Tn Valley Severe Weather

[PowellVolz]

Is Thursday worth watching?


.

[jaxjagman]

Pretty active start of 2023 in Jan

 

https://en.wikipedia.org/wiki/List_of_United_States_tornadoes_in_January_2023

[Matthew70]

With the way the temps are showing next week & after. I would say February could be active south of TN. 

[PowellVolz]

Pretty active start of 2023 in Jan
 
https://en.wikipedia.org/wiki/List_of_United_States_tornadoes_in_January_2023

How does our pattern translate to severe this spring?


.

[jaxjagman]

On 1/29/2023 at 4:56 PM, PowellVolz said:

How does our pattern translate to severe this spring?


.

I'm not really sure,the MJO signal looks to really weaken as we get around MId Feb,both the Euro and CFS are showing this,GEFS right now keeps a stronger signal into the WP out of the COD.

 

Seems like at least we;ve seen this same pattern out west since Nov,wash,rinse and repeat.The MJO signal gets strong then it goes into suppression after, then strong then suppressed again and so on.So seemingly if the patten recycles like it has we'll start seeing a stronger signal into Africa and the IO into March,but thats JMO and certainly might be wrong

[nrgjeff]

Severe wx enthusiasts need the next SSW to fail as miserably as the last. A SSW follow through would crush the early season. Not in time for winter snow, just in time to make spring blow (chunks not severe).

[jaxjagman]

Not looking good for failure,not right now anyways

[Matthew70]

2 hours ago, jaxjagman said:

Not looking good for failure,not right now anyways

Cold spring incoming 

[Matthew70]

Looking at temps. forecast.   We are already in a March type pattern.  Cold 1-2 days then back up to near spring temps. 

[jaxjagman]

This SEEMS to be headed towards 2018 when there were no EF4-5'S that year.Japan had the BAIU FRONT  establish in which caused catastrophic flooding in that region.Flooding in India.Couple strong phoons .There was a couple strong hurricanes,Florence for one.We also had a fall tornado outbreak in Nov.,just a few events noted.

 

Based on the ONI it does look certainly possible when we get into spring it could become more neutral.We just as well had a similar SSWE into Feb(pic below)

 

Who knows,but by my observation as of right it seems to be headed towards a more 2018,this does not mean anything historical will happen again  that was noted above.

[nrgjeff]

Wednesday looks Mid South and into our Region late; but, I focus on Thursday which should be daytime and my neck of the woods.

Wednesday plays a role with the lead wave to start moisture return. Not often we get a primer day this early in the season. Thursday should be ready to go!

Wind fields most of the way up strengthen and turn with height. LLJ could get funky with wave timing but it's too early for that type of stuff or hodos. Said LLJ could be more unfettered south, with a southern upper wave...

Which brings me to surface pattern recognition. Should be a Gulf front in the Deep South (well south of WF) intersecting with a pre-frontal trough (esp if southern wave). 

While the ingredients are there, SPC is right to hold 15%* instead of 30 percent. Other (more bearish) scenarios include rain-out or upper wave timing subsidence during the day Thursday.

*Sunday 4-8 day

[jaxjagman]

Probably better to wait until  around next weekend,But the GFS and Euro seems to be hinting at some potential strong storms in its long range

[jaxjagman]

But who knows down the road.The Euro seems like it wants to to build back the Mid level ridge again down into Cuba/Bahamas,and a Upper Level Ridge around the Mid Atlantic.Seems like the same pattern we are seeing mid week once again

[nrgjeff]

Little change to thinking for Thursday. Trough is going in a positive tilt direction. However plenty of turning with height is evident, and it is quite enough for the South or Ohio Valley.

Key will be if this verifies, or something like it. Perturbation is shown on the low-level trough, which enhances low level flow in North Alabama. Forecast 925 mb winds are shown; however, the 850 mb chart (not shown) doesn't echo it (adds uncertainty).

Also not shown - but on the bullish side - 700/500 mb vort max and new southern stream 250 mb jet (south of the main OV jet stream). 

Day 4 is still too early to dig into such mesoscale details. However it is what one would look for, if seeking a 30% from SPC.

Broad pattern wind fields and thermodynamics are there. Still a southern stream wave is required in the positive tilt environment.

Also yet to show up is an obvious pre-frontal trough and Gulf front intersection, though some NWP has hints. That's a Day 2 deal really.

Other options include tomorrow (Day 3) NWP going rain-out or poor wave timing. Just 15% is prudent for Day 4 today.

[jaxjagman]

 NWS Storm Prediction Center Norman OK
   1147 PM CST Tue Feb 14 2023

   Valid 151200Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE LOWER MISSISSIPPI VALLEY AND WESTERN TENNESSEE VALLEY...

   ...SUMMARY...
   Widely scattered severe thunderstorms are possible over parts of
   Texas and Oklahoma beginning late in the day and into the evening on
   Wednesday. A severe threat will also develop overnight over the
   lower Mississippi Valley/Mid-South region, with a tornado risk.

   ...Eastern OK/North-Central TX to the Mid-South...

   Late-evening satellite imagery depicts a well-defined upper low
   digging southeast into northern AZ. This feature is forecast to
   shift into the southern Rockies by mid day as a 110kt 500mb jet
   translates across the desert southwest toward the southern High
   Plains. With time this feature will advance into eastern KS allowing
   the trough to become more positive tilted as it moves into the
   central Plains. This evolution will maintain broad southwesterly
   flow across lower latitudes, including the Mid-South region. Of
   particular concern will be the development of a pronounced LLJ
   across the lower MS/TN Valley, especially during the latter half of
   the period when a marked increase is expected (in excess of 60kt).
   More appreciable mid-level height falls will remain north of the
   higher-buoyancy air mass, thus low-level warm advection will likely
   prove instrumental in the majority of supercell development through
   the period.

   At 05z, a narrow band of strongly-forced convection is observed
   along the front over AZ. Otherwise, most of the southern states are
   convective free with strong capping. Low-level trajectories favor
   Gulf air mass advancing inland across the lower MS Valley, and mid
   60s surface dew points are well established at this time over much
   of the upper TX Coast and LA. Latest guidance suggests this air mass
   will easily advance north into AR/western TN Valley later today;
   however, convective development will likely remain suppressed until
   the latter half of the period when the LLJ intensifies in response
   to the approaching short wave.

   Upstream, strong boundary-layer heating across the southern High
   Plains will result in very steep surface-3km lapse rates from the
   southern TX Panhandle into western OK/northwest TX. It appears this
   steep lapse rate plume will overspread the northwestern portions of
   return moisture across south-central OK/north-central TX, just ahead
   of the front/dry line. As temperatures warm into the lower 70s
   capping should weaken and scattered convection is expected to
   develop. Forecast soundings favor supercell development and this
   activity should spread east during the evening hours with an
   attendant threat for all hazards.

   Downstream, LLJ will increase across LA into western TN from late
   afternoon into the evening. Steep mid-level lapse rates will
   overspread this region as 3km capping gradually weakens. As the cap
   weakens, isolated discrete supercells are expected to evolve within
   a moistening, warm advection regime. ESRH values in excess of 300
   m2/s2, along with steep lapse rates, and modest instability favor
   severe supercells capable of producing tornadoes, possibly strong. A
   corridor of supercells may ultimately evolve along an axis from
   southeast AR into western TN, during the latter half of the period,
   as the cold front will not advance east of the MS River prior to
   sunrise. Warm advection should be the primary forcing mechanism for
   this activity, thus episodic bouts of severe are possible.

   ..Darrow/Thornton.. 02/15/2023

[Runman292]

Maybe it is just me, but it does seem like most setups for severe weather in East TN is either High shear/Low CAPE or vice versa. Is the terrain the primary reason why East TN rarely gets both parameters strong at the same time?

[PowellVolz]

Maybe it is just me, but it does seem like most setups for severe weather in East TN is either High shear/Low CAPE or vice versa. Is the terrain the primary reason why East TN rarely gets both parameters strong at the same time?

I’m not going to pretend I know half as much about severe weather as @jaxjagman but here’s my opinion based on what I have seen over the years and I’d like for Jax to chime in.

ETn IMO is very specific to low level wind direction and storm mode. The majority of our severe weather events are linear or QLCS because of troughs becoming more positive tilt as the move east. Most of our surface winds in severe weather comes from the SW which means our low level winds are running almost parallel to storm motion. So we end up with very little to any low level turning. So for ETn to get more low level rotation we need more South to SE surface winds. So that creates the issue of the surface winds having to go up and over the mountains. Obviously that creates more problems. So how do we get more turning at low levels? Have a more west to east storm track. This gives ETn more turning angle in the lower levels. Out of all the tornadoes that have touched down in or around Knoxville since I’ve been around have a more west to east storm track. The only exception would be in and around the foothills where the mountains create it’s own micro climate of the winds backing a little more. 3 notable tornado touch downs around Knoxville stand out. February of 93’ a EF3 tornado tracked from Oak Ridge to Powell to Hallls in a west to east motion. In April of 98, a EF2 tornado tracked west to east from Claxton to Powell to Ft City. In November 2002 a strong EF3 tornado tracked just north of Knoxville from Cumberland Co to southern Morgan Co to Anderson Co. Now that storm wasn’t as W to E as the other ones as it had a slight movement of S to N in it. There’s been a couple of tornadoes in Claiborne Co around Tazewell and those were more west to east based. Now I’m not at all saying ETn can not get a tornado to touch down with a SW to NE track because we had a weak one just a month ago in Jefferson Co but IMO I feel like more west to east based cells have more potential than SW to NE tracks.


.

[jaxjagman]

4 hours ago, Runman292 said:

Maybe it is just me, but it does seem like most setups for severe weather in East TN is either High shear/Low CAPE or vice versa. Is the terrain the primary reason why East TN rarely gets both parameters strong at the same time?

Not even sure what might happen here.Still look like early rains and clouds might hold back any severe.Like SPC mentions.I think for you guys its more timing,GFS/NAM seem to be showing loss of diurnal heating the severe threat falls off markadly,dont mean you still cant get severe storms

[nrgjeff]

Thanks @PowellVolz I couldn't have said it better. Gonna award the above, Post of the Month. Could be Post of the Year, but I have only skimmed winter stuff. Severe is easier to follow since it's a niche topic.

OK for tonight, Wednesday, unlucky timing for the Mid South is overnight. Looks like lots of blobs, but some of those will be genuine supercells. Not ideal overnight. Flooding will be a problem too, esp where multiple cells train.

Thursday is my day of interest. Trough is positively tilted, which also veers Tennesse low level winds, and should keep Tennessee mainly straight line winds. Could be strong and plenty of it though.

Alabama is a little more interesting with higher temps/dews and instability. Showers today (Wednesday) ensure the pattern recognition Deep South (DS) boundary lifts north Thursday. South if it low level winds may be more straight south and stronger.

DS boundary intersection with front should be an area of interest. Some CAMs already have a right mover in that spot. Day ahead one should not trust that location, or even the outcome. However it means CAMs "see" a boundary intersection. Will it happen?

Technically that's south of our Region. We'll leave the Spann jacket, tie, button and suspenders forecast to the Southeast region.

[jaxjagman]

ay 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1128 AM CST Wed Feb 15 2023

   Valid 161200Z - 171200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   MISSISSIPPI AND ALABAMA NORTHWARD INTO SOUTHWEST OHIO...

   ...SUMMARY...
   Widely scattered severe thunderstorms are likely from the central
   Gulf Coast states northward into the Ohio Valley on Thursday.
   Several tornadoes are possible over Mississippi and Alabama,
   including the risk for isolated strong tornadoes.

   ...Synopsis...
   An elongated positive-tilt upper trough will extend from the upper
   Great Lakes into the southern Plains by 00Z, with a primary/leading
   midlevel jet over 110 kt from MO into Lower MI and a dry slot
   developing from St. Louis to Lake Erie. After 00Z, a secondary wave
   will move from the southern Plains toward the lower MS Valley, with
   increasing height falls and strengthening winds aloft across the
   southeastern states.

   At the surface, low pressure will move from southern IL into OH by
   00Z, reaching New England by Friday morning. A cold front will
   extend south from the low, crossing the MS River by late morning,
   and proceeding into the mid OH/TN Valleys by late afternoon.
   Meanwhile, a warm front will extend east from the low Thursday
   morning, across central IN and OH. Southerly winds across the warm
   sector will maintain a plume of 60s F dewpoints as far north as the
   surface low, with mid 60s F across the lower MS Valley. More
   substantial moisture will be in place over LA, with upper 60s F
   translating eastward across southern MS/AL and the FL Panhandle by
   Friday morning with the cold front roughly from western PA to FL by
   this time.

   A broad area of 40-50 kt southwesterly flow at 850 mb will exist
   atop the entire warm sector, enhancing low-level shear. The
   combination of a moist air mass and favorable shear over a large
   area will likely support corridors of severe storms, including a few
   tornadoes through the period.

   ...LA...MS...AL...
   A cold front will move into western MS and south-central LA by
   midday, where ample moisture will be in place. Storms both along and
   ahead of the front will be possible as the air mass will be
   uncapped, with upper 60s F dewpoints likely sufficient to support
   surface-based parcels. Effective SRH around 300 m2/s2 will be common
   along the eastern edge of the instability plume, and supercells will
   be possible with tornado risk.

   As height falls and winds aloft increase overnight, the cold front
   will continue to support strong to severe storms, with 50 kt flow at
   850 mb and mid to upper 60s F dewpoints from southern AL into the FL
   Panhandle. Hodographs will be quite favorable for tornadic
   supercells, with the primary mitigating factor being cool/marginal
   boundary-layer temperatures.

   ...OH Valley into TN...
   Storms are likely to be ongoing across much of TN and KY, perhaps
   extending into northern MS and along the AR/MS border, within a warm
   advection regime beneath 50-60 kt 850 mb flow. The instability axis
   will be near the MS River Thursday morning, thus storms across
   western areas may have tornado or damaging wind potential at that
   time. Much will depend on existing storm modes at the beginning of
   the day, as heating will be limited, and outflow may both provide a
   focus for new development or stabilize portions of the warm sector.

   During the afternoon, areas of air mass recovery may occur ahead of
   the cold front and behind the early day storms. In addition, some of
   the existing storm complexes could evolve/reorganize across KY and
   TN. Shear profiles will strongly favor supercells with tornado
   threat, but little heating and ongoing precipitation may limit
   surface temperatures.

   Farther north, a dry slot should clear out much of the area around
   IL and northern IN, but southern IN into OH will remain sufficiently
   unstable for severe storms given strong shear. The area along and
   east of the surface low track may favor isolated supercells,
   assuming the surface air mass can warm into the mid 60s F.

   ..Jewell.. 02/15/2023

[nrgjeff]

Oh my! Day 2 the 10% hatched creeps up close to that flatter terrain of northwest Alabama. Could happen. I still like more cental Alabama in my post a few minutes ago above. We shall see. 

I will add that Jax is right about East Tennessee this week. Powell covers the general issues / climo (worth a read above) and Jax has the Thursday specific weather.

[jaxjagman]

We just live in a weird environment seemingly.The mountains wreck havocs on snow or severe

[PowellVolz]

I don’t know if I’ve ever seen a trough go this positive tilt before which has caused it to become a strung out mess for tomorrow. I do believe central Ala up to southern central Tennessee has the best chance of tornadoes but forcing is weak and unless we get a short wave, WAA is the main driver. Cams are suggesting the bulk of the morning convection will stay north of ETn. 850’s are screaming up the valley when the afternoon line moves in. I think flooding is the biggest issue for Tennessee east of Nashville.


.

[Matthew70]

Couple of Tor warnings in west TN early this morning.  Is it me or is the Memphis radar down?  If it is that’s really bad timing. Mid 60s dews all the way up to Missouri border this morning.  Could be a busy day.  Hopefully not.

[Holston_River_Rambler]

15 hours ago, PowellVolz said:

I don’t know if I’ve ever seen a trough go this positive tilt before which has caused it to become a strung out mess for tomorrow.

I swear on the OP models it almost looks like the "wave riding the front" scenario, but it's just so warm we don't get any snow with said wave. Sort of presents like an extra uumph of precip coming out of the Gulf between 0 and 12z overnight. 

What I'm looking at is the front looks like it is through NW MS at the start of that gif, but then the precip starts to build back and hammers the plateau eastward with heavy precip after midnight. 

But hey, at least there might be a flurry or two tomorrow above 2500' lol. 

I'll go back and hide now in my "winter without winter weather" thread. 

[PowellVolz]

SPC added middle Tennessee to the 10% hatched tornado and it sounds like a upgrade is coming for MTn to a moderate risk.

“Kinematically, a period of strengthening shear is expected into the
afternoon, followed by leveling off and perhaps some lessening of
shear due to veering surface winds. This will lead to varying but
generally large hodograph sizes and shapes, but with effective SRH
generally remaining in the 250-400 J/kg range over much of the area.
The wind profiles throughout that cycle will be favorable for
supercells, with effective-shear magnitudes in the 45-55-kt range
over southern areas, to 50-60 kt across the Tennessee Valley region.
A northward extension of significant-tornado probabilities is being
made accordingly, and some parts of this region may need a further,
tactically focused, tornado-driven upgrade today, as mesoscale
trends and later objective guidance warrant”


.

[jaxjagman]

3 minutes ago, PowellVolz said:

SPC added middle Tennessee to the 10% hatched tornado and it sounds like a upgrade is coming for MTn to a moderate risk.

“Kinematically, a period of strengthening shear is expected into the
afternoon, followed by leveling off and perhaps some lessening of
shear due to veering surface winds. This will lead to varying but
generally large hodograph sizes and shapes, but with effective SRH
generally remaining in the 250-400 J/kg range over much of the area.
The wind profiles throughout that cycle will be favorable for
supercells, with effective-shear magnitudes in the 45-55-kt range
over southern areas, to 50-60 kt across the Tennessee Valley region.
A northward extension of significant-tornado probabilities is being
made accordingly, and some parts of this region may need a further,
tactically focused, tornado-driven upgrade today, as mesoscale
trends and later objective guidance warrant”


.

Quite a convective system overnight here,looking like some of the rains the models were showing came in a few hrs faster

[jaxjagman]

https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=mesoscale_01&x=1549&y=645&z=2&angle=0&im=60&ts=1&st=0&et=0&speed=130&motion=loop&maps[borders]=white&lat=0&p[0]=cira_glm_l2_group_energy&opacity[0]=1&pause=0&slider=-1&hide_controls=0&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&draw_color=FFD700&draw_width=6

 

Moved North of us now but it woke me up a few times..lol

[jaxjagman]

ational Weather Service Nashville TN
639 AM CST Thu Feb 16 2023

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE FOR SEVERE STORM POTENTIAL...
Issued at 628 AM CST Thu Feb 16 2023

The 12Z sounding from OHX shows a moist, highly-sheared, and
potentially unstable atmosphere already in place. Fortunately,
the radiosonde release took place before the current storm moved
over the office, so the profile is uncontaminated. The current
surface-based CAPE is 0 and the LI is also 0. However, the
forecast surface-based CAPE is 879 J/kg with a corresponding LI of
minus-4. The mid-level lapse rate is 7.2 C/km, so this suggests
the potential for strong updrafts especially with the help of the
cold frontal boundary this afternoon. The observed 0-3 SRH is a
robust 530, which is about what we expected with this environment.
The wind is 48 kts at 900 meters AGL, so there is a considerable
amount of low-level wind shear already present. Finally, the
precipitable water value is 1.41 inches, which is a record high
PWAT value for this date/time. The mid-level dry layer which was
showing up on previous soundings, including just 6 hours ago, has
completely disappeared.

&&

.SHORT TERM...
(Today through Friday)
Issued at 218 AM CST Thu Feb 16 2023

This is turning out to be a very interesting forecast for
February! I might have even forgotten for a bit that it is barely
mid February. We had a few strong storms overnight with the warm
sector but this has transitioned to a heavy rainfall threat at the
moment. 06Z sounding had a surface cape of 62 J/KG but a PW of
1.20 inches. Cancelled Watch #34 for our CWA as convection seems
to be elevated and HRRR shows the CAPE really dropping off through
10Z. Fully expect additional watches later this morning and
afternoon with the very strong cold front.

Severe parameters from the 06Z HRRR is very impressive today
especially this afternoon and early evening. It has very high
shear and helicity through the day. MUCAPE picks up near the
Tennessee River by 15/16Z to 1100+ J/KG and spreading to Nashville
Metro by 18/20Z of 1200+ J/KG and then dropping to 500-700 J/KG
by 23Z. Timing is very challenging as it seems like the potential
for severe weather will be through the day. It might be easier to
say when it will end and that will be with the cold front. Making
an educated guess...the best timing is just out a head and with
the front...or from noon west to 6 pm east. Please stay weather
aware as all severe weather types of straight line
winds...hail...and tornadoes will be possible. The HRRR supercell
composite and Significant Tornado Parameter really highlights
several areas across middle TN from 18-00Z. Please stay weather
aware and please encourage your social network to do the same.

Once the cold front passes it will be on the cold side tomorrow
with highs in the upper 30s to middle 40s.

[Matthew70]

4 hours ago, jaxjagman said:

https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=mesoscale_01&x=1549&y=645&z=2&angle=0&im=60&ts=1&st=0&et=0&speed=130&motion=loop&maps[borders]=white&lat=0&p[0]=cira_glm_l2_group_energy&opacity[0]=1&pause=0&slider=-1&hide_controls=0&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&draw_color=FFD700&draw_width=6

 

Moved North of us now but it woke me up a few times..lol

Woke me up also.  Quiet the show as is was the opposite of quiet.