November 11th-12th storm system

[RCNYILWX]

I think 11/17/13 skewed perceptions of November severe weather some in terms of instability parameters. Euro is showing midlevel lapse rates of ~6.5-7C/km Weds evening over northern IL, which will likely yield enough instability for this to be a problem given the impressive wind fields/shear.

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[Hoosier]

I think 11/17/13 skewed perceptions of November severe weather some in terms of instability parameters. Euro is showing midlevel lapse rates of ~6.5-7C/km Weds evening over northern IL, which will likely yield enough instability for this to be a problem given the impressive wind fields/shear.

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Yeah, 11/17/2013 was about as impressive as it gets instability wise, especially in IL.  I can't remember seeing many (or any) November setups with that much CAPE.

[RCNYILWX]

Yeah, 11/17/2013 was about as impressive as it gets instability wise, especially in IL. I can't remember seeing many (or any) November setups with that much CAPE.

Exactly, in addition to the historical nature of the outbreak itself, another giveaway to its extreme nature was the 3"+ diameter hail produced by the supercell near BMI. That's large hail for any time of year in this region, let alone November.

This time of year, all that's really needed is adequate instability for low top supes or qlcs with embedded tors given the amount of shear, and unless this thing trends weaker as we get closer, it seems like wind fields could be as or more impressive than 11/17 with this event. I agree with your general idea on floor/ceiling with this event given overall consistency on guidance past few model cycles.

[HillsdaleMIWeather]

Exactly, in addition to the historical nature of the outbreak itself, another giveaway to its extreme nature was the 3"+ diameter hail produced by the supercell near BMI. That's large hail for any time of year in this region, let alone November.

This time of year, all that's really needed is adequate instability for low top supes or qlcs with embedded tors given the amount of shear, and unless this thing trends weaker as we get closer, it seems like wind fields could be as or more impressive than 11/17 with this event. I agree with your general idea on floor/ceiling with this event given overall consistency on guidance past few model cycles.

 

Definitely agreed there, I see a lesser tornado threat than 11/17 but if this thing cotinues to trend upwards with instability, we could have a major severe wind threat. 

[ClicheVortex2014]

One of the 3/2/12 supercells tracked into an area with very low instability in WV while still producing a strong tornado, but it developed in an area of higher CAPE initially.

That's a good point... but I don't think it really got far. The SRH was just off the charts at the time... effective SRH was >1100... 0-1km SRH was >800. With that kind of increasing spin, I wouldn't expect it to just magically pick up off the ground as soon as the updraft got weaker. I think that was quite a special case. That whole event was special.

[andyhb]

I think 11/17/13 skewed perceptions of November severe weather some in terms of instability parameters. Euro is showing midlevel lapse rates of ~6.5-7C/km Weds evening over northern IL, which will likely yield enough instability for this to be a problem given the impressive wind fields/shear.

Sent from my SM-G900V

 

I remember mentioning how cold the 500 mb temps were going to be with that one. We had seasonably steep mid level lapse rates blended with seasonably impressive low level moisture and that's going to result in bedlam most times combined with the magnitude of shear that event had.

 

[cyclone77]

Euro is showing 65-70kts at H9 Wednesday evening behind the departing low over eastern NE into southern Iowa.  That's extremely impressive to say the least.  Could be some very impressive wind gusts in that area.

 

GFS is also suggesting a very impressive secondary burst of wind Thursday evening with the main surge of CAA.  Better mixing profiles compared to Wed evening as well.  Wouldn't be surprised to see some areas see higher winds with this batch of winds compared to the main event 24hrs before.

[ClicheVortex2014]

ILN's AFD sounds pretty good

 

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE MID LEVEL FLOW AT MID WEEK WILL BE CHARACTERIZED BY HIGH
AMPLIFICATION WITH DEEPENING UPPER LEVEL LOW LIFTING NE THRU THE
PLAINS INTO THE UPPER MS VLY. DEEP SFC LOW TO FURTHER DEEPEN AND
TRACK FROM THE CENTRAL PLAINS INTO THE UPR MS RIVER VALLEY BY
WEDNESDAY EVENING. NUMERICAL MODEL SOLNS CONTINUE TO TREND SLOWER
WITH ONSET OF PRECIPITATION. EXPECT WED TO REMAIN DRY THRU MOST OF
THE DAY WITH PCPN DEVELOPING WEDNESDAY NIGHT AHEAD OF STRONG COLD
FRONT.

ON WARM SIDE OF SYSTEM EXPECT WEDNESDAYS HIGHS TO BE CLOSE TO
10 DEGREES ABOVE NORMAL...RANGING FORM THE LOWER/MID 60S NORTH TO
THE UPPER 60S SOUTH.

HIGH SHEAR LOW CAPE EVENT MAY DEVELOP LATE WED NIGHT/EARLY THURSDAY
WITH SHERB PARAMETER CONTINUING TO POINT TOWARD THIS SIGNAL. 65 TO
70 KT 850MB LOW LEVEL JET HELPS ADVECT GULF MOISTURE NORTH AHEAD OF
THIS FRONT WEDNESDAY NIGHT WITH PW PLUME APPROACHING 1.3 INCHES.

GIVEN VERY STRONG DYNAMICS...STRONG WINDS WILL BE POSSIBLE WITH THIS
EVENT. MOMENTUM TRANSFER TECHNIQUE APPLIED TO GFS FCST
SOUNDINGS...YIELDS GUSTS INTO THE 40 KT RANGE OUTSIDE OF CONVECTION.
HAVE CONTINUED CATEGORICAL POPS FOR THIS PERIOD AND WILL INCLUDE
MENTION OF CHANCE OF THUNDER.

 

[HillsdaleMIWeather]

18Z NAM looking good, good instability.

[HillsdaleMIWeather]

18Z NAM has better wind fields as well.

[Geos]

78hr surface and 850mb shear. NAM

 

 

 

81hr

 

 

81hr 925mb winds.

 

[Hoosier]

Exactly, in addition to the historical nature of the outbreak itself, another giveaway to its extreme nature was the 3"+ diameter hail produced by the supercell near BMI. That's large hail for any time of year in this region, let alone November.

This time of year, all that's really needed is adequate instability for low top supes or qlcs with embedded tors given the amount of shear, and unless this thing trends weaker as we get closer, it seems like wind fields could be as or more impressive than 11/17 with this event. I agree with your general idea on floor/ceiling with this event given overall consistency on guidance past few model cycles.

 

 

Good point as far as the wind field comparison with 11/17.  Instability won't be as good overall but it seems like the low level flow may be backed a bit more this time around.  The surface low on 11/17 bombed later than what this is progged to do.  Check it out:

 

 

http://www.spc.noaa.gov/exper/archive/event.php?date=20131117

[Hoosier]

These forecast soundings are pretty impressive.  Just looking around, some with 0-6 km shear progged near 100 kts.

[ClicheVortex2014]

Here's the best soundings I've seen so far... NE KS and then near the MO/IL/IA border:

 

 

 

Then it transitions to the HSLC portion of the event

 

West Indiana:

 

[HillsdaleMIWeather]

18Z GFS more windy, about the same cape.

[Hoosier]

 

West Indiana:

 

 

 

You mean western Illinois. 

[TugHillMatt]

On another note, we MIGHT be able to get some snow showers off the lake here in West Michigan on Friday.

[Hoosier]

Will have to see what it looks like as it gets closer but there are signals for multiple initiating boundaries/rounds of storms, especially on the NAM. 

[bdgwx]

Some of these 18Z NAM soundings are actually pretty impressive. The Quincy, IL soundings, for example, are showing 200-300 j/kg of 3km CAPE in the presence of 30-40 kts of 1km shear with 300m LCL heights.

[IllinoisWedges]

Since most of you are using the skew-t and hodographs, this new site just came out and uses SHARPpy. Just thought I'd put it out there since no other site that I know of has it. 

 

Link: http://www.pivotalweather.com/    

 

No, I don't own it. Just thought since this event was coming near, this would be a nice addition for some of you. Anyways, the NAM has a nice plume of MUCAPE over Illinois on Wed. Of course, this will probably all change in 5 hours. 

[ClicheVortex2014]

You mean western Illinois. 

Ah yes, one of those "I-states"

[andyhb]

Some of these 18Z NAM soundings are actually pretty impressive. The Quincy, IL soundings, for example, are showing 200-300 j/kg of 3km CAPE in the presence of 30-40 kts of 1km shear with 300m LCL heights.

 

This would be more than enough to pull significant tornadoes out of these low topped storms/supercells.

[RCNYILWX]

Good point as far as the wind field comparison with 11/17. Instability won't be as good overall but it seems like the low level flow may be backed a bit more this time around. The surface low on 11/17 bombed later than what this is progged to do. Check it out:

http://www.spc.noaa.gov/exper/archive/event.php?date=20131117

Definitely even more pronounced isallobaric response being modeled. The backed flow will keep the shear vector sufficiently orthogonal to the cold front. Not sure what storm mode will be, but in favor of at least mixed mode is the orientation of the shear vector and very strong upper level jet winds. Suppose strong forcing could cause things to quickly go linear though.

[bdgwx]

Since most of you are using the skew-t and hodographs, this new site just came out and uses SHARPpy. Just thought I'd put it out there since no other site that I know of has it. 

 

Link: http://www.pivotalweather.com/    

 

No, I don't own it. Just thought since this event was coming near, this would be a nice addition for some of you. Anyways, the NAM has a nice plume of MUCAPE over Illinois on Wed. Of course, this will probably all change in 5 hours. 

 

Very cool. I just bookmarked it.

[Gilbertfly]

Great stuff on severe aspects posters

Here are some DVN nuggets on non thunderstorm wind potential...

AS THE SYSTEM LOOKS TO ROLL NORTHEAST ACRS WI AND VERTICALLY STACKS

INTO THU MORNING...AFTER WHAT EVER CONVECTION CAN MAKE IT ACRS THE

CWA AND EXIT OFF TO THE EAST...THE MAIN WEATHER STORY WILL BECOME

VERY STRONG WINDS RAMPING UP LATE WED NIGHT INTO THU. THE 12Z GFS

CONTINUES TO BACK OFF ON LLVL CYCLONIC PRESSURE GRADIENT TIGHTNESS

AND WIND SPEED...AND NOW AGREES WITH THE ECMWF THAT WINDS MORE IN

LINE OF A SOLID ADVISORY MAY UNFOLD DURING THIS PERIOD AS OPPOSED TO

IT/S EARLIER HIGH WIND WARNING CRITERIA IT WAS ADVERTISING. RIGHT

NOW IT LOOKS LIKE SUSTAINED 25 TO 35 MPH WITH GUSTS UP TO 45 AT

LEAST. BUT WITH AN INTENSE LOW STILL DEEPENING SOME OFF TO THE

NORTHEAST...MAY HAVE TO KEEP SOME GRAVITY WAVE PHENOMENA OCCURRENCE IN

MIND FOR EVEN HIGHER GUSTS. WRAP AROUND RAIN ALONG AND NORTH OF I80

LATE WED NIGHT AND INTO THU MORNING...WITH IN-WRAPPING LLVL COLD

CONVEYOR POTENTIALLY ADVECTING TEMPS IN THE 30S TO LOW 40S ACRS MUCH

OF THE CWA BY SUNRISE THU. VERY WINDY RAW DAY THU WITH HIGHS IN THE

40S TO LOWER 50S.

[andyhb]

ILX with some pretty strong wording here...

 

The main weather system will begin to move out of the southwest US
Tuesday night and bring stronger return flow to the area for
Wednesday. Models look very similar and have been consistent now for
the past several runs so that confidence is high that an outbreak of
severe weather will be possible somewhere in the middle part of the
Miss river valley. The forecasted track of the low pressure area
remains northwest of the state with most models moving it across IA.
Models have also slowed some with the onset of pcpn and the timing
of the cold front coming through the area on Wednesday/Wednesday
night. Current indications/forecast look to point to showers and
storms developing ahead of the front west of the area and then
quickly moving northeast into western IL Wed afternoon and then
through the eastern parts of IL Wed evening, with most of the pcpn
east and north of the area by midnight. This system still looks to
be negatively tilted with a strong low and mid level jet nosing into
the mid Miss valley Wed afternoon.

Sfc dwpts will rise into the mid to upper 50s across the area with
60 dwpts nosing into southwest IL. This should lead to CAPEs of 500-
1000 j/kg by late afternoon in western IL. Also see that the strong
low and mid level winds will support 0-6km bulk shear values of 70-
80kts with 0-3km shear of over 45kts. So believe supercells will be
likely. Storms will also be moving quickly to the northeast through
the late afternoon and evening hours. Based on other parameters at
this early stage suggest severe weather is very possible and agree
with SPCs assessment of damaging winds and possible tornadoes during
that time period. As mentioned yesterday, Nov is the mini-max period
for tornadoes in our area and many outbreaks have occurred during
the month of Nov. Still some uncertainty as this event is still
several days away, so changes in the timing and location of the
severe weather is likely to change.

[Hoosier]

ILX with some pretty strong wording here...

 

 

I don't know how I forgot about ILXs afd.  I probably read every other one from the region. 

 

Personally I'm on the "outbreak of some kind" bus.  Just bouncing around thoughts in my head, I'm wondering if realizing the greater instability out in IA/western IL etc is going to be a key in this event -- not only there, but by having ramifications downstream in areas that aren't progged to have as much.  Get things going out west and they may be able to sustain given the very strong shear/forcing...like what was mentioned earlier about 3/2/2012.

[IllinoisWedges]

Think LOT will ever mention severe weather like ILX has been doing? 

[andyhb]

Think LOT will ever mention severe weather like ILX has been doing? 

 

Considering they aren't really in the main threat zone with this (yet), I don't see why they really should.

[Stebo]

Think LOT will ever mention severe weather like ILX has been doing? 

It is a bit early for them as it is a bit more conditional that far Northeast, they are hitting the winds though at this point which makes more sense.