Tn Valley Severe Weather

[jaxjagman]

17 Mar 2018	1012.51	1000.90	35.90	6.47	1.33
18 Mar 2018	1013.04	1006.25	12.83	7.15	1.58
19 Mar 2018	1012.24	1009.65	-7.28	7.35	1.57
20 Mar 2018	1010.11	1007.75	-8.38	7.51	1.49
21 Mar 2018	1008.59	1005.75	-6.08	7.82	1.45
22 Mar 2018	1010.01	1004.20	8.14	8.52	1.65
23 Mar 2018	1012.84	1003.70	24.08	9.45	2.06
24 Mar 2018	1014.29	1005.35	23.12	9.73	2.42
25 Mar 2018	1014.02	1007.00	13.93	9.42

 

 

The big drop in the SOI into Mid March would show volatility around the time frame mentioned above

[CheeselandSkies]

15 hours ago, jaxjagman said:

Asia shows a trough going through Mongolia by day 7 on the Euro then a upper low into China,the typhoon is still being shown to die out.Either way towards the end of week one into week 2 of April we could be once again looking at a good system.The whole chorus this late winter into early spring has been suppressed systems.But still i see some good signals.On the RRWT lifted Index it's showing the lift tapping into the GOM and coming into the lower OV,with the BSR maps showing a warm front lifting northward into the lower OV with a cold front on it's heels.

LOL, I like the "storm" and "developing gale" notations across the central CONUS.

[nrgjeff]

Operational models are beginning to show more surface low press in the 11-15 day which lines up with the discussion above. GFS is more consistent than a day ago, sending stout low press through the Ohio Valley. Euro ensembles surface low spaghetti plots are mighty active too.

Early season one often looks for the warm front. Most readers know I also favor outflow boundaries OFB. Going into April the classic severe signature is actually low press to the north, with a trailing surface trough through the South. Said trough should also show a bow shape through the southern states. Shape is from a surging cold front or pre-frontal trough. For chasing I still like OFB intersections, but down the trough is as active or moreso than the warm front in a textbook April setup.

Like with snow, the 11-15 day is fantasyland. Those with severe wx concerns need not be worried. Enthusiasts keep looking for that surface pattern, plus strong upper level winds turning with height. West Pacific tropical storm adds uncertainty to the 11-15 day.

UPDATE: Last 24 hours of NWP have trended cooler in the 11-15 day. Could zig zag some more before settling. West Pac TS keeps churning. US Navy and Japan Met Agency both have it gradually strengthening to 50 kts before slowly winding down. Turns north away from the Phils and into open sea. Back home, cooler 11-15 is lower risk severe.

THIS WEEK 3/28-29: Diurnal timing looks off for severe. Wave and surface low try to strengthen Wednesday, but over the Ozarks southward. Cool pool also stabilizes. System passes through Thursday morning and weakens during the day. So, just heavy rain here. Deep South is closest severe threat. If interesting I'd post Southeast sub/region.

[rolltide_130]

Going to need to watch these next couple of weeks closely.. some alarming analogs are popping up and the trend is towards a massive, low-amplitude trough to sweep through here within the D 10-15 range. Those can spell trouble.. 

[jaxjagman]

Chance for some severe storms Tuesday into Tuesday evening by both the GFS and Euro.But as to what extent is yet to be determined.The key player for what i see is how the models this afternoon handle a shortwave trough.The GFS is showing the feature suppressed into Dixie Alley while the Euro is showing this trough into the TN Valley.This would have more ramifications with severe for us in the Valley "IF" the Euro is right.

[jaxjagman]

Also some good analogs showing up,for Tuesday

[jaxjagman]

Looking down the road, Asia is fixing to get cranking in the long range  by day 6-7 day period.The MJO is being shown into the IO the 2nd week of March,the AAM is crashing almost -3 sigma.Papers documented with the the MJO getting into the IO and the AAM gets into lower phase 2 shows large tornadoes would be possible during this period in a Nina year.It don't mean for the Valley,just worth mentioning

[jaxjagman]

The Euro looks more the GFS tonight,either way some parts of the Valley would see some strong storms possibly Tuesday

[CheeselandSkies]

On 3/31/2018 at 6:36 PM, jaxjagman said:

Looking down the road, Asia is fixing to get cranking in the long range  by day 6-7 day period.The MJO is being shown into the IO the 2nd week of March,the AAM is crashing almost -3 sigma.Papers documented with the the MJO getting into the IO and the AAM gets into lower phase 2 shows large tornadoes would be possible during this period in a Nina year.It don't mean for the Valley,just worth mentioning

It would be helpful for non-mets if posts like this with multiple teleconnection acronyms could include a quick summation of what that means for sensible weather in this sub and the rest of the CONUS. This one does (increased severe potential), but I find that's not always the case.

I know what MJO stands for, but haven't the foggiest about what it means for it to be into the IO or what the AAM crashing almost -3 sigma means.

[jaxjagman]

7 hours ago, CheeselandSkies said:

It would be helpful for non-mets if posts like this with multiple teleconnection acronyms could include a quick summation of what that means for sensible weather in this sub and the rest of the CONUS. This one does (increased severe potential), but I find that's not always the case.

I know what MJO stands for, but haven't the foggiest about what it means for it to be into the IO or what the AAM crashing almost -3 sigma means.

Here's a abstract for the MJO,i've been out of town and just got back or i'd have replied back sooner.

 

Abstract

The Madden–Julian oscillation (MJO) has been linked to weather variability in the midlatitudes via its associated overturning circulations and Rossby wave trains that redistribute the thermal and mass fields at higher latitudes. This work examines the relationship between the MJO and violent tornado outbreaks in the United States. A census of events shows that violent tornado outbreaks during March–April–May (MAM) are more than twice as frequent during phase 2 of the Real-time Multivariate MJO (RMM) index as during other phases or when the MJO was deemed inactive. Composite analyses show the global circulation patterns simultaneously associated with the MJO and the tornado outbreaks and also indicate the most favored low-frequency circulation pattern that precedes tornado outbreaks in RMM phase 2. An index of 300-hPa geopotential height data is generated by projecting 60-day mean values onto the composite low-frequency pattern. When that index exceeds one standard deviation and the MJO is in RMM phase 2 with an amplitude exceeding one standard deviation during MAM, violent tornado outbreaks occur 50% of the time, relative to the average frequency of less than 4%. Results demonstrate that the anomalous large-scale midlatitude circulation modulated by the MJO and lower-frequency signals can make conditions more or less favorable for tornado outbreaks.

https://journals.ametsoc.org/doi/abs/10.1175/MWR-D-12-00173.1

 

Here's a paper on the GWO

 

https://www.researchgate.net/publication/284217379_Tornado_frequency_in_the_United_States_related_to_global_relative_angular_momentum

 

[jaxjagman]

 Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   1257 AM CDT Tue Apr 03 2018

   Valid 031200Z - 041200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHWEST
   OHIO...CENTRAL AND SOUTHERN INDIANA...AND SOUTHEAST ILLINOIS
   SOUTHWEST TO EASTERN ARKANSAS AND NORTHERN MISSISSIPPI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENH RISK AREA...AND EXTENDING NORTHWARD TO LAKE ERIE AND SOUTHWEST
   TO EASTERN TEXAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLGT AND ENH RISK AREAS...

   CORRECTED FOR GENERAL THUNDER OUTLINE AREA

   ...SUMMARY...
   Thunderstorms -- including risk for wind damage, large hail and a
   few tornadoes -- are expected from parts of the Ohio Valley
   southwestward into the mid and lower Mississippi Valley and
   Tennessee Valleys, and into the southern Plains. An enhanced threat
   for wind damage may occur across parts of the lower Ohio/mid
   Mississippi/Tennessee Valleys.

   ...Synopsis...
   An energetic short-wave upper trough -- phased with a weaker system
   crossing northern Mexico at the start of the period -- will sweep
   across the Plains and into the Great Lakes and Midwest/Ohio Valley
   today and tonight.  Flanking the progressing trough, ridging will
   persist over both the western and eastern portions of the country.

   At the surface, a low is forecast to deepen with time while shifting
   northeast out of the Kansas/Oklahoma vicinity across Missouri and
   into the Midwest through the day.  In conjunction, a sharpening cold
   front will sweep southeast across the central U.S. a the leading
   edge of a surge of cold Canadian air.  By early evening, the front
   should extend from the low -- over the northern Indiana vicinity --
   southwest across the lower Ohio and mid Mississippi Valleys and into
   east Texas, with a band of showers and thunderstorms in the vicinity
   of the advancing boundary.  By the end of the period, the front will
   likely be cresting the Appalachians, while convection will likely
   have weakened to below severe levels.

   ...Lower Great Lakes southwest to parts of eastern Texas and the
   lower Mississippi Valley...
   As surface low pressure deepens/shifts northeastward toward the
   Midwest through the day, low-level warm/moist advection will allow
   the spread of higher theta-e air to advance into the Midwest/Ohio
   Valley ahead of the progressing cold front.  With the associated
   upper system remaining well to the west through the day and thus
   little to no height falls during the day, capping should largely
   hinder convective development within the pre-frontal warm sector.

   By 20 to 21Z, both operational NAM and GFS runs along with most CAMs
   do initiate pre-frontal storms over East Texas, despite the forecast
   capping within the warm sector.  Should this convection develop, and
   in cellular manner, very large hail would be possible given the
   degree of CAPE.  More likely however, storm development will await
   the frontal approach, and become largely anafrontal with time. 
   Still, risk for hail and locally damaging winds is evident, along
   with a tornado or two, as storms evolve and spread eastward into the
   lower Mississippi Valley area and -- eventually -- the central Gulf
   Coast states.

   Farther north, weaker instability but stronger flow aloft -- and
   stronger ascent -- is anticipated, particularly into the late
   afternoon and evening hours as the front sharpens ahead of the
   quickly advancing upper system.  Given the aforementioned capping in
   the warm sector, storms initiating near the boundary should quickly
   grow upscale into at least broken linear mode, with damaging winds
   to become the primary severe risk.  Some hail will be possible,
   along with a few tornadoes -- especially with initial, possibly more
   cellular storm mode.  As convection grows upscale, strong
   west-southwest flow aloft suggests fast storm motion and potential
   for relatively widespread damaging winds.  The corridor for the
   greatest damaging-wind risk -- corresponding with the ENH risk area
   -- will likely be concentrated from southern Indiana/southwest Ohio
   southwestward into the Mississippi Delta region.

   By mid to late evening, gradual/diurnal weakening of convection is
   expected, with severe risk to wane into the overnight hours as
   convection reaches the Appalachians.

   ..Goss.. 04/03/2018

[Holston_River_Rambler]

I saw Michael Ventrice on twitter say he thought this was going to be the biggest outbreak so far this year, but I suppose he could have been hyping to get followers.  I just don't know enough about looking at severe parameters to tell how significant this looks.  Also since I'm on the other side of the plateau and all this looks to be moving W - E, usual that means everything has consolidated and weakened by the time it gets to the eastern valley. I was surprised by the T-storms this morning and maybe that indicates the atmosphere is a little more prepped that it may seem at first glance?  At work in Harriman right now and there are a lot of clouds here and that usually (but not always) spells stability, at least for my neck of the woods. But looks like the deck is starting to break up on GOES 16. 

[jaxjagman]

Been kinda busy today or i'd post more.Tornado watch for Western Valley

 

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 27
   NWS Storm Prediction Center Norman OK
   135 PM CDT Tue Apr 3 2018

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Much of Arkansas
     Southern and East-Central Illinois
     Southwest Indiana
     Western Kentucky
     Southeast Missouri
     Northwest Mississippi
     Western Tennessee

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

   * Primary threats include...
     A few tornadoes likely with a couple intense tornadoes possible
     Widespread damaging winds and isolated significant gusts to 75
       mph likely
     Widespread large hail and isolated very large hail events to 3
       inches in diameter likely

   SUMMARY...Thunderstorms are expected to rapidly form along a cold
   front this afternoon and track across the watch area.  Very strong
   wind fields and instability suggest the potential for fast-moving
   severe storms capable of large hail, damaging winds, and tornadoes. 
   Strong tornadoes will be possible with the most intense storms.

   The tornado watch area is approximately along and 105 statute miles
   east and west of a line from 40 miles south southwest of Hot Springs
   AR to 65 miles north of Evansville IN. For a complete depiction of
   the watch see the associated watch outline update (WOUS64 KWNS
   WOU7).

[nrgjeff]

Well I was just poo-pooing the MDT on a PM. Prefer ENH for wind but we have potential. Indeed appears a slight wind shift in Middle Tenn. Could we get a pre-frontal trough going? Upstairs it does appear the LLJ will increase around 00Z. It is not a strong as up north, but it does strengthen over much of Tenn. I will keep my chips on straight wind, and perhaps several reports, but we'll see. It is April!

[Calderon]

HSV gusted to 61kts.

[nrgjeff]

Looking ahead the MJO is forecast to die off leaving the North American atmo hanging in a cold phase. However we are on week 6-7 of a cold pattern. Going much past 8 weeks would be a shocker even after a SSW hangover.

During the SSW hangover most systems have been too cold (except March 19 and April 3). Day 6-10 severe ends up 1-5 day cold rain. Severe enthusiasts want that to stop.

Weeklies are not as cold starting week 3, but still show meandering troughs. Twice this season Dixie had severe with mean troughs on both coasts, but we can't have a full latitude trough in the East. In the severe episodes the West system regrouped sliding into Dixie.

[jaxjagman]

On 4/6/2018 at 12:23 PM, nrgjeff said:

Looking ahead the MJO is forecast to die off leaving the North American atmo hanging in a cold phase. However we are on week 6-7 of a cold pattern. Going much past 8 weeks would be a shocker even after a SSW hangover.

During the SSW hangover most systems have been too cold (except March 19 and April 3). Day 6-10 severe ends up 1-5 day cold rain. Severe enthusiasts want that to stop.

Weeklies are not as cold starting week 3, but still show meandering troughs. Twice this season Dixie had severe with mean troughs on both coasts, but we can't have a full latitude trough in the East. In the severe episodes the West system regrouped sliding into Dixie.

Yup,i agree.Asia is crapping out on today's models in the long range,like you said though there is more potential for a storm around the 20-21st which what the weeklies are showing,but this might be just a brief lull and maybe a more pattern change?.CFS has been trending warmer towards the end of the month.Also we've seen some outbreaks when the MJO gets into the  IO 8-10 days later but the MJO on the Euro is active while the GEFS wants to crash it into the COD but this is typical GEFS trying to stay out of the IO.But the Euro shows it relative strong until it gets into 3 and then goes into the COD.Nothing is imminent right now due to the lagging SSW,it's throwing off any severe percursors you mentioned.But i'd watch this system around the 20-21st,it has potential

[jaxjagman]

There's a chance,we'll see

[jaxjagman]

Chance for some thunderstorms the end of the week.Euro has better instability right now.Best chance of severe would be in the Western Valley,right now.

 

 Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0354 AM CDT Sun Apr 08 2018

   Valid 111200Z - 161200Z

   ...DISCUSSION...
   The primary feature of interest during the extended period will be a
   deep/amplified mid-level trough that will reach the central US by
   D6/Fri. As it does so, strengthening west/southwesterly flow aloft
   will transport steep lapse rates over much of the southern/central
   Plains. Meanwhile, a robust low-level mass response will feature a
   narrow corridor of enhanced poleward theta-e transport, generally
   from eastern Texas to the lower Missouri Valley. As a dry line and
   cold front accelerate east across the region, low/mid-level ascent
   is forecast to strengthen sufficiently to overcome convective
   inhibition and promote thunderstorms from eastern Texas to parts of
   the Midwest through Friday night. 

   While medium-range guidance continues to exhibit run-to-run
   variability with regards to the amplitude/timing of the trough, most
   deterministic/ensemble guidance suggest strong/severe thunderstorms
   will be most likely from eastern Texas to the Ozarks and Mid-South
   Friday afternoon through the overnight. Within this corridor,
   vigorous low/mid-level wind fields should overlap adequate
   surface-based buoyancy, such that all severe hazards may be possible
   with maturing convection. Therefore, a 15-percent probability has
   been introduced with this forecast cycle. Further refinements of
   this area (with some potential for a northward expansion) will
   likely be needed in future updates.

   The trough will advance further east through D7/Sat-D8/Sun, with
   pockets of strong/severe convection potentially persisting across
   areas from the Ohio Valley south to the Gulf Coast. Despite this
   potential, uncertainties regarding availability of adequate
   instability, the eastward evolution of the trough, and subsequent
   timing/placement of stronger convection remain too high to introduce
   probabilities beyond D6/Fri.

   ..Picca.. 04/08/2018

[nrgjeff]

Enhanced Risk for North Alabama Saturday / tomorrow. Gee, it must be mid-April in Dixie! System will not have much directional shear at upper levels, but surface to mid-level (700 mb) turning is good. Plus we have decent CAPE near the peak of Dixie Alley season. That said, I expect a squall line with mainly straight wind.

Models have shown glimmers of a wave along the front, or even meso-low, in Alabama. Such a feature would create a locally chasable target iff over decent terrain. Central Alabama won't work, but parts of North Bama would. North Alabama issue is possible midday rain stabilizing everything though. Atmosphere does not have that April feel.

No outing is planned for me attm. Enjoying warm temps ahead of the front might be a better use of time. 

The April 22-ish storm is still on the models. Saturday (tomorrow) and 4/22 seem to take warmer tracks. Then the GFS 11-15 day goes back into March weather; and, Euro Ensembles plus both weeklies concur. Hopefully that dreadful late April forecast is wrong, esp in the wake of warmer systems.

UPDATE (for Saturday): 1730Z SPC Day 2 uses stronger words/hatches. While CAMs have mean looking storms, LLJ 850/925 mb wind speed forecast is not particularly robust for this time of year. Direction is there 700 mb under, but not speed. Plus it's unidirectional farther up (though strong). A meso-feature and outflow would make up for all above deficiencies. Plus if no midday rain-out the CAPE instability will be there. Still no chase planned for me - a lot has to happen - but I will keep an eye on the mesoscale situation.

UPDATE 2 for Saturday: Hello 12Z Euro (Fri) and your robust low level jet LLJ. OK, give me an outflow boundary Saturday and we might talk. OFB would be from morning/midday rain Middle Tenn that does not spread into Alabama. Still a big, we'll see, for me.

[jaxjagman]

Seems like the potential for a strong system around the 1st of May,though this could be occluded by the looks.The SOI has recently made some wild swings recently,but it's shown to have made around a 36 point drop recently.The BSR maps shows a cold front with a warm front lifting ahead.Now we also see in the long range looking into Asia(Korea),we see this potential from the Euro.We'll see.

 

[jaxjagman]

As  expected also as mentioned a few days ago the GEFS showed the MJO crashing into the COD when getting into Africa(phase 8),this is GEFS biased.It's a hater of the IO.It's -2 sigma into the IO

 

[nrgjeff]

Saturday was such a dud. I figured it was not a chase day, obvious line of storms, but I was hoping for something a little more interesting to track. Only thunder was in the evening well after the initial band.

April 22 now looks like rain not severe, perhaps cool rain again. Sigh..

First of May indeed a ridge followed by trough is forecast to track from the Plains through the Mississippi Valley. Approaching trough could gin up something in the Tennessee Valley; or, it could dig into a mean East trough and be cool. Too far out for details, but I'm continuing Jax's thoughts. Perhaps the system would be warmer in early May..

[jaxjagman]

20 hours ago, jaxjagman said:

Seems like the potential for a strong system around the 1st of May,though this could be occluded by the looks.The SOI has recently made some wild swings recently,but it's shown to have made around a 36 point drop recently.The BSR maps shows a cold front with a warm front lifting ahead.Now we also see in the long range looking into Asia(Korea),we see this potential from the Euro.We'll see.

 

Edit:Put the wrong BSR map up.Had 4-1 and put the right one up.5-3,either way it's still around the first of May we are talking about

[jaxjagman]

IMME , precip for May.Would seem to be a active month if  it were to be right.

 

[nrgjeff]

Pattern may open the door for severe in our Region about a week into May, iff the system does not dig into a cold bowling ball. In May you'd think we'd have a warm sector! Ensembles have a system traversing the CONUS. Weekly charts have a warmer look week 2 but an East trough week 3. I infer the transition is our system; so, ensembles and weeklies are somewhat in sync.

MJO is forecast to go into more favorable phases deeper into May if the GLAAM stays low/Nina which may be a tough forecast 3-4 weeks out. If the MJO forecast is right it could bring one more chance to the Southeast. However, the above signal shifts into the Plains late May. If either the MJO or AAM fail, May could revert back to the quiet cool regime.

[jaxjagman]

4 hours ago, nrgjeff said:

Pattern may open the door for severe in our Region about a week into May, iff the system does not dig into a cold bowling ball. In May you'd think we'd have a warm sector! Ensembles have a system traversing the CONUS. Weekly charts have a warmer look week 2 but an East trough week 3. I infer the transition is our system; so, ensembles and weeklies are somewhat in sync.

MJO is forecast to go into more favorable phases deeper into May if the GLAAM stays low/Nina which may be a tough forecast 3-4 weeks out. If the MJO forecast is right it could bring one more chance to the Southeast. However, the above signal shifts into the Plains late May. If either the MJO or AAM fail, May could revert back to the quiet cool regime.

Chance for a KW week 3-4 as you mentioned also.Upper trough being shown right now won't be much of any severe weather in the Valley upcoming unless that changes

[jaxjagman]

On 4/15/2018 at 5:13 PM, jaxjagman said:

Seems like the potential for a strong system around the 1st of May,though this could be occluded by the looks.The SOI has recently made some wild swings recently,but it's shown to have made around a 36 point drop recently.The BSR maps shows a cold front with a warm front lifting ahead.Now we also see in the long range looking into Asia(Korea),we see this potential from the Euro.We'll see.

 

The frontogenesis on the Euro on May 1st looks fairly close to the BSR maps,only problem is the split flow right now.The BSR maps look well right now.Severe threat seems low right now into the first part of May,in the Valley

[jaxjagman]

 If  the BSR map is correct we could be looking at the potential for some good storms into week 2 of May.The Dashboard is all over this time frame.Along with the BSR maps shows a area of LP coming out of Texas into the Valley.The OLR has been showing up on this time frame as well.We'll see

 

 

[jaxjagman]

If the GAAM into the May don't get taken out like Jeff mentioned.The GAAM is showing almost -3.5 sigma,this is the same time frame mentioned above,once again,we'll see