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Major Severe Weather Outbreak November 17


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Between blasts of cold air, it looks like there will be a strong system with the potential to produce a severe weather outbreak at least into the Ohio Valley and quite possibly farther north. Too early for a lot of details but various solutions generally agree on a substantial surface low moving from the Plains to the Lakes late weekend/early next week with good moisture return for this time of year. Situation bears watching.

Discuss.

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Both the GFS and Euro show an initial system lifting out on Saturday that will help draw the warmth and moisture Northward with the second system for Sunday into Monday bringing the cold front through. I do agree this bears watching as there could be a decent potential of severe weather with the cold front, too early to get specific in the details though.

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Both the GFS and Euro show an initial system lifting out on Saturday that will help draw the warmth and moisture Northward with the second system for Sunday into Monday bringing the cold front through. I do agree this bears watching as there could be a decent potential of severe weather with the cold front, too early to get specific in the details though.

Some pretty notorious events have been preceded by a lead system...a sacrifical lamb. Not saying this is gonna be the outbreak of the century or anything like that but it's an important factor. Don't want that first one to get too strong though.

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Some pretty notorious events have been preceded by a lead system...a sacrifical lamb. Not saying this is gonna be the outbreak of the century or anything like that but it's an important factor. Don't want that first one to get too strong though.

 

Yes, a system to prime the pump for the region.

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Couldn't help myself and took a peek at some forecast soundings for the Ohio Valley off the 00z GFS. Needless to say, pretty impressive, especially if adjusted for what surface conditions may be like.

The wind profiles are exceptional on the GFS, obviously the 60-65 temps are being way underdone, it will be interesting to see once this gets into the range of the NAM what temperature profiles we will be seeing. The part that interests me the most however, is that the Euro, GGEM and especially the Ukie are much stronger with the low pressure system for the region, that would have huge implications with respect to the strength of the wind field and the moisture transport and warm air advection into the region.

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The wind profiles are exceptional on the GFS, obviously the 60-65 temps are being way underdone, it will be interesting to see once this gets into the range of the NAM what temperature profiles we will be seeing. The part that interests me the most however, is that the Euro, GGEM and especially the Ukie are much stronger with the low pressure system for the region, that would have huge implications with respect to the strength of the wind field and the moisture transport and warm air advection into the region.

 

06z GFS pushes 70s up to Lincoln, IL

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Area has been outlined for day 5

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0351 AM CST WED NOV 13 2013

VALID 161200Z - 211200Z

..DISCUSSION

ALTHOUGH CONSIDERABLE SPREAD PERSISTS WITHIN THE MEDIUM RANGE MODEL ENSEMBLE DATA...AND UNCERTAINTIES LINGER...THERE DOES APPEAR REASONABLE AGREEMENT BETWEEN AT LEAST THE GFS AND ECMWF ENSEMBLE MEANS CONCERNING LARGE-SCALE PATTERN DEVELOPMENTS LATE THIS WEEKEND INTO EARLY NEXT WEEK. THIS EXTENDS...AT LEAST TO SOME EXTENT...TO THEIR RESPECTIVE 13/00Z DETERMINISTIC RUNS...AND IT APPEARS INCREASINGLY LIKELY THAT SIGNIFICANT SURFACE CYCLOGENESIS WILL TAKE PLACE ALONG A SOUTH SURGING COLD FRONT TO THE LEE OF THE ROCKIES...FROM THE CENTRAL PLAINS INTO THE GREAT LAKES REGION. BEFORE THE COLD INTRUSION CUTS OFF MOISTURE RETURN FROM THE GULF OF MEXICO...A WINDOW OF OPPORTUNITY DOES APPEAR TO EXIST FOR THE DEVELOPMENT OF A CORRIDOR OF SUBSTANTIVE BOUNDARY LAYER DESTABILIZATION...IN THE PRESENCE OF STRONG DEEP LAYER SHEAR AND MID/UPPER FORCING FOR ASCENT...SUPPORTIVE OF THE RISK FOR SEVERE STORMS. THIS CURRENTLY SEEMS MOST LIKELY LATE SUNDAY AFTERNOON THROUGH SUNDAY NIGHT...FROM THE VICINITY OF THE ARKLATEX NORTHEASTWARD INTO THE MIDDLE MISSISSIPPI/LOWER OHIO VALLEY REGION...INCLUDING THE POTENTIAL FOR DAMAGING WIND GUSTS AND TORNADOES.

..KERR.. 11/13/2013

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12z Euro really goes to town with this. 980 mb low near the Lake Superior/Canada border at 120 hours.

IMO, the ceiling with this one is higher than what we saw on Halloween as this one at least looks like it could have somewhat greater instability.

That location and the strength is really the kicker here. We really had almost no instability here on Halloween and Ohio had quite a few severe reports, this seems very promising especially with a track into Lake Superior which almost always leads to good fortunes for the Lower GL

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12z Euro really goes to town with this. 980 mb low near the Lake Superior/Canada border at 120 hours.

IMO, the ceiling with this one is higher than what we saw on Halloween as this one at least looks like it could have somewhat greater instability.

I'd agree especially considering that the Halloween event had roughly 500-750 J/kg max and there were 46 tornadoes with that event. The Euro is pumping out 800-1200 J/kg along the front on Sunday already, and that is probably a bit underdone.

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One thing that really gets my attention is if the 12z Euro verbatim slows even by just 6 hrs, then you have something like the following occurring around peak heating for MO/IL and perhaps the D5 area (which with given the forecast temps and dewpoints probably means around 1000-2000 J/kg of CAPE over at least some of the area). Analysis of COD/wundermaps also shows southerly/backed sfc winds and a very impressive wind profile overall, with winds veering/increasing strongly with height.

 

rdpo.gif

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looking like a solid event in the making

Gil's take

Sunday is an eye-opener. Models portray nearly 60 degree dewpoints coming 
into the area by Sunday afternoon, as a strong cold front approaches our 
area. Moisture levels 3 standard deviations above average this time of 
year should always raise eyebrows, but what it will do will bring us lots 
of clouds. I am concerned that if we---or areas southwest of us---get into 
some sunshine, somehow, on Sunday...there would be enough instability and 
more than enough shear for severe thunderstorms. The Storm prediction 
Center has that risk over southern Illinois: 

http://www.spc.noaa.gov/products/exper/day4-8/

That could spread farther north if the European model has its way.
But, it's way too early to tell, and quite frankly, forecasting a
late-November severe weather event for our area is about as easy
as carving a Thanksgiving turkey blindfolded...while standing on a 
high-wire rope during a windy day. So for now, I just went for
thunderstorms on Sunday...and will keep watching the trends.
 

http://weather.admin.niu.edu/forecast.txt

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One thing that really gets my attention is if the 12z Euro verbatim slows even by just 6 hrs, then you have something like the following occurring around peak heating for MO/IL and perhaps the D5 area (which with given the forecast temps and dewpoints probably means around 1000-2000 J/kg of CAPE over at least some of the area). Analysis of COD/wundermaps also shows southerly/backed sfc winds and a very impressive wind profile overall, with winds veering/increasing strongly with height.

rdpo.gif

We're in big trouble if we're talking about CAPE like that.

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We're in big trouble if we're talking about CAPE like that.

1000 to 1500 J/kg certainly looks possible, especially if you were to modify soundings to the forecast highs by NWS, models are undercutting them by as much as 4 to 7 degrees.

Also, all there really needs to be is sufficient 0-3 km CAPE. Gino remarked today at work the similarities to setups in previous cold season tor episodes in the LOT CWA, but then that this one has a much stronger synoptic system. So if things come into line track/timing/mesoscale, ceiling is at least as high as 1/7/08 and 11/22/10.

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The system as a whole is less amplified and much more progressive than the 12z/18z runs. The second vort max is less intense and doesn't end up becoming independent of the lead wave. Since the best dynamics are leaving the instability axis behind, this run would likely imply a significantly lessened threat.

 

That said, the GFS has been having run-to-run continuity problems to a significantly greater degree than the Euro with this so we'll see if it holds water when the counterparts come out later.

 

HPC's early model diagnostic discussion tosses this verbatim:

...LONGWAVE TROUGH AMPLIFYING OVER THE WESTERN U.S. AND PLAINS  
SATURDAY AND SUNDAY...  
 
PREFERENCE: 12Z ECMWF/12Z ECENS MEAN BLEND  
CONFIDENCE: AVERAGE  
 
THE MODELS SHOW THE DEVELOPMENT OF A ROBUST LONGWAVE TROUGH OVER  
THE WESTERN U.S. THIS WEEKEND WHICH WILL BE GRADUALLY IMPACTING  
THE PLAINS. THE HEIGHT FALLS BY IN LARGE WILL BE DRIVEN BY STRONG  
REINFORCING SHORTWAVE/JET ENERGY DIGGING ACROSS THE NORTHWEST BY  
SAT. THE 12Z GEM GLOBAL AND 12Z UKMET ARE SOMEWHAT WEAKER/FASTER  
WITH THE ENERGY...COMPARED TO THE DEEPER 00Z NAM. THE 00Z GFS AND  
12Z ECMWF SPLIT THE DIFF WITH THE LONGWAVE TROUGH DETAILS...BUT  
THE 00Z GFS APPEARS TOO ROBUST/PROGRESSIVE WITH A LEAD SHORTWAVE  
IT HAS EJECTING OUT ACROSS THE PLAINS BY SAT NIGHT.  
CONSEQUENTLY...THE GFS APPEARS TOO STRONG WITH ITS SURFACE LOW  
DRIVING UP TOWARD THE UPPER MIDWEST SAT NIGHT/SUN.
THE 18Z GEFS  
MEAN AND 12Z ECENS MEAN SUPPORT THE 12Z ECMWF WITH LOW PRESSURE  
FOCUSED MORE BACK OVER THE PLAINS. WILL FAVOR A BLEND OF THE 12Z  
ECMWF AND 12Z ECENS MEAN. 

 

18z GFS valid 96 hrs:

90c.gif

 

00z GFS valid 90 hrs:

a0tv.gif

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