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Major Severe Weather Outbreak November 17


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I'm gonna make this quick since it's late and I'm pretty tired.  I just want to summarize why I think this system has a good deal of potential, even though question marks still exists with regard to exact timing and evolution of the trough.

 

There are two things that really stand out to me in terms of the ceiling for this event.

 

1) The position of the subtropical ridge over the Atlantic.  This is my #1 synoptic key for almost cold season severe wx event, especially the farther N we're talking.  When I reference this, I mean the fact that the sfc high is strong and is centered >40N.  This has two critical effects.  The first is that cP air is blocked from ever having the chance to recycle around the ridge and contaminate moisture return.  The second is that it is an ideal setup to really tap deep into the Gulf and the Caribbean and effectively advect moisture northward.  We've seen this several times in recent cold season tornado events, with 1/7/08 and 11/22/10 really particularly coming to mind.  This point works to effectively eliminate the #1 concern with most cold-season events, which is the quality of moisture return.  It's going to be there in earnest with this one, folks.  In earnest.

 

2) There's nothing to contaminate the warm sector lapse rates.  Unlike Halloween, we don't have an EPac hurricane off which to advect a ton of mid-level moisture, kill lapse rates over a large area, and promote copious stratiform rainfall.  Plus, given the orientation of this trough and that fact that it doesn't really dig a whole ton in the SW, the potential for lapse rate contamination is reduced.

 

I don't want to speculate too much on where the highest threat is right now until the low track and timing are more securely nailed down.  But anywhere from Chicago and South Bend down to St. Louis, Indianapolis, Louisville, Memphis, Little Rock, Nashville, Huntsville, and maybe as far south and Birmingham, Tuscaloosa, and even Jackson really need to pay attention to this.

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Generally when you throw the two main things Tony mentions with a significantly deepening (potentially even bombing) surface cyclone and strong wind fields throughout the column, some sort of trouble is not far around the corner. The rest of the model suite did not go for the 00z GFS' idea.

 

Add on the expected sfc conditions with high temps anywhere from 65˚F and up to even approaching 80˚F further south, and that becomes a volatile cocktail.

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Damn, big time D4 area...

 

ujx2.gif

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CST THU NOV 14 2013

VALID 171200Z - 221200Z

...DISCUSSION...
SOME UNCERTAINTY LINGERS...BUT TRENDS IN THE MEDIUM RANGE FORECAST
GUIDANCE ARE INCREASINGLY SUGGESTIVE OF THE DEVELOPMENT OF AN
ENVIRONMENT SUPPORTIVE OF AN OUTBREAK OF SEVERE THUNDERSTORMS ACROSS
PARTS OF THE MIDDLE MISSISSIPPI VALLEY EASTWARD THROUGH MUCH OF THE
OHIO VALLEY ON SUNDAY.
MOST GUIDANCE NOW APPEARS GENERALLY FASTER
WITH THE CONTINUED EASTWARD PROGRESSION OF A STRONG SHORT WAVE
TROUGH...FROM THE CENTRAL PLAINS EARLY SUNDAY TO THE LOWER GREAT
LAKES/UPPER OHIO VALLEY/CENTRAL APPALACHIANS REGION BY LATE SUNDAY
NIGHT. MOST MODELS ARE NOW SUGGESTIVE THAT THIS WILL BE ACCOMPANIED
BY STRONG SURFACE CYCLOGENESIS...WITH MOST RAPID SURFACE PRESSURE
FALLS ACROSS PARTS OF THE GREAT LAKES REGION AND OHIO VALLEY LATE
SUNDAY AFTERNOON INTO SUNDAY NIGHT.

A 90+ KT 500 MB JET STREAK NOSING THROUGH THE OHIO VALLEY...COUPLED
WITH STRENGTHENING SOUTHERLY WARM SECTOR 850 MB FLOW...PERHAPS IN
EXCESS OF 70 KTS ACROSS PARTS OF THE OHIO VALLEY INTO THE LOWER
GREAT LAKES...WILL CONTRIBUTE TO VERY STRONG DEEP LAYER WIND FIELDS
AND SHEAR. IT ALSO APPEARS INCREASINGLY PROBABLE THAT THIS WILL
COINCIDE WITH AN INFLUX OF SEASONABLY HIGH MOISTURE CONTENT AT LEAST
AS FAR NORTH AND EAST AS THE LOWER OHIO VALLEY...CONTRIBUTING TO
SUFFICIENT CAPE FOR VIGOROUS STORM DEVELOPMENT. SUPERCELLS WITH A
RISK FOR TORNADOES WILL BE POSSIBLE...PARTICULARLY IN EARLY STAGES
OF CONVECTIVE DEVELOPMENT...PERHAPS AS EARLY AS MID DAY ACROSS PARTS
OF THE MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEY VALLEY.

EVENTUALLY...THOUGH...ACTIVITY PROBABLY WILL EVOLVE INTO A SQUALL
LINE WITH DAMAGING STRAIGHT-LINE WINDS BECOMING THE MOST PROMINENT
SEVERE THREAT. IT MAY NOT BE OUT OF THE QUESTION THAT THIS COULD
PROGRESS INTO PARTS OF THE MID ATLANTIC SEABOARD AND NORTHEAST LATE
SUNDAY NIGHT INTO MONDAY...BUT THIS IS STILL TOO UNCERTAIN TO
DELINEATE A REGIONAL SEVERE RISK AREA EAST OF THAT CURRENTLY
DEPICTED. THEREAFTER...CONVECTIVE POTENTIAL THROUGH THE REMAINDER
OF THE PERIOD APPEARS LOW.

..KERR.. 11/14/2013
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I expected an expansion of the risk area Northward, I didn't expect it to go all the way to here though.

 

The 06z run of the GFS is much closer to the rest of the models, I would completely discount the 00z GFS at this point. Also this is getting into the range of the NAM now, and it is showing widespread 1000+ J/kg from Southern Wisconsin all the way down the front. You just don't see instability like that at this time of the year, and mind you that isn't even at peak heating, that is only at 18z. That would be a much more realistic thermodynamic profile with respect to this system when compared to the GFS. The ceiling for this event is already high considering the kinematics with the strong and strengthening low, adding in instability of 750-1250J/kg and things will probably go in a big way. This certainly looks to be the biggest potential this region has had all year, I also expect the GFS to correct closer to the rest of the guidance as we get closer to this weekend.

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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.

 

Since this is starting to get into the range of the NAM, here is the NAM's 0-3km CAPE values for 18z Sunday off of the 06z NAM:

 

CENTRAL_ETA212_0-3KM_CAPE_84HR.gif

 

Some of those values over Eastern Iowa and Missouri are incredible, over 200 J/kg even some spots over 300 J/kg of 0-3km CAPE.

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Very high amounts of 0-3km CAPE still remaining in place at 00z Monday, the instability doesn't look to drop off much until well after 00z as well which could potentially be worrisome if this ends up being a tornado outbreak. Nighttime tornadoes are not good especially in the fall as we have more hours of night time compared to say May/June.

 

CENTRAL_ETA212_0-3KM_CAPE_84HR.gif

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I see the GFS is still confused as to which low is going to be the main low, it tries to keep the first low as the main low until Sunday afternoon, this model though has been wildly inconsistent with its evolution of the system compared to every other model, at this point there really is no reason to be weighting a forecast toward the GFS. The Euro and other guidance have been very consistent on the first wave being weaker than the main wave for Sunday.

 

The funny thing about the GFS is that the 2nd vorticity max is by far the stronger of the 2, so the model is conflicting with itself.

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As long as the 0-3 km lapse rate remains in the 6.0 to 7.5 C/km range, a severe weather event will definitely unfold with the wind field we will have. During the halloween event, it rained in the southern Great Lakes all day and low level instability was non-existent. That doesn't look like it will be an issue this time. 

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I expected an expansion of the risk area Northward, I didn't expect it to go all the way to here though.

The 06z run of the GFS is much closer to the rest of the models, I would completely discount the 00z GFS at this point. Also this is getting into the range of the NAM now, and it is showing widespread 1000+ J/kg from Southern Wisconsin all the way down the front. You just don't see instability like that at this time of the year, and mind you that isn't even at peak heating, that is only at 18z. That would be a much more realistic thermodynamic profile with respect to this system when compared to the GFS. The ceiling for this event is already high considering the kinematics with the strong and strengthening low, adding in instability of 750-1250J/kg and things will probably go in a big way. This certainly looks to be the biggest potential this region has had all year, I also expect the GFS to correct closer to the rest of the guidance as we get closer to this weekend.

I'm probably the most concerned I've been for the region since 3/2/12 especially tornadic wise.

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The moisture is the biggest issue here I think. MLCAPE will struggle to get to 1000- mid 50s dews reside in the central GOM right now and the models show weak ridging across the coast for quite a while. If we could get low-mid 60s dews than all heck would break loose given the magnitude of the LL shear, but low 60s may be all we can hope for. The new UK  and GGEM suggest a slightly deeper trough than the GFS and NAM, so if the stronger dynamics can get farther south with deeper surface LP, then we may achieve better moisture return. In any event there should be several tornadoes, but will it be a true outbreak and will there be any strong/violent tornadoes. That is the $64 dollar question right now.

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It's the craptastic GGEM, but it jumped to the faster GFS solution now.

 

Yes it did move toward the speed of the GFS however it is not trying to have the first low be the main low until Sunday like the GFS is, also it is several millibars stronger than the GFS at the same time Sunday evening.

 

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The number 2 GFS analog for Sunday is November 10, 2002. (Veterans Day weekend tornado outbreak)

And we all agree that is the least favorable model for a tornado outbreak. hmmmmm....

It appears that 11/10/02 is actually #1 and then #3 is 11/22/10, the day of a high end EF-2 near Rockford IL and 2 EF-1 tors in southeast Wisconsin. There's several long track tornadoes amongst the 93 tornado reports in the top analogs.

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It appears that 11/10/02 is actually #1 and then #3 is 11/22/10, the day of a high end EF-2 near Rockford IL and 2 EF-1 tors in southeast Wisconsin. There's several long track tornadoes amongst the 93 tornado reports in the top analogs.

 

You are right. I was still looking at the 00Z data, but 12Z it is number 1.

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