of less warm sector convection. Nonetheless, I plotted the 500-300 mb PVU surface (used that layer because the tropopause is going to be much lower in this setup than usual) at work this evening and for both the GFS (18z) and the Euro (12z) the location of the PV hook for each suggested a slightly farther northwest track is possible, with the "hook" pointing to southwest IL then into southwest IN in general.

 

In a talk that Victor Gensini of COD and NIU gave at our winter weather workshop (that I mentioned before 11/17), he specifically referenced GHD in that the GFS consistently placed the SLP well east of the PV anomaly, while interestingly enough, within 24 hours the NAM handled this better even though it's not a global model. Result was the farther NW track that brought the sleet apocalypse just southeast of the deformation axis snows and a bust for the blizzard warning for much of the STL area. The NAM clearly is an inconsistent model, but it *should* have a better handle with things like the fgen snows over northern IL behind the surface front because the frontogenetic circulation is more of a mesoscale feature. For the synoptic system, we'll have to see, there's valid reasons mentioned earlier how there's a limit on how far NW it can go, but I'm continuing to favor a track a bit northwest of the Euro and especially the GFS. 

 

This is how all of the local mets in STL feel and why Chris Higgins has this.  But I am sure we can use our imagination bending the 8-12 band towards LAF just a bit.

 

If the stronger more NW solutions verify there could be a historic 12-18" band from STL to between Indy/Laf.

 

 

I would ignore East of the STL metro. 

 

Reasoning:

 

 

After pouring through the data... the changes I'm making are very limited.  The key features...especially the 850mb low and the 500mb vort max are all handled in a very similar fashion.  The consensus 850mb low track is still from southwest MO corner...east/northeast to near or just north of Fredericktown, MO....up over Perryville, MO...then northeast to near Mount Vernon.  The 500mb vort max tracks are a little more squirrely...especially on the GFS...but the general average takes the center of the vort max out of OK up into far south-centeral MO...then up over Poplar Bluff...then really stretches it out as it moves over to Paducah. 

Using those two tracks as a guide...per the GYB technique... still puts the axis of heavy snow further north from virtually every model QPF output...arguing for something along the lines of Nevada MO... through about Jeff City...up to near Alton, IL...then east/northeast from there.  As our good friend Fred Glass mentioned in his AFD... the snow may end up closer to the 850mb low track due to the artic air mass...which is certainly possible.  With that in mind... I have decided to ease the southern edge of my 8-12" range ever so slightly further south...while holding firm on the north end...consistent with the GYB technique.  It is extremely rare to get significant snow southeast of the track of the 850mb low...so I will use that as the limit  of my 5-8" band...with the 500mb vort track serving as my southern most accumulating snow boundary.

The northern edge of the accumulating snow will be rather sharp...which is not unusual.  Using the 700mb chart from the GEM and Euro offers a good idea of where that sharp cut off should be...just north of the strong troughing/convergence zone...or from about halfway between Quincy and Bowling Green...down to just west of Columbia.

 

 

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This may not be as good a system to use this as a proxy for, but typically the location of the potential vorticity (PV) anomaly hook is a decent telltale for a farther northwest track of a synoptic system. It worked very well with the November 17th tornado outbreak and also the 12/21-12/22 storm. Big difference here is the likelihood of less warm sector convection. Nonetheless, I plotted the 500-300 mb PVU surface (used that layer because the tropopause is going to be much lower in this setup than usual) at work this evening and for both the GFS (18z) and the Euro (12z) the location of the PV hook for each suggested a slightly farther northwest track is possible, with the "hook" pointing to southwest IL then into southwest IN in general.

 

In a talk that Victor Gensini of COD and NIU gave at our winter weather workshop (that I mentioned before 11/17), he specifically referenced GHD in that the GFS consistently placed the SLP well east of the PV anomaly, while interestingly enough, within 24 hours the NAM handled this better even though it's not a global model. Result was the farther NW track that brought the sleet apocalypse just southeast of the deformation axis snows and a bust for the blizzard warning for much of the STL area. The NAM clearly is an inconsistent model, but it *should* have a better handle with things like the fgen snows over northern IL behind the surface front because the frontogenetic circulation is more of a mesoscale feature. For the synoptic system, we'll have to see, there's valid reasons mentioned earlier how there's a limit on how far NW it can go, but I'm continuing to favor a track a bit northwest of the Euro and especially the GFS. 

 

 

Great post and great thoughts, I have to agree with you here especially about the fgen. If I had to pick a track with the synoptic system I would probably pick something close to the RGEM from 00z maybe a touch east of that. The NAM is a bit unrealistically left on this one, and like we have seen all winter, will correct east some throughout the day today. Like you mention though, I also agree the GFS/Euro combo is a bit too far east on this one and will probably correct left a bit throughout the day.

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