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Historic Tornado Outbreak April 27, 2011


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RUC has the LLJ increasing throughout the night, with 70kts by 11Z. 0-1 Helicity above 550 in N MS/W TN and EHI of 7 over most of LA and W MS.....at 11Z........just, wow.

It's just really hard for me to believe that this is going to pan out like this. I have a difficult time believing this, but that's what the guidance keeps showing.

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I dunno, I'm a little doubtful of tomorrow. The parameters yesterday and today were pretty impressive, but both days ended up underperforming somewhat (with the exception of that freak AR tornado). In both cases, it is MHO that more tornadoes would've occurred if there weren't as many storms interfering with each other. Well, tomorrow's forcing is even stronger. Unlike the last storm, this one hasn't been a really prolific tornado producer. I could definitely see a outbreak occurring tomorrow, but I'd be a little more bearish than usual... there has been a lot of strong wording thrown around with this system that hasn't really come to fruition yet.

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Hey everyone, with so much comparison between tomorrow and 1974, thought I would post a link to the WHAS radio "right off the board" recordings of that disaster from Louisville. It's an interesting listen, if for no other reason to see the great difference between our forecasting and the forecasting then.

http://www.lkyradio....ASairchecks.htm

(SCROLL DOWN TO THE 1974 SECTION)

And to keep this on-topic, I just wanted to let you all know I'll make sure and keep you all posted on what happens in the heart of the Bluegrass tomorrow! Best wishes.

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I dunno, I'm a little doubtful of tomorrow. The parameters yesterday and today were pretty impressive, but both days ended up underperforming somewhat (with the exception of that freak AR tornado). In both cases, it is MHO that more tornadoes would've occurred if there weren't as many storms interfering with each other. Well, tomorrow's forcing is even stronger. Unlike the last storm, this one hasn't been a really prolific tornado producer. I could definitely see a outbreak occurring tomorrow, but I'd be a little more bearish than usual... there has been a lot of strong wording thrown around with this system that hasn't really come to fruition yet.

This is definitely what we've been seeing here and throughout our portion of the High Risk zone today. There has simply been too much convection for us to have a lot of tornadoes. We've had plenty of warnings, but the most prolific production in our CWA has been south and east of the high risk zone. I'm starting to think tomorrow's highest risk might be well south of where everyone thinks it will be and might be like south and central parts of AL and MS because there will be less interference with the convection that does develop.

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This is definitely what we've been seeing here and throughout our portion of the High Risk zone today. There has simply been too much convection for us to have a lot of tornadoes. We've had plenty of warnings, but the most prolific production in our CWA has been south and east of the high risk zone. I'm starting to think tomorrow's highest risk might be well south of where everyone thinks it will be and might be like south and central parts of AL and MS because there will be less interference with the convection that does develop.

Normally I would agree but the capping gradient is much stronger than it is today and the LCL's are, as usual, a little high as you go south. Ironically it will end up being greatest discrete supercell potential south of a Huntsville-Decatur line, but greatest tornado threat north. The narrow area where the two overlap slightly may end up being the "sweet spot" where the full potential of the parameters may be most well tapped.

P.S. the NAM shows a nice cold-pool stabilized region in ctrl TN at 18Z tomorrow...

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Normally I would agree but the capping gradient is much stronger than it is today and the LCL's are, as usual, a little high as you go south. Ironically it will end up being greatest discrete supercell potential south of a Huntsville-Decatur line, but greatest tornado threat north. The narrow area where the two overlap slightly may end up being the "sweet spot" where the full potential of the parameters may be most well tapped.

P.S. the NAM shows a nice cold-pool stabilized region in ctrl TN at 18Z tomorrow...

And then shows rapid destabilization during the afternoon.

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I dunno, I'm a little doubtful of tomorrow. The parameters yesterday and today were pretty impressive, but both days ended up underperforming somewhat (with the exception of that freak AR tornado). In both cases, it is MHO that more tornadoes would've occurred if there weren't as many storms interfering with each other. Well, tomorrow's forcing is even stronger. Unlike the last storm, this one hasn't been a really prolific tornado producer. I could definitely see a outbreak occurring tomorrow, but I'd be a little more bearish than usual... there has been a lot of strong wording thrown around with this system that hasn't really come to fruition yet.

A few honest points, as I do respect your opinion quite a bit.

I don't think you can say that yesterday and today underperformed (unless you were expecting a lot more). Yesterday ended up being a pretty decent outbreak with quite a few tornado reports, and today as well. The weakness of today's event (the weaker low-level wind field) was highlighted indirectly earlier, when it was stated that the timing of the trough was a bit slow, resulting in a weaker low-level response. Regardless, I am not a fan at all of the philosophy "the first day ended up underperforming, therefore the second day is more likely to underperform as well". Personally, I tend to treat every day as an independent event, because that's what they really are for the most part w.r.t severe weather. New geographic area, new instability/shear parameters, new storm mode questions, new morning precip issues, etc.

I don't think we'll have a problem of too many storms interfering with each other tomorrow. Unlike today, there is a clear focus for convective initiation, and given that the deep-layer shear vectors are perpendicular to the boundary (think April 15-16), it will ensure a sustained discrete supercell mode. There are questions regarding the extent of morning convection and its impact on the warm sector instability, but even the latest NAM run as Tony said is destablizing things very quickly following the passage of the first cluster. If there isn't a major tornado outbreak tomorrow, the morning convection is most likely going to be responsible.

Given the extreme rarity of seeing a strong mid-level 100 kt jet streak punching through a moist, unstable warm sector, with cyclogenesis ramping up the low-level wind fields and skyrocketing the helicities...the strong language used by me and many other mets regarding this event has been and is 100% justified. I try my best not to hype things up, and I'm brutally honest when I say I don't like a particular setup for reasons x,y,z. On the other hand, I know potential when I see it, and I have to be honest when I say that this might be the best outbreak setup I've seen in the dozen or so years I've been following severe weather. Whether it actually verifies that way or not, we'll just have to see...

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A few honest points, as I do respect your opinion quite a bit.

I don't think you can say that yesterday and today underperformed (unless you were expecting a lot more). Yesterday ended up being a pretty decent outbreak with quite a few tornado reports, and today as well. The weakness of today's event (the weaker low-level wind field) was highlighted indirectly earlier, when it was stated that the timing of the trough was a bit slow, resulting in a weaker low-level response. Regardless, I am not a fan at all of the philosophy "the first day ended up underperforming, therefore the second day is more likely to underperform as well". Personally, I tend to treat every day as an independent event, because that's what they really are for the most part w.r.t severe weather. New geographic area, new instability/shear parameters, new storm mode questions, new morning precip issues, etc.

I don't think we'll have a problem of too many storms interfering with each other tomorrow. Unlike today, there is a clear focus for convective initiation, and given that the deep-layer shear vectors are perpendicular to the boundary (think April 15-16), it will ensure a sustained discrete supercell mode. There are questions regarding the extent of morning convection and its impact on the warm sector instability, but even the latest NAM run as Tony said is destablizing things very quickly following the passage of the first cluster. If there isn't a major tornado outbreak tomorrow, the morning convection is most likely going to be responsible.

Given the extreme rarity of seeing a strong mid-level 100 kt jet streak punching through a moist, unstable warm sector, with cyclogenesis ramping up the low-level wind fields and skyrocketing the helicities...the strong language used by me and many other mets regarding this event has been and is 100% justified. I try my best not to hype things up, and I'm brutally honest when I say I don't like a particular setup for reasons x,y,z. On the other hand, I know potential when I see it, and I have to be honest when I say that this might be the best outbreak setup I've seen in the dozen or so years I've been following severe weather. Whether it actually verifies that way or not, we'll just have to see...

Yeah I would have to agree with all of this, I think saying tomorrow will underperform is a bit premature. If we have issues with the setup by say noon tomorrow then we can talk about the potential underperforming.

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There continue to be some very critical differences between the NAM and GFS for tomorrow. Should be an interesting day to see how things evolve.

It's these differences that will probably cause them to not pull the trigger on a high until the 2nd outlook at 1300Z if they dont at 0600Z

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There continue to be some very critical differences between the NAM and GFS for tomorrow. Should be an interesting day to see how things evolve.

The northern threat is definitely a bit tricky. The new GFS would indicate the best tornado parameters stay further south like some of the earlier NAM runs indicated. Areas of Mississippi, Alabama, Tennessee and Kentucky are definitely looking like the most likely areas for significant severe tomorrow. Further north may have a lot to do with how tonight's convection evolves. That will no doubt influence exactly if and where that secondary low develops/evolves.

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I'd agree with this. That area just looks nasty..

FoxAlabamaLive.com ... if you want to watch our live streaming coverage tomorrow guys. We will have live streaming chasers in the field, as well as giving the FasTrac, VIPIR, and GR2Analyst systems a good workout. I'll be the bald guy in the background in a white shirt and red tie. :thumbsup:

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The Northern threat area is definitely tricky. The HRRR is trying to clear things out by 14z across nearly all of Indiana with destabilization then in-progress. With the two surface low reflections, winds back pretty significantly across the Northern threat area with very high levels of low level shear, just not as much instability. Tough call really, but with the lows spinning near by and plenty of effective shear at the surface, the potential is definitely there.

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FoxAlabamaLive.com ... if you want to watch our live streaming coverage tomorrow guys. We will have live streaming chasers in the field, as well as giving the FasTrac, VIPIR, and GR2Analyst systems a good workout. I'll be the bald guy in the background in a white shirt and red tie. :thumbsup:

Good luck tomorrow Fred. I have meetings in Indpls. Wed. and Thursday and will be away from a computer grinding my teeth until I get back to the hotel to see TWC and news media reports of what's been happening.

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The above posted WRF model seems to agree with the HRRR. Looking at the amount of convection over the Mississippi Valley it's probably safe to say we're gonna see a lot of leftover convection early tomorrow. What's interesting is both the WRF and HRRR lay out an east/west boundary over central Mississippi and Alabama later tomorrow morning. This will no doubt retreat northward towards the Tennessee border by afternoon. This boundary may interact with and help enhance powerful supercells where it lays out tomorrow afternoon.

cape_sfc_f15.png

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