January 28-30 Severe threat. S Plains to TN valley to SE

[Ground Scouring]

At the risk of flip-flopping several times, I'm becoming more skeptical now that instability will be sufficient for a major headline-making event. It's one thing for the GFS to show low CAPE primarily due to cool BL temps and cloud cover, but the ECMWF and NAM are very similar in their depictions of instability. Just about every model strongly suggests widespread initiation between 12-15z along the I-35 corridor. I agree with something that Tony said a few days ago: early initiation usually isn't a dealbreaker in Southeast events. But this event will (as currently modeled) be centered more over the Ozarks and Arklatex, and I believe widespread morning initiation will be quite detrimental to SigTor potential should it occur.

 

To put things into perspective, the SREF indicates no more than a 20% chance for SBCAPE exceeding 1000 J/kg over the entire warm sector Tuesday afternoon. We're within 48-60 hrs of game time, so that's difficult to ignore.

I have seen plenty of cases in which the SREF underestimated SBCAPE within 48 hours before the event, only to shift as modeling caught up with the thermodynamic picture. I would not hang my hat entirely upon SREF prognostics 48 hours out when the modeling is just beginning to latch on to the real thermodynamic picture and has yet to absorb new radiosonde and upper-air data. And as Tony posted, any increase in instability due to a drier warm sector and delayed convective initiation--relative to what is currently indicated on the NAM--would bolster lapse rates higher up in the column. What did the SREF show about 48 hours before Super Tuesday?

[tornadotony]

At the risk of flip-flopping several times, I'm becoming more skeptical now that instability will be sufficient for a major headline-making event. It's one thing for the GFS to show low CAPE primarily due to cool BL temps and cloud cover, but the ECMWF and NAM are very similar in their depictions of instability. Just about every model strongly suggests widespread initiation between 12-15z along the I-35 corridor. I agree with something that Tony said a few days ago: early initiation usually isn't a dealbreaker in Southeast events. But this event will (as currently modeled) be centered more over the Ozarks and Arklatex, and I believe widespread morning initiation will be quite detrimental to SigTor potential should it occur.

 

To put things into perspective, the SREF indicates no more than a 20% chance for SBCAPE exceeding 1000 J/kg over the entire warm sector Tuesday afternoon. We're within 48-60 hrs of game time, so that's difficult to ignore.

 

To be clear, I think instability is likely to verify higher than the ~250-600 J/kg SBCAPE painted by many models across AR. But in my view, it will have to be much higher -- widespread values of 1000-1500 J/kg -- in order for a significant outbreak of tornadic supercells to occur. Again, just based on subjective observation, I think the threshold is higher in the Ozarks than in Dixie.

 

I don't doubt the potential for several tornadoes, possibly a few significant, but I'm leaning more toward a messy/QLCS mode if initiation is focused during the morning hours. Of course, events like April 14 of last year remind us that even on strongly-forced days, convective parameterizations occasionally crap the bed completely inside of 24-48 hrs, so I'm not throwing in the towel. But from my memory, the instability progs for an event like Super Tuesday looked a good bit more impressive (at least on the NAM/ECMWF) at this range. I sure wish we could go back and look at those models for comparison, actually.

One other thing...I don't think this is the case. 

 

[CUmet]

I don't doubt the potential for several tornadoes, possibly a few significant, but I'm leaning more toward a messy/QLCS mode if initiation is focused during the morning hours. Of course, events like April 14 of last year remind us that even on strongly-forced days, convective parameterizations occasionally crap the bed completely inside of 24-48 hrs, so I'm not throwing in the towel. But from my memory, the instability progs for an event like Super Tuesday looked a good bit more impressive (at least on the NAM/ECMWF) at this range. I sure wish we could go back and look at those models for comparison, actually.

This is my recollection as well.  Obviously the GFS has changed since then, but I recall it showing max CAPE of some 1000 or so J/kg across most of AR for that event.

[chase_stormz]

One other thing...I don't think this is the case. 

 

Excellent example. If I remember correctly, of all the tornadoes that night, the one that went through springfield was and EF3?

[tornadotony]

Excellent example. If I remember correctly, of all the tornadoes that night, the one that went through springfield was and EF3?

No, that one was just E of Springfield a little while after this sounding was launched.  There was one in the QLCS around 2 AM in downtown Springfield that was EF1.

[chase_stormz]

No, that one was just E of Springfield a little while after this sounding was launched.  There was one in the QLCS around 2 AM in downtown Springfield that was EF1.

Oh okay, well my point being CAPE area wide was in that 750-1000 threshold that some of you were saying is not good enough in the Ozarks..wrong they are lol.

[tornadotony]

This is my recollection as well.  Obviously the GFS has changed since then, but I recall it showing max CAPE of some 1000 or so J/kg across most of AR for that event.

I think you guys are right, and those higher values did verify across Arkansas.

 

 

There were no values like that anywhere in the true heart of the outbreak area, though, across TN, KY, or AL, modeled or verified.

[tornadotony]

Oh okay, well my point being CAPE area wide was in that 750-1000 threshold that some of you were saying is not good enough in the Ozarks..wrong they are lol.

The thresholds are also dependent on the situation, though.  In situations with very high shear or very poor forcing, they will be higher because you'll need more buoyancy to support convection.  The key to this event is figuring out where that threshold exactly is.  We'll have some pretty wicked forcing, but we also have an enormous amount of wind shear.  I don't honestly know what the threshold is going to be.

[brettjrob]

One other thing...I don't think this is the case. 

 

That's funny; I thought of that day almost immediately after typing what I did. I certainly wouldn't be surprised to see a storm or tornado along those lines Tuesday even if CAPE is modest. But I still think that something more widespread on the scale of Super Tuesday, where you have 10 or more discrete supercells wreaking havoc over a wide area, is unlikely without doubling or tripling the current CAPE progs. IIRC, that evening we saw a few supercells training along the baroclinic zone with intense mesocyclones, but not a lot noteworthy over the open warm sector.

 

Also, regarding diurnal timing, I just can't recall something like Yazoo City (noon?) or Jackson MS 2011 (10:30am?) happening in E OK or the Ozarks -- at least since I've been paying attention. I'd be less surprised to see discrete tornadic supercells there in 500-750 J/kg SBCAPE if they developed during the evening as instability waned from its diurnal maximum, versus mid-late morning and never getting insolation at all.

[chase_stormz]

I think you guys are right, and those higher values did verify across Arkansas.

 

 

There were no values like that anywhere in the true heart of the outbreak area, though, across TN, KY, or AL, modeled or verified.

Anyone know what the sb cape values ended up being in w TN where the union ef4 occurred and across the rest of the heart of the outbreak area?

[tornadotony]

That's funny; I thought of that day almost immediately after typing what I did. I certainly wouldn't be surprised to see a storm or tornado along those lines Tuesday even if CAPE is modest. But I still think that something more widespread on the scale of Super Tuesday, where you have 10 or more discrete supercells wreaking havoc over a wide area, is unlikely without doubling or tripling the current CAPE progs. IIRC, that evening we saw a few supercells training along the baroclinic zone with intense mesocyclones, but not a lot noteworthy over the open warm sector.

 

Also, regarding diurnal timing, I just can't recall something like Yazoo City (noon?) or Jackson MS 2011 (10:30am?) happening in E OK or the Ozarks -- at least since I've been paying attention. I'd be less surprised to see discrete tornadic supercells there in 500-750 J/kg SBCAPE if they developed during the evening as instability waned from its diurnal maximum, versus mid-late morning and never getting insolation at all.

New Years 2010?  EDIT:  This has been an on and off CIPS top-15 analog too.

 

[Ground Scouring]

The thresholds are also dependent on the situation, though. In situations with very high shear or very poor forcing, they will be higher because you'll need more buoyancy to support convection. The key to this event is figuring out where that threshold exactly is. We'll have some pretty wicked forcing, but we also have an enormous amount of wind shear. I don't honestly know what the threshold is going to be.

In this case, given both dynamics and the 15°C+ 850-mb temperatures well into KY and the south half of IL, would not the MLCAPE--which will be on the order of that of Super Tuesday in this case--given surface temperatures and dew points, make more of a difference than the SBCAPE threshold? That seems to be my assessment in this case, which is why I am skeptical about excessive reliance upon the magic cut-off between 800-1000 j/g and 1500+ j/kg of SBCAPE in terms of predicting a more-widespread tornado outbreak.

Oh, okay...well, my point being CAPE-area-wide was in that 750-1000 threshold that some of you were saying is not good enough in the Ozarks...wrong they are lol.

MLCAPE has been proven to make more of a difference in some cases, I believe.

[chase_stormz]

In this case, given both dynamics and the 15°C+ 850-mb temperatures well into KY and the south half of IL, would not the MLCAPE--which will be on the order of that of Super Tuesday in this case--given surface temperatures and dew points, make more of a difference than the SBCAPE threshold? That seems to be my assessment in this case, which is why I am skeptical about excessive reliance upon the magic cut-off between 800-1000 j/g and 1500+ j/kg in terms of predicting a more-widespread tornado outbreak.

 

 

Is there anywhere you can view MLCAPE on the models?

[brettjrob]

New Years 2010?  EDIT:  This has been an on and off CIPS top-15 analog too.

 

 

Good call, that completely slipped my mind. Still, like 1/7/08, this was focused entirely along the frontal zone. I should amend my skepticism to be more specific in that I don't know we'll see numerous tornadic supercells over the warm sector if CAPE is in short supply. There is obviously precedent for big trouble along the baroclinic boundary any time of day, and with very meager instability, as you've correctly pointed out.

 

snowflake, you're thinking along the right lines, as Mesoanalysis on both 1/7/08 and 12/31/10 indicated substantially higher MLCAPE than SBCAPE at the time and location of the storms.

[tornadotony]

Good call, that completely slipped my mind. Still, like 1/7/08, this was focused entirely along the frontal zone. I should amend my skepticism to be more specific in that I don't know we'll see numerous tornadic supercells over the warm sector if CAPE is in short supply. There is obviously precedent for big trouble along the baroclinic boundary any time of day, and with very meager instability, as you've correctly pointed out.

 

snowflake, you're thinking along the right lines, as Mesoanalysis on both 1/7/08 and 12/31/10 indicated substantially higher MLCAPE than SBCAPE at the time and location of the storms.

Yeah those are both good points.  I think we may be thinking along similar lines here and maybe just not realizing it.  I pretty well agree with concerns about prefrontal convection, but I think that what does form along the front is going to be nasty.

[chase_stormz]

Yeah those are both good points.  I think we may be thinking along similar lines here and maybe just not realizing it.  I pretty well agree with concerns about prefrontal convection, but I think that what does form along the front is going to be nasty.

 

Is the baroclinic boundary the cf or the prefrontal dryline?

 

Also where can you view MLCAPE, what is being progged for this event?

[CUmet]

One thing I'm noticing is that much of the precip being depicted by the NAM, GFS, and ECMWF is located pretty close to the front itself.  There appears to be nothing initiating further into the warm sector.  This would hint at more clearing and insolation during the afternoon across parts of eastern AR and western MS/TN, which would significantly raise the surface temperatures.  This is supported by the dry patch over this region shown by the 850 mb dewpoint fields, supporting the lack of low cloud cover.  However, this also means that the moisture is quite shallow in this region, which means that due to mixing, the surface dewpoints will likely drop some, making it much more difficult for free warm sector convective initiation prior to 00z.  With that said, the moisture depth greatly improves after 00z across the warm sector, and as someone previously noted, the CAPE being progged stays constant or even slightly increases in some areas, supporting a nocturnal tornado threat.  

This upcoming event is really tricky and uncertain on a lot of levels.  The early initiation is somewhat troubling, although the models seem to hint that the storms that initiate early won't overtake the warm sector.  Although I have no doubt that the surface temps are underdone, and the actual CAPE will exceed the model forecasted CAPE, the model progs are not quite as impressive as they were for Super Tuesday.  I feel pretty confident that this will not go crazy up to historic outbreak levels (i.e. Super Tuesday), BUT the parameters are still favorable for a moderate-significant tornado outbreak to occur Tuesday evening into early Wednesday afternoon IMO.  Given the crazy shear profiles and the straddling about the "threshold CAPE" on one end, and the questions about early initiation and precip on the other, this event has more uncertainty and a a wider range of potential outcomes than most events do at the 48 hour forecast point, I think.

[tornadotony]

Is there anywhere you can view MLCAPE on the models?

http://weather.cod.edu/forecast/

 

The 00z NAM has 500-700J/kg MLCAPE over AR/W TN/N MS Tues night/Wed morn.  We'll see if that's enough.

[Ground Scouring]

One thing I'm noticing is that much of the precip being depicted by the NAM, GFS, and ECMWF is located pretty close to the front itself.  There appears to be nothing initiating further into the warm sector.  This would hint at more clearing and insolation during the afternoon across parts of eastern AR and western MS/TN, which would significantly raise the surface temperatures.  This is supported by the dry patch over this region shown by the 850 mb dewpoint fields, supporting the lack of low cloud cover.  However, this also means that the moisture is quite shallow in this region, which means that due to mixing, the surface dewpoints will likely drop some, making it much more difficult for free warm sector convective initiation prior to 00z.  With that said, the moisture depth greatly improves after 00z across the warm sector, and as someone previously noted, the CAPE being progged stays constant or even slightly increases in some areas, supporting a nocturnal tornado threat.  

This upcoming event is really tricky and uncertain on a lot of levels.  The early initiation is somewhat troubling, although the models seem to hint that the storms that initiate early won't overtake the warm sector.  Although I have no doubt that the surface temps are underdone, and the actual CAPE will exceed the model forecasted CAPE, the model progs are not quite as impressive as they were for Super Tuesday.  I feel pretty confident that this will not go crazy up to historic outbreak levels (i.e. Super Tuesday), BUT the parameters are still favorable for a moderate-significant tornado outbreak to occur Tuesday evening into early Wednesday afternoon IMO.  Given the crazy shear profiles and the straddling about the "threshold CAPE" on one end, and the questions about early initiation and precip on the other, this event has more uncertainty and a a wider range of potential outcomes than most events do at the 48 hour forecast point, I think.

This is a great analysis with which I am in much agreement (see the bolded excerpts). Do you agree, however, that if early initiation is less than indicated on the models, thereby leading to higher SBCAPE over the warm sector and steeper lapse rates higher in the column, that the event could easily rise to the occasion and allow a higher-end potential ahead of the front? Given the stronger-than-expected dry punch over MX this evening, as indicated by DRT radiosondes at 00Z, I think this scenario is likely to occur, but I would like to hear your input.

[thewxmann]

One thing I'm noticing is that much of the precip being depicted by the NAM, GFS, and ECMWF is located pretty close to the front itself.  There appears to be nothing initiating further into the warm sector.  This would hint at more clearing and insolation during the afternoon across parts of eastern AR and western MS/TN, which would significantly raise the surface temperatures.  This is supported by the dry patch over this region shown by the 850 mb dewpoint fields, supporting the lack of low cloud cover.  However, this also means that the moisture is quite shallow in this region, which means that due to mixing, the surface dewpoints will likely drop some, making it much more difficult for free warm sector convective initiation prior to 00z.  With that said, the moisture depth greatly improves after 00z across the warm sector, and as someone previously noted, the CAPE being progged stays constant or even slightly increases in some areas, supporting a nocturnal tornado threat.  

This upcoming event is really tricky and uncertain on a lot of levels.  The early initiation is somewhat troubling, although the models seem to hint that the storms that initiate early won't overtake the warm sector.  Although I have no doubt that the surface temps are underdone, and the actual CAPE will exceed the model forecasted CAPE, the model progs are not quite as impressive as they were for Super Tuesday.  I feel pretty confident that this will not go crazy up to historic outbreak levels (i.e. Super Tuesday), BUT the parameters are still favorable for a moderate-significant tornado outbreak to occur Tuesday evening into early Wednesday afternoon IMO.  Given the crazy shear profiles and the straddling about the "threshold CAPE" on one end, and the questions about early initiation and precip on the other, this event has more uncertainty and a a wider range of potential outcomes than most events do at the 48 hour forecast point, I think.

 

I've noticed this as well. Personally, I'm a little less convinced about the threat in the Ozarks than further south and east after dark, assuming the 0Z NAM has a clue. Increasing CAPEs in a nocturnal environment with roaring winds in the low-levels are good indicators for nocturnal tornado activity.

[andyhb]

I've noticed this as well. Personally, I'm a little less convinced about the threat in the Ozarks than further south and east after dark, assuming the 0Z NAM has a clue. Increasing CAPEs in a nocturnal environment with roaring winds in the low-levels are good indicators for nocturnal tornado activity.

 

People tend to forget that the January 1999 events (1/17 and, to a lesser extent, 1/21) and Super Tuesday were predominantly nocturnal tornado outbreaks.

[chase_stormz]

Very interesting write-up regarding Super Tuesday and the forecasting from the SPC leading up to the event.

 

http://www.spc.noaa.gov/publications/evans/sup-tues.pdf

[SmokeEater]

BMX has raised their tornado confidence level to 3 out of 5 for early Wednesday. Not too often do you see that scale that high 48 hrs out. Makes me think they may be worried about tornadoes being the main threat.

[David Reimer]

BMX has raised their tornado confidence level to 3 out of 5 for early Wednesday. Not too often do you see that scale that high 48 hrs out. Makes me think they may be worried about tornadoes being the main threat.

 

Their 'scale' has been at a 3 since earlier today. They mentioned in their afternoon AFD that the primary threat will be damaging straight-line winds but spinup QLCS tornadoes will also be a possibility. 

 

I hope folks are remembering to check the 3 KM CAPE values for this event. If a majority of the 500-700 J/Kg is in the lowest levels, there will be a problem. 

 

[OKpowdah]

Something else to watch ... support for nocturnal storms in E OK Monday night

[chase_stormz]

Their 'scale' has been at a 3 since earlier today. They mentioned in their afternoon AFD that the primary threat will be damaging straight-line winds but spinup QLCS tornadoes will also be a possibility. 

 

I hope folks are remembering to check the 3 KM CAPE values for this event. If a majority of the 500-700 J/Kg is in the lowest levels, there will be a problem. 

Oh, by the way, CUmet always tends to get doubtful on these winter events. He was calling bust on the Super Tuesday outbreak about 90 minutes before Memphis got slammed by two tornadic supercells. Whenever he starts to get doubtful or downplays an event, I usually start getting more concerned with it.

 

LMAO, you chasing David?

[David Reimer]

LMAO, you chasing David?

 

Nope! This isn't a chase-worthy event. I'll be in Dallas on-shift covering the social media outlets for my company. 

[chase_stormz]

Nope! This isn't a chase-worthy event. I'll be in Dallas on-shift covering the social media outlets for my company. 

 

What do you consider "chase worthy" lol?

[David Reimer]

What do you consider "chase worthy" lol?

 

Not a squall line or mini-supercells moving at 65 MPH in the hills and trees after dark. 

[chase_stormz]

Not a squall line or mini-supercells moving at 65 MPH in the hills and trees after dark. 

 

Lol my favorite Getting good at chasing AR/MS now.