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Tn Valley Severe Weather


jaxjagman
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Starting Monday it looks cooler again, perhaps for most of next week with scattered thundershowers. Tuesday is currently the day models/NWP highlights for heavier storms in the Valley, but it has shifted around. 36 hours ago NWP favored Monday.

At any rate a synoptic system with quality upper level wind fields is forecast early next week for the Valley. Looks mainly eastern half of our region perhaps Tuesday. GFS has upper level wind speed but mostly same direction. Euro has more turning upstairs, upper system a bit more open. If it rains the day before, chance of an outflow boundary increases. If timing changes it could be Mid Atlantic (per NWP 36 hours ago). Finally we'll see if the wind field forecast holds up.

Most days with thundershowers should not be severe. Over five days we should be able to absorb that QPF without major flooding concern, at least in Tenn. However the devil is in the local details. Local flash flooding is always possible with thunderstorms. Also with sustained southeast flow, Georgia and up the Blue Ridge could have a lot more precip.

 

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11 hours ago, *Flash* said:

This summer has come full circle from winter. I.e. I can buy into the temps, but I'll believe the precip when I see it the way my lawn is goin...

Nashville is going with the Euro.Euro has a shortwave trough coming through the Mid Valley,late night,early morning Tuesday.Wind shear looks weakish right now but at least should be enough for a poor mans severe chance with just thunderstorms,showalter is around -4,in the Mid Valley.

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Euro is slightly different today for us in Mid Tn. from yesterday this time.Monday looks more scattered with weak wind shear but there is a weak shortwave trough coming through..Into the late evening into early morning Tuesday the LLShear starts to pick up.Kinda question the capes the Euro shows with the CAMS,Tuesday.But anyways the LL shear is showing 20 kts into the early afternoon into the early evening here,with the 850mb winds increasing to around 35kts around late afternoon,with another shortwave trough coming though.There would be some decent rains Tuesday afternoon into early evening here at least,if it's right of course.If the CAMS get better we'll have more severe chance.

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  • 2 months later...
19 hours ago, nrgjeff said:

The increase in tornado activity on the Delta is convenient because it is flat. However that is just change (delta on the Delta, lol). The Delta is still a local min within Dixie Alley. Maybe it will change.

Do you have access to this?Would like to know a little more about the paper,just don't want to spend $35 :( Not sure if i should ask you that question but i thought i'd give it a shot :)

 

Abstract

The El Niño-Southern Oscillation (ENSO) and Gulf of Mexico (GoM) influence winter tornado variability and significant tornado (EF2+) environments. Increases occur in the probability of a significant tornado environment from the southern Plains to Midwest during La Niña, and across the southern contiguous United States (CONUS) during El Niño. Winter significant tornado environments are absent across Florida, Georgia, and the coastal Carolinas during moderate-to-strong La Niña events. Jet stream modulation by ENSO contributes to higher tornado totals during El Niño in December and La Niña in January, especially when simultaneous with a warm GoM. ENSO-neutral phases yield fewer and weaker tornadoes, but proximity to warm GoM climate features can enhance the probability of a significant tornado environment. ENSO intensity matters; stronger ENSO phases generate increases in tornado frequency and the probability of a significant tornado environment, but are characterized by large variance, in which very strong El Niño and La Niña events can produce unfavorable tornado climatological states. This study suggests that it is a feasible undertaking to expand spring seasonal and subseasonal tornado prediction efforts to encompass the winter season, which is of importance given the notable threat posed by winter tornadoes. Significant tornadoes account for 95% of tornado fatalities and winter tornadoes are rated significant more frequently than during other seasons.

https://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-18-0046.1

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19 minutes ago, John1122 said:

Good article,thanks John.I was wanting to know more what her findings were about in Dec. or late autumn into early winter.We are a time time in an El Nino year where tornado activity starts to spike and actually we are only a few weeks to where it peaks in fall severe.

How does El Nino  La Nina or La Nada impact the following tornado season    U S  Tornadoes.png

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Nice system like we talked about in the fall thread last week with the trough going through East Asia and Yutu not re-curving and going into the Phillippines but there still was the trough either way.Storm starts to go -ve tilt somewhere around the Central plains.Would be a nice system but still a long way out but still nice it has some backing

 

ecmwf_z500a_namer_8.png

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I'll go with the ECMWF Euro as usual. Either way it is rainy crap weather on Election Day. Consider early voting if not already done, weighing the next two days also. Halloween is today and looks like rain tomorrow (Thursday) which is the last day of early voting. I respect no politics on the weather board; we love weather first. Just a note on weather related logistics. Happy and safe Halloween!

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I'll go with the ECMWF Euro as usual. Either way it is rainy crap weather on Election Day. Consider early voting if not already done, weighing the next two days also. Halloween is today and looks like rain tomorrow (Thursday) which is the last day of early voting. I respect no politics on the weather board; we love weather first. Just a note on weather related logistics. Happy and safe Halloween!

Thanks, Jeff! No need to remind when you are merely being informative about what to expect weather-wise while people are out exercising their right as citizens. Hopefully no severe variety storms or high wind impact events, and crap rain is all anybody has to deal with that day.

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Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0407 AM CDT Fri Nov 02 2018

   Valid 051200Z - 101200Z

   ...DISCUSSION...
   Potential exists for a significant severe event to transpire day 4
   (Monday) into day 5 (Tuesday) mainly from the lower MS Valley into
   the Southeast States. Model solutions have converged and
   demonstrated run to run consistency, depicting significant
   cyclogenesis to commence by Monday evening over the lower MS Valley
   in response to an approaching intense upper jet within base of an
   amplifying shortwave trough. The low is forecast to deepen as it
   lifts northeast into IL overnight with trailing cold front advancing
   through the TN and lower MS valley regions. Richer low-level
   moisture residing over the northern Gulf will advect rapidly
   northward through the warm sector in response to the strengthening
   low-level jet, contributing to destabilization with moderate
   instability possible from east TX into a portion of the Gulf Coast
   states. Severe storms are likely to develop along advancing cold
   front Monday afternoon initially from southeast OK into east TX,
   then spreading into the lower MS Valley and TN Valley regions Monday
   night. Impressive wind profiles with large hodographs and an intense
   upper jet will promote a threat for damaging wind, tornadoes and
   large hail. Severe threat will continue east through portions of the
   Southeast states and Middle Atlantic Tuesday.
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  • 2 weeks later...
23 hours ago, nrgjeff said:

European weeklies have a possible pattern the week after Thanksgiving week; so, a little later into the end of November.

Some of the long range models don't really show much of a warm up now,guess we'll see,think the date you are talking about is around the 28-29 ?Right now looks more winter than severe

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  • 2 weeks later...

Like John brought up in the winter threads a potential severe threat would be this coming Saturday.The question would be what kind of convection happens south of us which could choke off instabilities.But this system is starting to look like the system we saw earlier this month with a nose of cape  with some very good helicities like the GFS shows this afternoon.

pivotalweather   GFS   Energy Helicity Index  EHI   0 3 km AGL for Sun 2018 12 02 00z.png

pivotalweather   GFS   Storm Relative Helicity  SRH   0 3 km AGL for Sat 2018 12 01 18z.png

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ECMWF remains consistent with a chance of severe weather Friday night and Saturday from the Mid-South to the eastern Tennessee Valley. Many details need to work out from instability to short-wave timing. Looks like multiple waves, which can giveth or taketh away. I infer from the text SPC really wants to outlook Saturday, but I agree it would be hard to place the 15%.

Too early to worry for those who dislike severe. Just those of us who like it, we want to track it. Honestly, at Day 6, it is not any more likely than snow in Dixie, lol!

PS.. I will comment on December after the ECMWF weeklies update. Maybe I should have stayed with Carver for Dec. Did I go cold too fast?

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1 hour ago, nrgjeff said:

ECMWF remains consistent with a chance of severe weather Friday night and Saturday from the Mid-South to the eastern Tennessee Valley. Many details need to work out from instability to short-wave timing. Looks like multiple waves, which can giveth or taketh away. I infer from the text SPC really wants to outlook Saturday, but I agree it would be hard to place the 15%.

Too early to worry for those who dislike severe. Just those of us who like it, we want to track it. Honestly, at Day 6, it is not any more likely than snow in Dixie, lol!

PS.. I will comment on December after the ECMWF weeklies update. Maybe I should have stayed with Carver for Dec. Did I go cold too fast?

Nah, man.  I think you all will be right.  If that cold is anywhere close to being what is on the EPS, I have a difficult time seeing the back half of December getting us back to normal.  Same deal with this month.  

As for severe, I just want some decent wind to knock these last leaves down.  Today has been good for that.  Right now, I still have like two more weeks of leaves thanks to this tree in my front yard!  It always drops them last.  

Also in terms of severe(pretty much a novice on my part), but I thought today how strong this front was that brought in the cold.  Seems like we are in a pattern with strong fronts and those can definitely favor storms.  We are also in the time frame where I think if we see severe near the mountains that snow follows within two weeks...or something like that.

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Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0226 AM CST Tue Nov 27 2018

   Valid 301200Z - 051200Z

   ...DISCUSSION...
   Though minor differences in amplitude exist, ensemble members are in
   good agreement regarding a progressive shortwave trough that is
   forecast to advance through the lower MS and TN Valley regions
   Friday night (day 4) into Early Saturday (day 5). Modifying air from
   the Gulf with mid to upper 60s F dewpoints will advect through the
   lower MS Valley warm sector Friday resulting in marginal
   near-surface based CAPE within a weak lapse rate environment. Areas
   of clouds and a few showers and thunderstorms will likely be in
   progress along warm conveyor belt during the day, and this lowers
   confidence in degree of destabilization. Winds aloft and vertical
   shear will strengthen overnight, becoming supportive of organized
   storms including supercells with damaging wind and a few tornadoes
   possible. For Saturday (day 5) though some severe threat may linger
   ahead of the advancing cold front from the Gulf Coast states into a
   portion of the TN Valley, tendency will be for the stronger winds
   aloft and deeper forcing to gradually move away from the more
   unstable portion of the warm sector. This along with ongoing
   widespread precipitation, lowers overall confidence in degree of any
   severe threat at this time.
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4 hours ago, John1122 said:

The local Christmas parade is Saturday evening around 6 but there will be lots of float and parade prep from 3-6 as well. I'm hoping we can avoid the severe during that time frame if we can't avoid the rain.

Realized the same thing this afternoon.  Same deal here.  Any updates on timing for the forum area would be great.  

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