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jaxjagman

Tn Valley Severe Weather

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And of course the one we've been watching for: The trough/phase dynamics at play, leading to a potential outbreak on Easter Sunday. This might be a doozy:

 

 

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8 hours ago, Windspeed said:

And of course the one we've been watching for: The trough/phase dynamics at play, leading to a potential outbreak on Easter Sunday. This might be a doozy:

 

 

 

Big shift to the west overnight

760838bb-67de-4ea8-9f8c-88c0a420de47.gif

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This morning’s short term AFD from MRX:

Moving into/through Wednesday, conditions across the TN Valley will
improve as the day progresses with the aforementioned low clouds
scting out to favor low cu and ample heating amongst sustained
sly/swly moisture advection.  With that, did keep pops mentionable
albeit low during peak heating as iso/sct convection is possible
once convective temps are reached (highs in the 70s to low 80s),
with low confidence in placement. Meanwhile the synoptic pattern
really starts to amplify as a fast moving H5 wave/trough dives out
of Canada across the Northern Rockies into the Plains, resulting in
surface cyclogenesis across MO/IL.  This deepening surface low will
propel a fast moving cold front into a very moist/unstable warm
sector over the OH Valley late Monday evening with ample convection
to accompany. This frontal convection will then race across the
Plateau, through the Great Valley, and into the Southern
Appalachians around sunrise Thursday.

Profiles in the warm sector across East TN are fairly impressive
ahead of the convection (despite the timing) with very steep lapse
rates amidst deep dry air and unidirectional/strong sheer. As for
hazards, nothing is off the table as large hail and damaging winds
are certainly the primary threats, but an isolated tornado or two
cannot be ruled out as some embedded rotations are likely.
Instability does look to wain closer to daybreak as the line of
convection moves east, mainly just on diurnal trends, therefore
would expect some gradual weakening closer to the NC line.  All
said, SPC has upgraded areas generally west of I75 to an Enhanced
Risk of severe thunderstorms, which is where instability/shear are
maximized, while the remainder of the area is essentially favored in
the Slight Risk Category.  As for timing specifics, the CAMs seem to
be in fairly good agreement with only one slower outlier.  Typically
these fronts outperform as far as speed/timing thus leaned away from
the slower outlier thereby favoring a fast fropa between midnight
and 5-6AM eastern time.
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This Easter Sunday outbreak looks like it could be ugly to me on the Euro.  I don't know very much about severe parameters or exactly how ugly, but as Webb's cyclone map that Windspeed posted says, one look at that is all I need. I am not a fan of storms moving SW -> NE with a strong upper low moving over the bootheel of Missouri, since that can send them right up the river valleys in East TN with a lot of shear. Most damaging storms I can remember have that motion. 

Looking at Pivotal soundings, still looks like most of the worst is S and SE of east TN, but all I'm going on is the "threat box" if that is what it is called, where it tells you the possible wx threats. Most soundings over middle E TN give a "Marginal Severe" result, with "Marginal Tornado" nearer Nashville, but near Chatt it is giving a tornado result, with storms moving up the TN river valley near the mts.  Euro suggests that there could be a bigger line/ clusters of cells moving through first, and then more with a secondary line of discrete cells as the front moves through.  

What do y'all who know a lot more about severe weather think? 

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By the Grace of God, my family and friends survived the last few tornadoes that came through McMinn County, including the monster back in 2010 (or 2011; whichever was first, because there were two consecutive years of tornadoes hitting us).  I do not like when the term "outbreak" starts getting thrown around, as I'm sure many others do not.  :blink:

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This Easter Sunday outbreak looks like it could be ugly to me on the Euro.  I don't know very much about severe parameters or exactly how ugly, but as Webb's cyclone map that Windspeed posted says, one look at that is all I need. I am not a fan of storms moving SW -> NE with a strong upper low moving over the bootheel of Missouri, since that can send them right up the river valleys in East TN with a lot of shear. Most damaging storms I can remember have that motion. 
Looking at Pivotal soundings, still looks like most of the worst is S and SE of east TN, but all I'm going on is the "threat box" if that is what it is called, where it tells you the possible wx threats. Most soundings over middle E TN give a "Marginal Severe" result, with "Marginal Tornado" nearer Nashville, but near Chatt it is giving a tornado result, with storms moving up the TN river valley near the mts.  Euro suggests that there could be a bigger line/ clusters of cells moving through first, and then more with a secondary line of discrete cells as the front moves through.  
What do y'all who know a lot more about severe weather think? 

The overall synoptic pattern is incredible, but what will make or break is going to be in the short term, such as WF position, junk convection, etc.

27/4/2011 was really tampered back for Middle TN because of consistent rain and convection to the south keeping things much more stable.


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The good the bad and the ugly.

Bad first: Tonight looks like an overnight event.

The Good: I don't see enough turning (low or upper level) for a big tornado risk. Wind and hail yes, especially from sups. Instability could cause some gorilla hail Midsouth. Yeah we'll have some sups, but turning wind is not that bad. Helicity forecasts are up due to speed shear, but directional is meh.

The Ugly: Forecasting an Outbreak Day 5 Sunday. Who knows? Maybe a Gulf Coast MCS will rescue all of us. I mean, it is Easter!

Since we can't chase right now, might as well side with the Public and wish against severe.

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Thanks Jeff and Calderon for the replies. McMinn, sorry about the outbreak word, I was probably too loose with that as far off as things are now. It is 2020 after all though, so my mind just went to worst case right away, lol. 

Yeah, hopefully something kills this threat Sunday AM, no one needs power outages and other major infrastructure problems right now. 

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24 minutes ago, Holston_River_Rambler said:

Thanks Jeff and Calderon for the replies. McMinn, sorry about the outbreak word, I was probably too loose with that as far off as things are now. It is 2020 after all though, so my mind just went to worst case right away, lol. 

Yeah, hopefully something kills this threat Sunday AM, no one needs power outages and other major infrastructure problems right now. 

Oh, wasn't directing that at you or anyone else!  :D No need to say sorry!  I have a little PTSD from that time.  :weep:

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The good the bad and the ugly.
Bad first: Tonight looks like an overnight event.
The Good: I don't see enough turning (low or upper level) for a big tornado risk. Wind and hail yes, especially from sups. Instability could cause some gorilla hail Midsouth. Yeah we'll have some sups, but turning wind is not that bad. Helicity forecasts are up due to speed shear, but directional is meh.
The Ugly: Forecasting an Outbreak Day 5 Sunday. Who knows? Maybe a Gulf Coast MCS will rescue all of us. I mean, it is Easter!
Since we can't chase right now, might as well side with the Public and wish against severe.


Jeff... how much influence could the cluster moving out of Ohio into Virginia effect our area? I’m worried it could lay down a secondary boundary somewhere across ETn and possibly enhance the storms by adding more shear, or even causing the surface winds to back a little. Thoughts?


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Quick discussion about a possible secondary boundary setting up SW of the current MCS complex (currently moving through EKY->SWVA->TriCities) over portions of ETN Valley later tonight when the main event rolls through. Could that add to the dynamics in play for some brief QLCS spinups?

 

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Quick discussion about a possible secondary boundary setting up SW of the current MCS complex (currently moving through EKY->SWVA->TriCities) over portions of ETN Valley later tonight when the main event rolls through. Could that add to the dynamics in play for some brief QLCS spinups?

 

I think this is possible. Kinda depends on where the boundary gets laid down at.


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9 minutes ago, Runman292 said:

In the latest update from the SPC, the 5% Tornado probability has expanded into the Eastern Valley.

Can you link?

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I think the HRRR missed the boat,talk about bad ,can't say much for the other models either.Models are not doing a very good job lately

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1 hour ago, Holston_River_Rambler said:

Yeah same here. Lucked out with some heavy rain to knock the pollen down though. 

I agree with the pollen,its been brutal

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Wednesday night southwest flow apparently washed out any boundary. The veered off onslaught saved us from spinners.

19 hours ago, PowellVolz said:

Jeff... how much influence could the cluster moving out of Ohio into Virginia effect our area? I’m worried it could lay down a secondary boundary somewhere across ETn and possibly enhance the storms by adding more shear, or even causing the surface winds to back a little. Thoughts?

Then the 5% East Tenn. Wow it was obvious back around midday Wednesday that's not necessary. 

11 hours ago, jaxjagman said:

I think the HRRR missed the boat,talk about bad ,can't say much for the other models either.Models are not doing a very good job lately

Might explain SPC. With all due respect, they've been way too model dependent the last couple seasons. Especially the amped up HRRR.

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MJO is now headed into some favorable phases,when it gets into the eastern IO seems some uncertainty afterwards,CFS  seems to want to show the GWO going -ve but still into the COD,but even so the East Asia seems like its going to get active once again.Depending on the teleconnections their could be a system in the long range as  as a trough went through the Yellow Sea into S/Korea yesterday,possibly the end of next weekend we might see something.As well you should look at the ENSO,after the MJO, Kelvin and a WWB on going, region 4  might not be the hot spot but east of the IDL might be,and  could excite once again the S/Jet even more down the road

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