Tn Valley Severe Weather

[dwagner88]

18 hours ago, Wurbus said:

I live probably about 2 miles north of where the Tornado went through and had no idea it was happening at the time. Luckily, the wind wasn't too bad at my house, we just received around 1.2" of rain in about 20 minutes.

Nobody knew it was happening. It was a rare miss by MRX. No warning was issued.

[nrgjeff]

Catching up, what a week. Yes @Dsty2001 I believe that's a wall cloud on the previous page. While it looks scuddy, a likely collar cloud leading into it is the giveaway. Indeed, the whole feature is probably a wall cloud.

Does anyone have saved radar data from the Knoxville tornado? Especially the few minutes leading up to the event. We had a power outage in Chattanooga at the time, so my focus was elsewhere.

Looking at TODAY, a boundary sits across Tennessee from northwest to southeast. Boundary should focus any MCS and line segments. Perhaps closer to Arkansas the boundary can enhance SRH. Down by Chatanooga I think it's just good to promote straight line winds. Storm mode should be more conductive where SPC has the 10%. Though I doubt much will be visible if it's HP.

Some of the CAMs have beefy blobs, which could contain hail. We are truly having April in August. Storm mode does favor MCS (summer) but the jet stream and hail are out of season.

[*Flash*]

Great analysis by Convective Chronicles regarding today's threat: 

 

[*Flash*]

Based on latest radar trends, I'm curious to see if any semi-discrete cells will make into the mid-state and how long the windows for rounds 1 and 2 end up being. Right now for round 1, the potential for an over-clustered situation is there with a mostly messy storm mode. Seems like it will be less eventful compared to the overnight action. If I'm chasing, I'm more interested in areas south of 40 where cellular modes will be more consistent. Whatever the case, it certainly does not feel like August out there. 

[PowellVolz]

Some #’s from the SPC meso page for East TN
Super cell composite up to 16
Bulk wind shear effective up to 50kts
CAPE - 2500 to 3500
Helocity 100-200 depending on which layer you look at
Sig Tor is up to 3

Where is this page? Link?


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[PowellVolz]

Nobody knew it was happening. It was a rare miss by MRX. No warning was issued.

I was closely watching the radar when that tornado dropped and there was no signs at all that tornado was about to happen. Shear was barely good enough for tornadoes but it was mostly speed shear. There wasn’t much turning with height. If you watch the radar, basically there were 3 different cells that came together right before west Knox and the outflow from the storm to the south provided a little more southerly flow at the surface to enhance shear. I’m not saying it was a one in a million but the situation was just timed perfectly for that tornado to spin up. I can understand why a warning wasn’t issued beforehand but I’m surprised it wasn’t issued after the CC drop showed up.


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[nrgjeff]

Thank you @PowellVolz so the CC dropped. Was rotation evident on radar? If not, I could see them thinking CC was something else. If a CC drop is co-located with rotation, then it should be a tornado warning. 

Back to today, I think the best shot is on the afternoon Mid-South mesoscale discussion. Boundary has slipped south of Memphis which is good. For chasers that flat Delta terrain is just what the doctor ordered! Though the meteorology remains conditional. 

[*Flash*]

4 minutes ago, nrgjeff said:

Thank you @PowellVolz so the CC dropped. Was rotation evident on radar? If not, I could see them thinking CC was something else. If a CC drop is co-located with rotation, then it should be a tornado warning. 

Back to today, I think the best shot is on the afternoon Mid-South mesoscale discussion. Boundary has slipped south of Memphis which is good. For chasers that flat Delta terrain is just what the doctor ordered! Though the meteorology remains conditional. 

For awareness...

[Holston_River_Rambler]

@nrgjeff

Here are the reflectivity and storm relative velocities from about 1250 PM through around 230:

 

 

 

[1234snow]

Where is this page? Link?


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https://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=17

[*Flash*]

Well, round 1 was pretty much non-existent. Even with ample moisture in play, it's hard to fathom enough energy making it north to metro areas to warrant the 'Enhanced Risk'. I've been wrong before though...

[Stovepipe]

3 hours ago, Holston_River_Rambler said:

@nrgjeff

Here are the reflectivity and storm relative velocities from about 1250 PM through around 230:

Damn dude, that's amazing that you saved those!  I had one crappy zoomed out screenshot that I saved from Radarscope that wasn't even post worthy.  You did a good thing there!   

[PowellVolz]

Thank you [mention=14393]PowellVolz[/mention] so the CC dropped. Was rotation evident on radar? If not, I could see them thinking CC was something else. If a CC drop is co-located with rotation, then it should be a tornado warning. 

Back to today, I think the best shot is on the afternoon Mid-South mesoscale discussion. Boundary has slipped south of Memphis which is good. For chasers that flat Delta terrain is just what the doctor ordered! Though the meteorology remains conditional. 

I’m by no means an expert but when I was watching Ref and Velocity, I didn’t see anything all that alarming until about 2:10pm on RadarScope. You could tell there was a little twist to the cluster on Ref. Inflow on Velocity wasn’t all that great but you could tell the backside had started to wraparound. The very next frame is when the CC drop showed up. The tornado was rainwrapped and I don’t have much experience with that but I have seen in the past that sometimes a rainwrapped tornado isn’t super clear on Velocity. Two frames later, or about 2:20 you could see the winds accelerate and bow out. Almost seemed like the RFD choked off the inflow and the cell collapsed creating the 70-80mph winds from Knoxville to Dandridge. In East Knoxville, RadarScope was reading 90-110mph at 2k feet.


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[Holston_River_Rambler]

9 hours ago, Stovepipe said:

Damn dude, that's amazing that you saved those!  I had one crappy zoomed out screenshot that I saved from Radarscope that wasn't even post worthy.  You did a good thing there!   

I didn't think about it at the time, but I have a radarscope account that lets me access historical data back to a point. 

[PowellVolz]

Damn dude, that's amazing that you saved those!  I had one crappy zoomed out screenshot that I saved from Radarscope that wasn't even post worthy.  You did a good thing there!   

Do you know how to look in the past on RadarScope?


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[Stovepipe]

1 hour ago, PowellVolz said:

Do you know how to look in the past on RadarScope?


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I did not know that was possible!

[1234snow]

I did not know that was possible!

You can click on the timestamp on the bottom right and it brings up a calendar where you go chose the date and time. Pretty cool.

[Stovepipe]

5 hours ago, 1234snow said:

You can click on the timestamp on the bottom right and it brings up a calendar where you go chose the date and time. Pretty cool.

Slick, thank you all for schooling me.  

[dwagner88]

23 hours ago, 1234snow said:

You can click on the timestamp on the bottom right and it brings up a calendar where you go chose the date and time. Pretty cool.

I must not be paying for this feature. I think I grandfathered into Pro Tier 1, not Tier 2 because I loathe subscriptions. I've had the app since 2015 I think.

EDIT: Nevermind. I don't even have tier 1. Apparently there are two subscription levels now.

[susqushawn]

Brief couplet

[*Flash*]

For awareness...

[Carvers Gap]

Was on the UTK campus when the deluge hit today.  I am not sure I have ever seen that much water running down Lake Avenue(lived up to its name!).  

[jaxjagman]

Some of the short range models has been showing the MCS crossing the river right now falling apart before it reaches middle and eastern Tn,they've been pretty bad as of late,so far it seems to be holding together,pwats are around 2" here so it could be a good soaker,thunderstorms in middle and east Tn in a few hours

[jaxjagman]

[jaxjagman]

 Mesoscale Discussion 1981
   NWS Storm Prediction Center Norman OK
   1153 AM CDT Sun Aug 13 2023

   Areas affected...Mid-Mississippi River Valley into the Tennessee
   Valley

   Concerning...Severe potential...Watch possible 

   Valid 131653Z - 131900Z

   Probability of Watch Issuance...40 percent

   SUMMARY...An MCS moving across the mid-Mississippi River Valley will
   likely see new re-intensification through the early afternoon hours.
   This will pose a threat for damaging to severe winds downstream.
   Trends will be monitored for possible watch issuance.

   DISCUSSION...A lingering MCS moving out of northern AR has gradually
   become outflow dominant per KNQA radar imagery over the past few
   hours. However, over the past 30-60 minutes new convective towers
   are noted in IR imagery and lightning data, developing along/just
   behind the gust front as it approaches the MS River. Further
   re-development and/or re-intensification of the line appears
   probable through the early afternoon as the MCS approaches a
   regional buoyancy maximum over northern MS to western TN (MLCAPE
   values between 2000-3000 J/kg and rising as temperatures warm into
   the low 90s). Deep-layer flow over the region is meager with the
   KNQA VWP and 12 UTC BNA sounding sampling mid-level winds between
   20-30 knots. This suggests that storm organization/longevity may be
   limited, but convectively-augmented (and poorly-sampled)
   mid/upper-level winds in the vicinity of the attendant MCV over
   northeast AR and the MO bootheel may support adequate deep-layer
   shear for a more organized/persistent severe threat. While
   confidence in favorable kinematics is somewhat low, a downstream
   damaging wind threat appears likely across western to middle TN and
   adjacent portions of KY, MS, and AL given the ample buoyancy. Trends
   will be monitored for possible watch issuance.

   ..Moore/Guyer.. 08/13/2023

[jaxjagman]

 URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 641
   NWS Storm Prediction Center Norman OK
   135 PM CDT Sun Aug 13 2023

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Northern Alabama
     Northeast Mississippi
     Middle Tennessee

   * Effective this Sunday afternoon and evening from 135 PM until
     800 PM CDT.

   * Primary threats include...
     Scattered damaging wind gusts to 60 mph possible

   SUMMARY...Storms are expected to continue to intensify across the
   region with a linear cluster evolving, with damaging winds as the
   primary severe hazard.

   The severe thunderstorm watch area is approximately along and 80
   statute miles north and south of a line from 60 miles northwest of
   Muscle Shoals AL to 60 miles southeast of Nashville TN. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU1).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

[dwagner88]

Utterly spectacular lightning show tonight. Best one in years around here.

[nrgjeff]

Sexy outflow boundary sits to my west, even with a kink. Too bad it's capped and directional shear is low. Only speed shear is there.

For that 2% Upper Plateau.. gonna need that outflow boundary to lift north. Possible with a break in the action, but I'm an Under bet.

[PowellVolz]

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[John1122]

Curious as to whether there's enough juice left here to re-fire storms or not. Two rounds today has kept temperatures in the 70s. Cloudy now with an occasional peek of sun.