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jaxjagman

Tn Valley Severe Weather 2018-19

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Thursday looks like a mess with JIT moisture and a monster MCS cutting off everything anyway.

Weekend (Sunday?) looks better. Moisture will already be in place as the Friday front never clears the Gulf. Upper winds may have VBV issues; but, at least it'll be more unstable.

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Sunday the ECMWF shows another Gulf MCS keeping Dixie Alley quiet. ECMWF continues a Texas MCS which might not exactly dive to the coast. ECMWF upper levels are suspect, but match the surface scenario. The following is based on the GFS/NAM. 'Murica yeah!

The 200/300 mb level winds are little weak and erratic; however, 500 mb is robust and more west than south. Otherwise surface to 700 mb shows pretty good turning. Hodograph is a mess above 500 mb; but, it looks great from 700 mb down. Instability is forecast across Mississippi and Alabama into Georgia. I'm not sure about Tenn.

Pattern recognition and some models have a boundary lifting through Alabama. It's left over from the Thursday/Friday system. Front never makes to the Coast. It should lift back as a warm front with quality moisture. Sunday is being monitored for a possible chase. If the ECMWF is right I'll instead be relaxing with family in Chattanooga, lol!

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Certainly  a chance of hail  and wind Sunday.NAM is being shown as the outlier in which it should be 

MJO ,seems possible it gets into the IO wk2.but after that?

 

 Chance for a decent system in the long range as the PNA goes negative but at the same time there finally could be a more negative NAO that everyone was waiting on this winter,this would be more or less a suppressed storm track like the Euro shows but at the same time say "Hello" to April showers with potential some serious rain for any part of the Valley especially with any convection

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I’m ok with rain if we can stay pretty mild. Amazing that the creek behind my house is still almost at ground level.


.

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It should be easy to spot the MJO.Other than some desructive interference ENSO signs around the IDL  the MJO is looking stronger as it gets into the IO.No telling beyond that though,

Real Time multivariate MJO Phase Space Diagrams   Michael J  Ventrice  Ph D .png

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Just saying if the MJO gets into the Pacific you could see once again the jet get excited by Enso.This pattern seems to be on going with this ENSO bringing  LP's through the Valley

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8 hours ago, jaxjagman said:

Just saying if the MJO gets into the Pacific you could see once again the jet get excited by Enso.This pattern seems to be on going with this ENSO bringing  LP's through the Valley

Not liking, not that any of us would, the wet pattern that seems to be being telegraphed by long range modeling, not to mention the severe threats!

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Late April we hope that awful convection in the West Pac dies. Some models forecast the IO to refire, which puts the North Pac ridge in the correct place for a West USA trough. Unfortunately those week 4-6 forecasts have practically zero correlation to actuals. We hope though! Plus May climo is trough West.

As for this weekend: NCAA games and Chattanooga Football Club. 

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Come Monday it'll be alright. Come Monday I'll be holding shear tight. -Jimmy Buffet with some Jeff at the end.

Sunday still looks like a mess. Storms in Middle Tenn are trying to create their own LLJ but warming 700 mb will end the party. Just hope the non-severe junk holds off for my Sunday outdoor plans in Chatty.

Monday looks intriguing in northwest Georgia, but that terrain! Low level shear should be good east of the surface low and triple point. Upper shear is suspect. Reminds me of June around here. IDK if it's worth a chase. Maybe hang out on the view deck of Ft Mountain State Park and hope to see something.. without getting struck by lightning!

Might be better to watch the NCAA National Championship on Monday. Go Texas Tech!

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Looks like the nasty cell that flared up between Newport and Parrottsville verified its SVR. MRX received a report of 1.5" hail in Greene County.

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Palm Sunday is the elephant in the room, so I'll address it. It's Day 7. Done. 

OK seriously, the GFS verbatim only shows ENH due to unidirectional winds, lots of rain, and likely coastal MCS. ECMWF verbatim is MDT no sugar coating it. However neither are high, thanks to moisture concerns, and possibly energy ejecting too far north.

Still Day 7 so lots can change. Might end up Marginal, lol. Ways to get there include heavy rain on unidirectional winds or some sort of Gulf MCS.

Little closer in I figure Thursday will have moisture issues. Upper dynamics displaced too far north. Maybe low-top Illinois Indiana but that's another subforum region.

And today? I think those Gulf thunderstorms don't qualify as enough for an MCS bust. SPC leans toward it weakening (MD 287) which would keep North Alabama in business later. CAMs are weak with low level shear; but, pattern recognition shows outflow boundary east of surface low. Dixie gonna Dixie?

UPDATE: Central Alabama BHM south, which is out of our regional subforum. NCAA Final is my evening plan.

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Event thread for April 13-14 weekend severe wx outbreak is in Central/West. Thread subtitle includes Mississippi, my likely chase target Saturday. My thoughts are in that thread. Basically with less morning rain in Mississippi, the warm front should lift north more. I expect discrete cells along the WF and/or outflow boundaries. 

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 Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Fri Apr 12 2019

   Valid 141200Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
   OHIO AND WEST VIRGINIA SOUTHWARD INTO THE SOUTHEAST...

   ...SUMMARY...
   Strong/severe thunderstorms are anticipated Sunday -- centered over
   the mid and upper Ohio Valley, and central and southern
   Appalachians.

   ...Synopsis...
   A strong mid- and upper-level trough exiting the Plains early in the
   period is expected to advance steadily east across the
   Mississippi/Tennessee/Ohio Valleys and central Gulf Coast states,
   reaching a position from the lower Great Lakes to the southern
   Appalachians/Southeast late in the period.

   At the surface, a deepening low is forecast to shift east-northeast
   across the Ohio Valley through the day, and then across the central
   Appalachians to the Hudson Valley vicinity by the end of the period.
   Widespread thunderstorms -- and a broad severe risk -- will
   accompany this system.

   ...The Ohio Valley and central Appalachians south to the
   Southeast...
   Showers and thunderstorms are forecast to be ongoing in a
   north-south band from Indiana to Alabama early in the period, ahead
   of the advancing cold front.  As modest heating of a moistening
   pre-frontal warm sector commences, 500 to 1000 J/kg mixed-layer CAPE
   is expected to evolve ahead of the ongoing band of convection, from
   the Ohio Valley to the Gulf Coast.  This should result in a gradual
   intensification of storms through the afternoon, aided by a very
   strong deep-layer wind field accompanying this storm system --
   including 80 to 100 kt south-southwest flow at mid levels.

   Primary storm mode is progged to be banded/loosely linear, with
   embedded/complex bows and rotating updrafts.  Damaging winds will
   likely be the primary threat, though tornadoes will also be possible
   across much of the area -- particularly near and west of the
   mountains.  Risk should diminish gradually through the evening,
   though local wind risk may persist through the end of the period.

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The NAM is slower than the GFS.This pattern we are stuck in seems to be we see systems come in faster than being shown,but we'll see.GFS shows the LLJ strenghten into Mid Tn to around 60-70kts with low capes and high helicities we should have the potential to see more mesocyclones.Not really sure but i think the enhanced could be shifted further west next update,if the NAM is right we'd see more capes,but the bias SLOWER NAM outside 24 hrs..,believe the GFS might be right.

gfs_mslp_uv850_us_6.png

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1 hour ago, jaxjagman said:

The NAM is slower than the GFS.This pattern we are stuck in seems to be we see systems come in faster than being shown,but we'll see.GFS shows the LLJ strenghten into Mid Tn to around 60-70kts with low capes and high helicities we should have the potential to see more mesocyclones.Not really sure but i think the enhanced could be shifted further west next update,if the NAM is right we'd see more capes,but the bias SLOWER NAM outside 24 hrs..,believe the GFS might be right.

gfs_mslp_uv850_us_6.png

In the latest update, the enhanced risk didn’t shift west, but it did expand west some. Here’s the latest from the SPC:

 
...Mid and upper Ohio Valley and central Appalachians, southward
   into the Southeast...
   A semi-continuous, roughly north-south band of thunderstorms is
   expected to be ongoing at the start of the period, extending from
   southeastern Indiana/southwestern Ohio southward to the
   Alabama/western Florida Panhandle coasts; while this will likely be
   a period of relative minimum in severe risk, local risk for damaging
   winds/hail, and possibly a tornado or two, will likely be ongoing.

   As the airmass ahead of this initial band destabilizes into the
   afternoon, storms are expected to reintensify.  Damaging winds and
   some tornado risk may spread across the middle and into the upper
   Ohio Valley through the afternoon with this band of storms. 
   Meanwhile near and east of the southern Appalachians,
   reintensification of convection in this band may become more
   cellular in organization.  Given favorably strong flow through the
   lower and middle troposphere contributing to strong shear, this more
   cellular storm mode would support risk for a few tornadoes, along
   with locally damaging winds and some hail.

   In the wake of this initial band of storms, modest destabilization
   is expected, likely leading to development of a second band of
   storms nearer the surface cold front.  As this band of storms
   crosses the middle Ohio Valley/Mid South region, severe risk is
   anticipated, with damaging winds and tornadoes both possible given
   the very strong shear residing atop the pre-frontal boundary layer. 
   Risk in any area will be somewhat storm-mode dependent, with a mix
   of cellular and banded structures possible within the north-south
   zone ahead of the front.

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National Weather Service Nashville TN
641 AM CDT Sat Apr 13 2019

.UPDATE...
FOR 12Z AVIATION DISCUSSION.

&&

.DISCUSSION...

Early this Saturday morning, scattered light showers were
occurring over the southeast half of Middle Tn. These showers were
located along a stalled frontal zone. The front will begin to
lift northward today, spreading scattered showers across the area.
Isolated thunder will develop late morning through the afternoon,
but no severe wx or heavy rainfall is expected today. In fact,
forecast rainfall amounts are less than one quarter inch.

Back to our southwest, a few powerful thunderstorms were raging
in East Tx and La early this morning. These had developed in
response to a strong trough moving out of the southwest states
into Tx. Over the next 36 hours, the big trough will move to the
Ms Valley as a surface low deepens and moves northeast to the
Ohio Valley. The result will be an outbreak of severe
thunderstorms across the Lower Ms Valley Region today, with these
storms shifting northeastward to the Tn Valley Region late tonight
into Sunday morning. On Sunday the focus for storms will spread
from the Tn Valley across a large part of the Appalachian Region.

There continue to be uncertainties about the exact timing and
evolution of the thunderstorms across Middle Tennessee. We do feel
confident there will be a wave of storms coming in from the
southwest late tonight and crossing the area very late night
through Sunday morning. Then, there will be some additional
thunderstorm development along a cold front midday into Sunday
afternoon. For simplicity- severe thunderstorms will be possible
from midnight tonight until 6 PM Sunday. The late night and early
morning threat will be area wide, while the Sunday afternoon focus
will be east of I-65. Most of the area is under a slight risk,
with the eastern third under an enhanced risk. These risk areas
will likely be adjusted a bit through the next 24 hours. I would
not focus on these nuances- the main story is that all of Mid Tn
could have severe thunderstorms with damaging winds, large hail,
and a few tornadoes. Prepare now for what you will do if a tornado
warning is issued - or a severe thunderstorm warning for powerful
winds - and make sure you have ways to receive warnings.

Forecast parameters showing 300-500 J/kg CAPE late tonight, increasing
to around 1000 by mid morning Sunday as dew points climb into the
low to mid 60s. 0-6km layer shear is well over 50KT with 850MB
winds reaching over 50KT around 12Z. Like any severe storm
forecast, this is no slam dunk, but this deepening, very dynamic
system certainly has the potential to create damage from all modes
of severe wx. Strong winds outside thunderstorms will also be a
concern with some gradient wind gusts over 40 mph at times. Some
heavy downpours are possible, mainly with the late night storms,
but we think fast storm motion with help limit the flood threat.
Generally, 1 to 2 inches of rainfall is expected with some locally
greater amounts.

All the action will decrease and/or move east of our area by
Sunday evening. Monday looks dry and cooler, then a warmup with
return flow Tuesday. Rain chances will return starting late Wednesday
with strong thunderstorms possible by Thursday as another big low
pressure system crosses the region.

&&

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Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0757 AM CDT Sat Apr 13 2019

   Valid 131300Z - 141200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
   EAST TEXAS...CENTRAL/NORTHERN LOUISIANA...SOUTHEASTERN
   ARKANSAS...AND WESTERN/CENTRAL MISSISSIPPI...

   ...SUMMARY...
   Tornadoes -- some potentially strong to violent (EF2+) -- are
   possible today from east Texas to central Mississippi.  Otherwise,
   numerous severe thunderstorms will pose a risk of large hail,
   damaging wind and tornadoes from central Texas this morning to the
   Tennessee Valley region overnight.

   ...Synopsis...
   In mid/upper levels, a leading/northern-stream perturbation will
   eject northeastward across from its present position over Lake
   Superior and northern Ontario, across Quebec.  To the southwest, a
   deep, high-amplitude trough is evident in moisture channel imagery
   over NM, far west TX, and northern MX.  This trough will pivot
   east-northeastward today, developing a closed 500-mb low by 00Z near
   the DFW Metroplex, and extending southwestward across Coahuila.  By
   12Z, that low should reach eastern MO, with trough southwestward
   over the Arklatex to deep south TX.

   At the surface, the 11Z analysis showed the primary surface low
   along a band of convection south of SJT.  A double structure was
   apparent to baroclinic zones to its east:  the first a
   quasistationary front across central TX to near a SHV-CBM-CHA axis. 
   The southern front was quasistationary just south of UVA and SAT,
   becoming a warm front over southeast TX and south-central LA, then
   quasistationary again over coastal AL and coastal western FL
   Panhandle.

   The primary surface low should deepen and cross the Arklatex region
   late this afternoon into early evening, reaching the lower Ohio
   Valley around EVV by 12Z.  The southern is expected to accelerate
   northward from mid/late morning, to and perhaps past the I-20
   corridor in northeast TX and LA, then over Mississippi, likely
   merging with the northern one.  By that time, a cold front should
   extend from the low south-southwestward across the MS Coast area,
   likely preceded by an organized quasi-linear MCS over the Deep
   South.

   ...TX to Lower Mississippi Valley, Mid-South and TN Valley...
   A regional outbreak of severe thunderstorms, with the main concern
   being damaging tornadoes, still appears possible today in and near
   the categorical moderate-risk area.  Only peripheral adjustments
   were needed for this outlook package, based on convective trends
   this morning and (on the eastern edge) continuity of overnight
   severe potential into the early day-2 period.

   Strong-severe thunderstorms are ongoing across portions of the Hill
   Country southward toward the Rio Grande.  This convection will pose
   a severe threat into central TX through the rest of the morning. 
   Refer to SPC watches 48-49 and associated mesoscale discussions for
   near-term details.

   East of the ongoing activity, the parameter space will become very
   supportive of supercell/tornado potential through the day in the
   warm sector, with the main uncertainties being longevity and
   discreteness of favorable storm mode.  As the southern front moves
   farther inland, a deeply moist boundary layer will spread across the
   region, with surface dew points commonly in the mid/upper 60s F and
   locally near 70, PW 1.5-1.75 inches, and mean mixing ratios
   increasing to 15-16 g/kg, with forecast soundings showing favorably
   low LCL.  Gradual diabatic heating in pockets will weaken already
   meager MLCINH from midmorning onward, enabling storm formation on
   pre-MCS sources for weak lift such as confluence/convergence lines,
   and perhaps persistent/relatively deep horizontal convective rolls. 
   Lapse rates will strengthen with westward extent, supporting
   preconvective MLCAPE ranging from 2000-3000 J/kg over parts of east
   TX to 1000-2000 J/kg over portions of LA and MS.

   Such buoyancy will be more than favorable for all forms of severe,
   amidst strengthening deep shear related to the approach of the
   mid/upper trough.  Furthermore, low-level shear vectors and
   hodograph sizes will be quite large along and south of the warm
   front, with forecast soundings yielding 250-600 J/kg effective SRH. 
   Any sustained supercells in this environment will be capable of
   significant tornadoes.

   With time this evening and overnight, convection should organize
   into a roughly north/south-aligned band over the lower Mississippi
   Valley region, as deep convergence becomes better-focused in the
   mass response ahead of the synoptic wave.  As this occurs, the main
   threat in a bulk sense may become damaging wind tonight.  However,
   given the strong inflow-layer SRH, tornadoes still will be probable
   from both embedded supercells and QLCS mesovortices.

   ...Central/eastern NC and vicinity...
   Widely scattered to scattered thunderstorms are expected to develop
   through this afternoon, offering the potential for damaging gusts --
   perhaps reaching severe limits on an isolated basis -- and isolated
   severe hail.

   Mid/upper-level support will be lacking, beneath a belt of
   southwesterlies aloft.  However, diabatic surface heating amidst
   weak ambient MLCINH should enable only weak lift necessary to
   initiate convection.  The area will straddle a low-level moist axis
   characterized by surface dew points generally in the mid/upper 60s
   F, supporting peak preconvective MLCAPE in the 1500-2000 J/kg range.
   Though low-level flow will be weak, limiting boundary-layer shear
   and hodograph size, the height gradient will remain sufficiently
   tight aloft to support strong storm-relative/ventilating winds in
   upper levels, and effective-shear magnitudes around 40-50 kt.  As
   such, a few organized multicells and sporadic supercell structures
   will be possible.  Convective potential will be strongly tied to the
   diurnal cycle, and should wane precipitously after 00Z.

   ..Edwards/Wendt.. 04/13/2019

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The MJO looks like it's going to show face upcoming into the IO but then potentially go hide back into the COD around the last week of April with some potential ENSO destructive interference it seems.The SOI around the 9-12th of April dropped around 40 points from a more Nina to a Nino pattern.Looks to me we should potentially see a decent system into the first week of May coming off East Asia the last week of April,how teleconnections work out is another thing.

gfs-ens_z500a_wpac_49.png

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CIPS shows the best tornado risk in the SW portion of the Valley,Thursday.Not very many good analogs with this system, for the Valley anyways.

CIPS Analog Based Severe Probability Guidance.png

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Glad nobody started a thread. Today does not deserve one. My first day back since Sunday..

HRRR seems odd with heavy stratoform precip. NAM tries to fire off the back side of line later this evening. LOL at that solution with LLJ cut off and stable atmo.

Line may spit out some straight wind later this afternoon; then, weakens. South Bama could keep going. Spann may have a long night. 

Up here I'm not too concerned. Looking fwd to watching more NBA playoffs.

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19 minutes ago, nrgjeff said:

Glad nobody started a thread. Today does not deserve one. My first day back since Sunday..

HRRR seems odd with heavy stratoform precip. NAM tries to fire off the back side of line later this evening. LOL at that solution with LLJ cut off and stable atmo.

Line may spit out some straight wind later this afternoon; then, weakens. South Bama could keep going. Spann may have a long night. 

Up here I'm not too concerned. Looking fwd to watching more NBA playoffs.

Any thoughts on May from a seasonal perspective? GWO looking increasingly favorable for mid-late May but from this range tough to make any definitive statements 

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Sure seemed like the storms bowed out coming up the valley last night, got some intense wind near blount/knox county line!

54 mph gust as TYS?!

SmartSelect_20190419-061635_Chrome.jpg

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I'm far less optimistic than the Twitterverse. 

23 hours ago, bjc3395 said:

Any thoughts on May from a seasonal perspective? GWO looking increasingly favorable for mid-late May but from this range tough to make any definitive statements 

While the IO is flaring up as expected, the West Pac remains active too. Signal conflict. Expect mixed outcome in the USA. I'm pretty bearish next 15-20 days. Perhaps it switches around for late may peak of climo. I ain't holding my breath. It'd be Plains anyway.

ECMWF weeklies flipped from good to poor about next week a year ago. I'm expecting a repeat. Sorry I am so jaded. Too much early season VBV garbage.

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MJO is moving but slowly by the looks.Even though the RMM'S shows it going into the COD,it should be getting into the Maritime upcoming  .We don't see the same pattern back into late winter with the decent WWB's..The SST'S are still warm and any KW that has come along has been to weak to have much if any influence on this,though you can certainly see cooler waters further down into the thermocline it will still take awhile to mix those warmer waters out closer to the surface.

 

These systems coming through East Asia look weak,and also more ridging into China and Korea,probably more MJO.Euro keeps wanting to build an Omega into the Bering Sea long range.It's not very exciting right now the next several days

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CIPS shows some potential severe storms around the middle of next week,mainly hail and wind.LL/Shear looks weak with some sad looking hodos right now per GFS,

Believe there will be a better system as the models continue to show a trough going through S/Korea,so maybe we'll see some better storms around the 8th give or take like the GFS is showing,right now.

Quote

 

 

ehi03.conus.png

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This date back in 2002 there was an F3 tornado go through Rutherford and Cannon,TN(counties).This was one of two F3's that came through Middle Tn that said year.In Nov. another F3 went through Cumberland, county that claimed four lives with that storm

NWS Nashville Forecast Area Tornado Database.png

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