April 12 Severe Event

[a5ehren]

Spann has a different job than being technically correct on minor details that only weenies care about. He can’t just casually invoke 4/27/11 because people will flip their lids.

He is absolutely right to phrase things the way he did, and I can’t imagine any reason why arguing semantics is worth the time for either of you.

[sakau2007]

11 minutes ago, a5ehren said:

Spann has a different job than being technically correct on minor details that only weenies care about. He can’t just casually invoke 4/27/11 because people will flip their lids.

He is absolutely right to phrase things the way he did, and I can’t imagine any reason why arguing semantics is worth the time for either of you.

I think saying things like "Events like that happen once every 40 years" goes past being a minor detail. Also, saying April 27, 2011 is not showing up on the CIPS analogs is just... wrong. Out of what... 20,000+ days it has shown up as like the 4th, and 7th "best" analog on various runs. 

I'm with you that the overall tone of the post is correct. And that for every 50 high risk days, maybe only one will come together just perfect for a 1974/2011 type outbreak. And I do agree with you that he has a nearly impossible job of toeing the line between making people aware without worrying the weather-ignorant public unnecessarily. 

An analogy I would give is that the US coastline gets struck by a category 5 once every 30-40 years or so on average. If a cat 4 is churning in the Gulf where a favorable environment exists, it would be foolish to say "This won't be like Michael or Camille because events like that only happen once every few decades and it was just a couple of years ago since Michael". The parameters in MS are absolutely in April 27th territory. Now, obviously a lot can go "wrong" between now and then... but to use time between events as a reason that event A will not be like event B is just another take on the gambler's fallacy. 

[jpeters3]

7 hours ago, jojo762 said:

00z CAMs were a mixed bag of results... Here is a run down, with some of my own thoughts on what each solution would result in.

HRW WRF-NSSL

Storms fire early in Eastern Texas, partially associated with a long-lived complex, they continue east-northeastward over the threat are with a mixed bag of storm modes, numerous UH tracks associated with this initially activity as it traverses Louisiana and Mississippi. Numerous other supercells fire in the main threat area. This solution likely yields a tornado outbreak of some extent.

HRW NMMB

Storms fire early in Eastern Texas, traverse Louisiana and into the main threat area... WAA activity explodes across the warm sector, still some hints of severe supercells embedded within this activity, but overall mutes most of the threat across Mississippi/Alabama... Meanwhile numerous discrete cells pop across Arkansas, possibly yielding a more localized tornado outbreak there. In relation to the WAA activity, from my own experience of using the NMMB, it does seem to frequently overconvect.

HRW WRF-ARW

Probably the scariest of the bunch... Storms fire early in Eastern Texas and remain mostly discrete/semi-discrete as they scream east-northeastward, numerous other discrete supercells fire in the open warm sector across large parts of Louisiana, Arkansas, Mississippi, and Alabama. This solution definitely produces a big-time tornado outbreak.

NAM NEST

Similar to every other solution, storms fire very early in the period over Eastern Texas and traverse Louisiana, essentially becoming a big blob by the time they reach Mississippi. Throughout the afternoon WAA convection is persistent across Mississippi and Alabama, with the chance for embedded supercells. By late afternoon several supercells are firing, embedded within clusters, in Arkansas with other cells trying to get going further down the front and in the open warm sector in Mississippi. Sunday night features what would likely be a dangerous QLCS over Tennessee. Unsure what this type of scenario would result in, but best guess is several tornadoes, and a ton of severe wind reports.

 

Imagine SPC will stick with a MDT risk for the 06z Day 2 SWO. 00z CAMs didn't do much to help squash the uncertainties that have been spoken about at length on twitter, this board, etc... If SPC takes credence in the idea of WAA convection persisting in the warm sector, we certainly will not get a high risk in a couple hours... If they do not put much faith in that solution, then we would probably see a high risk given the preponderance of evidence from every other model.

 

 

Good assessment of the different runs here.  It's pretty frustrating to have such a mixed-bag of solutions at this point, especially when the global models are in good agreement!

Another interesting thing to note: the modeled depictions of the warm sector parameters are quite different among these runs.  This is probably at least partially due to the different solutions for the distribution of convection through the warm sector, but I suspect something else is going on as well.  The runs that are more geared toward a tornado outbreak actually have considerably less coverage of high 0-1 km SRH in the warm sector, even prior to widespread convective converge.  Not sure why this is, or if it is even that important, but it is an interesting (and somewhat inexplicable difference).

[sakau2007]

My overall concern for this event continues to grow. I know the parameters aren't exactly the same, but this is as close to April 27, 2011 as I've seen since April 27, 2011 for MS/AL.

Just look at these STP values and tell me that doesn't bring back memories. Makes me shudder:

 

I get not wanting to be hyperbolic, but at this point emphatically saying this won't be like April 27, 2011 seems to be borderline irresponsible, no? And let's not forget this event looks like there will be prior convection. Some of the radar loops look eerily similar to me showing earlier rounds of convection that we aren't overly concerned about followed by outrageously high STP's later in the day. That is.... exactly what we were staring at on April 27 and the result was absolutely disastrous. The early morning event across Alabama was absolutely underwarned for until the event was occurring. I don't think the atmospheric paramaters were expected to be off the charts that morning (just as they aren't this time around) yet there were still dozens of tornadoes and a vicious line of storms. What is the risk something like that, even on a smaller scale, occurs? I haven't really heard that mentioned at all.

[jpeters3]

38 minutes ago, sakau2007 said:

My overall concern for this event continues to grow. I know the parameters aren't exactly the same, but this is as close to April 27, 2011 as I've seen since April 27, 2011 for MS/AL.

Just look at these STP values and tell me that doesn't bring back memories. Makes me shudder:

 

I get not wanting to be hyperbolic, but at this point emphatically saying this won't be like April 27, 2011 seems to be borderline irresponsible, no? And let's not forget this event looks like there will be prior convection. Some of the radar loops look eerily similar to me showing earlier rounds of convection that we aren't overly concerned about followed by outrageously high STP's later in the day. That is.... exactly what we were staring at on April 27 and the result was absolutely disastrous. The early morning event across Alabama was absolutely underwarned for until the event was occurring. I don't think the atmospheric paramaters were expected to be off the charts that morning (just as they aren't this time around) yet there were still dozens of tornadoes and a vicious line of storms. What is the risk something like that, even on a smaller scale, occurs? I haven't really heard that mentioned at all.

I think the point is that the chances of a repeat of April 27, 2011 are very small.  Events like this are more than just parameters.  There are a lot of things that need to come together to cause an outbreak like April 27.  Miss one piece of the puzzle, and you can end up with a marginal event at best despite off-the-charts parameters (5-20 is a classic example of this, but there have been several over the past few years).  And there are already indications that some of those things won't come together this time (questions about storm mode, etc).  So if we "sound the alarm" and tell people this will be comparable to April 27, 2011, when in reality the probability of this happening is extremely low, we lose credibility as forecasters.  I would put the chances of something comparable to that day at 5%, at best.  Especially given that parameters look to be a tad smaller than 4-27 among the consensus of guidance on top of all the uncertainties.

[SmokeEater]

It's not irresponsible, he's completely conveying how dangerous this event could be. He's never once poo poo'd it, if anything, if you watch his videos, he's being very bullish. Hell, last night he said in a video he thought a high risk upgrade was coming on the Day 2. He has to walk a very thin line right now, with what's going on in the world today and PTSD from April 27th. If you start screaming it's April 27th all over again, you'll have people so scared they won't even be able to think rationally when the event starts and warnings start coming out. Enough acting like he's damn near being negligent, he's getting out what needs to get out.

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[SmokeEater]

Just this alone even shows it, I've never seen him go that high, 2 1/2 days out from an event. That was from yesterday.

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[jjwxman]

On 4/9/2020 at 9:17 PM, Buddy1987 said:

More I look now more the parameters are the highest I’ve seen in some time for 0-1 helicity being 450-500 on the NAM and winds ripping right above the surface over 60 knots based on the GFS. Temps get close to 70. Question for the pros would be are we looking more at high shear low instability environment or do we have a chance to build up anything before everything comes together.

Most of the modeling data has surface CAPE established by early Monday morning.  Some of the modeling data is slowing the system a bit further into Monday in the Carolinas and Virginia, that would allow for even more time for destabilization.  

[TampaTwo]

57 minutes ago, sakau2007 said:

My overall concern for this event continues to grow. I know the parameters aren't exactly the same, but this is as close to April 27, 2011 as I've seen since April 27, 2011 for MS/AL.

Just look at these STP values and tell me that doesn't bring back memories. Makes me shudder:

 

I get not wanting to be hyperbolic, but at this point emphatically saying this won't be like April 27, 2011 seems to be borderline irresponsible, no? And let's not forget this event looks like there will be prior convection. Some of the radar loops look eerily similar to me showing earlier rounds of convection that we aren't overly concerned about followed by outrageously high STP's later in the day. That is.... exactly what we were staring at on April 27 and the result was absolutely disastrous. The early morning event across Alabama was absolutely underwarned for until the event was occurring. I don't think the atmospheric paramaters were expected to be off the charts that morning (just as they aren't this time around) yet there were still dozens of tornadoes and a vicious line of storms. What is the risk something like that, even on a smaller scale, occurs? I haven't really heard that mentioned at all.

The 6Z NAM SigTor values are no better than half of what was indicated on the 4/27/11 image, so I think that fits with what I am expecting with this system, which is about half of the impact of 4/27....and maybe more impactful for Mississippi than Alabama.

[TampaTwo]

if you will forgive my 5th-grade looking art work, this is my first call of how I think the SPC watch boxes will pop out tomorrow, based on the early CAMs and storm pacing. 

[DanLarsen34]

 

[jjwxman]

14 minutes ago, TampaTwo said:

The 6Z NAM SigTor values are no better than half of what was indicated on the 4/27/11 image, so I think that fits with what I am expecting with this system, which is about half of the impact of 4/27....and maybe more impactful for Mississippi than Alabama.

I believe the algorithms used to determine the STP are different among different model websites.  Pivotal weather in  my opinion has a more realistic outcome with STP in the 5-7 range (which is still really significant) across MS/AL/S TN.  Other pages such as COD Meteorology and WeatherBell have the STP in the 12-15 range which is just off the charts, but maybe a bit misleading as well? 

 

[Bob's Burgers]

Just now, jjwxman said:

I believe the algorithms used to determine the STP are different among different model websites.  Pivotal weather in  my opinion has a more realistic outcome with STP in the 5-7 range (which is still really significant) across MS/AL/S TN.  Other pages such as COD Meteorology and WeatherBell have the STP in the 12-15 range which is just off the charts, but maybe a bit misleading as well? 

 

PW will show different STP numbers (usually conservative compared to NSHARP), whereas COD is the exact opposite. I believe COD uses a different STP equation than NSHARP/SPC

[jpeters3]

Just now, jjwxman said:

I believe the algorithms used to determine the STP are different among different model websites.  Pivotal weather in  my opinion has a more realistic outcome with STP in the 5-7 range (which is still really significant) across MS/AL/S TN.  Other pages such as COD Meteorology and WeatherBell have the STP in the 12-15 range which is just off the charts, but maybe a bit misleading as well? 

 

Pretty much all the available sites do not plot maps of STP correctly.  Most show fixed layer STP, when they should really show effective layer STP.  I've also noticed large discrepancies between what is shown in SHARPpy soundings and what is shown on the map.  I trust the soundings more-so than the maps, and maximum values i've seen are in the 6-9 range.

[Bob's Burgers]

Evolution of the Baron 3km WRF solution as presented by James Spann this morning -->

 

 

[jpeters3]

7 minutes ago, DanLarsen34 said:

 

This is a tough call, but avoiding large groups in shelters which will almost certainly lead to additional covid infections in favor of a probably comparatively statistically unlikely outcome of a tornado hitting a given location seems like a good tradeoff to me.

[Sydney Claridge]

The CIPS Analogs now place 4/27/2011 as the 3rd best analog.  3/1/2007 (day of the Enterprise tornado) is the 2nd best analog; previous analog runs have consistently placed the 3/1 outbreak near the top.

Even as one of the top analogs, it does not mean this this potential tornado outbreak will be like 4/27/11, but the fact that this is showing up so high in the analog list gives us an idea what the worst-case scenario for tomorrow could be.  SPC held off on a Day 2 High Risk for 4/27/11 as well, citing concerns about morning convection, although the Day 2 Moderate went all the way up into Ohio (and as we know, that morning convection, although quite severe itself, did seem to suppress severe storms from western TN northwards and kept those northern areas from suffering an outbreak like 4/3/1974).

Just because something is the worst-case scenario does not mean it will actually occur.  But emergency management, hospitals, and public health authorities need to be ready for that worst-case scenario, especially when the risks for displaced and/or injured people involve more than just losing a home or having injuries treated at a hospital; the ongoing COVID-19 pandemic means that there is very real risk that any displaced and/or injured individuals could catch and/or spread the virus.  And as previously mentioned, even sheltering from a tornado in a public shelter could pose some concerns with respect to viral spread.  Even if this winds up not being a widespread tornado outbreak, it takes only one tornado going through a highly-populated area (and I mean anything from a moderately-sized city like Meridian MS all the way up to a major metropolitan area like Birmingham) to make these concerns real.  While absolutely devastating to the people living there, a tornado strike on a rural area or smaller town should be much more manageable for emergency management, hospitals, and public health authorities, provided that there is adequate hospital coverage and availability (that said, this can be an issue in parts of the South).

[DanLarsen34]

17 minutes ago, jpeters3 said:

This is a tough call, but avoiding large groups in shelters which will almost certainly lead to additional covid infections in favor of a probably comparatively statistically unlikely outcome of a tornado hitting a given location seems like a good tradeoff to me.

I think you’re right. Let’s just hope we don’t have to deal with this affecting people’s lives either way. 

[jpeters3]

2 minutes ago, DanLarsen34 said:

I think you’re right. Let’s just hope we don’t have to deal with this affecting people’s lives either way. 

Yeah.  A tornado outbreak on top of a pandemic starts to sound like a SCI-FI channel mini-series plotline...

[jpeters3]

Another CAM solution to add to the mix.  HRRR seems to air more toward the "outbreak" end of the spectrum by 2100 UTC, with numerous apparently discrete supercells developing over northern LA, MS, and SE AR in the high-parameter part of the warm sector.

Edit: The end of the run is still sort of a mixed bag.  Somewhere between the higher end and lower end solutions.  Probably a regional outbreak with a few strong tornadoes.

[TellicoWx]

9 minutes ago, BrandonC_TX said:

The CIPS Analogs now place 4/27/2011 as the 3rd best analog.  3/1/2007 (day of the Enterprise tornado) is the 2nd best analog; previous analog runs have consistently placed the 3/1 outbreak near the top.

Even as one of the top analogs, it does not mean this this potential tornado outbreak will be like 4/27/11, but the fact that this is showing up so high in the analog list gives us an idea what the worst-case scenario for tomorrow could be.  SPC held off on a Day 2 High Risk for 4/27/11 as well, citing concerns about morning convection, although the Day 2 Moderate went all the way up into Ohio (and as we know, that morning convection did suppress severe storms from TN northwards and kept those northern areas from suffering an outbreak like 4/3/1974).

Just because something is the worst-case scenario does not mean it will actually occur.  But emergency management, hospitals, and public health authorities need to be ready for that worst-case scenario, especially when the risks for displaced and/or injured people involve more than just losing a home or having injuries treated at a hospital; the ongoing COVID-19 pandemic means that there is very real risk that any displaced and/or injured individuals could catch and/or spread the virus.  And as previously mentioned, even sheltering from a tornado in a public shelter could pose some concerns with respect to viral spread.  Even if this winds up not being a widespread tornado outbreak, it takes only one tornado going through a highly-populated area (and I mean anything from a moderately-sized city like Meridian MS all the way up to a major metropolitan area like Birmingham) to make these concerns real.  While absolutely devastating to the people living there, a tornado strike on a rural area or smaller town should be much more manageable for emergency management, hospitals, and public health authorities, provided that there is adequate hospital coverage and availability (that said, this can be an issue in parts of the South).

Being the Fire Capt. at the time for a town here in SE TN...the morning convection spawned several touchdowns here on 4/27. It also did little to suppress the evening convection as it moved thru. Spent half the night going house to house doing search and rescue in the middle of the storms.

[1900hurricane]

2 hours ago, jpeters3 said:

Good assessment of the different runs here.  It's pretty frustrating to have such a mixed-bag of solutions at this point, especially when the global models are in good agreement!

Another interesting thing to note: the modeled depictions of the warm sector parameters are quite different among these runs.  This is probably at least partially due to the different solutions for the distribution of convection through the warm sector, but I suspect something else is going on as well.  The runs that are more geared toward a tornado outbreak actually have considerably less coverage of high 0-1 km SRH in the warm sector, even prior to widespread convective converge.  Not sure why this is, or if it is even that important, but it is an interesting (and somewhat inexplicable difference).

At the risk of sounding like a total nutjob, what if the very high 0-1 km SRH in the lesser outcome models is a sign of a poorly mixed boundary layer where the surface remains largely uncoupled from the low level jet? It seems counterintuitive, but if the low level jet and surface aren't coupled, surface winds would be lower and 0-1 km SRH would increase. The ARW/NSSL WRFs from 00Z all show low level winds closer in vector to the low level jet than the 3km NAM and NMMB of the same suite, which have weaker winds with a stronger easterly component. That however leaves the question of why the boundary layer wouldn't be mixing. Maybe low level lapse rates have something to do with it. It's a highly anecdotal case, but January 10th, 2020 was a day that had a very strong low level jet, massive 0-1 km SRH, enough instability at face value, but poor low level lapse rates across Texas (sounding below). Storms were largely elevated and messy that day. Again, highly anecdotal and far from anything scientifically sound, but maybe something to watch.

 

[Sydney Claridge]

12 minutes ago, TellicoWx said:

Being the Fire Capt. at the time for a town here in SE TN...the morning convection spawned several touchdowns here on 4/27. It also did little to suppress the evening convection as it moved thru. Spent half the night going house to house doing search and rescue in the middle of the storms.

I knew southern Tennessee was within the outbreak area on 4/27/2011 (the afternoon and evening storms were especially intense in SE TN), and was aware that the morning convection did result in multiple tornado touchdowns.  But notice the relative lack of severe storm reports from western TN up through OH, all areas that were in the Day 2 Moderate risk.  It is these areas I was saying had their severe storm potential suppressed (but not completely so, given some wind/isolated tornado reports particularly in KY/OH) by earlier convection.  I cited the Day 2 outlook from April 26, 2011 to highlight some of the concerns SPC had then with issuing a Day 2 High Risk.

[buckeyefan1]

I just want to interrupt for a brief second, to say thanks to everyone for the excellent conversations over the past few days. It's been an absolute pleasure reading these discussions while also learning a thing or two  now back to your regularly scheduled program 

[jpeters3]

16 minutes ago, 1900hurricane said:

At the risk of sounding like a total nutjob, what if the very high 0-1 km SRH in the lesser outcome models is a sign of a poorly mixed boundary layer where the surface remains largely uncoupled from the low level jet? It seems counterintuitive, but if the low level jet and surface aren't coupled, surface winds would be lower and 0-1 km SRH would increase. The ARW/NSSL WRFs from 00Z all show low level winds closer in vector to the low level jet than the 3km NAM and NMMB of the same suite, which have weaker winds with a stronger easterly component. That however leaves the question of why the boundary layer wouldn't be mixing. Maybe low level lapse rates have something to do with it. It's a highly anecdotal case, but January 10th, 2020 was a day that had a very strong low level jet, massive 0-1 km SRH, enough instability at face value, but poor low level lapse rates across Texas (sounding below). Storms were largely elevated and messy that day. Again, highly anecdotal and far from anything scientifically sound, but maybe something to watch.

 

I don't think you are a nutjob at all.  This is quite possibly an explanation for the different solutions.  

[Bob's Burgers]

Interesting NAM3k solution overnight in Alabama 

[SnowGoose69]

1 minute ago, Bob's Burgers said:

Interesting NAM3k solution overnight in Alabama 

The overnight threat I think may be getting missed somewhat.  For AL in particular but I think even GA might see a violent squall line overnight.  I don’t see much argument for this weakening as it crosses through.  Especially since it appears GA could break out into sun for awhile Sunday afternoon which could destabilize things further 

[jpeters3]

3 minutes ago, SnowGoose69 said:

The overnight threat I think may be getting missed somewhat.  For AL in particular but I think even GA might see a violent squall line overnight.  I don’t see much argument for this weakening as it crosses through.  Especially since it appears GA could break out into sun for awhile Sunday afternoon which could destabilize things further 

Depending on where you pick a sounding overnight in AL, the environment is going to be on the borderline of being supportive for violent tornadoes.  There is the issue of lacking buoyancy below 3 km, but relatively off-the-chart wind profiles.  It's also a bit hard to interpret whether the 3 km NAM is depicting supercells, or junkvection with embedded spin-ups.  But I agree, AL is certainly in play in the late evening/overnight, along with central TN.

[AmericanWxFreak]

Is tornado chasing essential? 

 

[SnowGoose69]

10 minutes ago, AmericanWxFreak said:

Is tornado chasing essential? 

 

The majority of the states/areas of those states where you’d chase this early in the season don’t really have severe enough outbreaks that anyone would really care.  It’s probably not smart though to travel in groups of 7 in vans