Severe Weather 2020

[tennessee storm chaser]

I think the biggest problem for the next couple of weeks going forward is that the pattern is a little too active, without stronger ridging just southeast of us. We have too many systems frequently sweeping through with none of them ejecting northeast. They are all sweeping straight across and sending their cold fronts down through the Gulf, and then the next one comes in before there is any time for quality moisture recovery at all. Until/unless that changes, the pattern will be active and there will be dynamic storm systems... telegraphing to us what the pattern is capable of, but there will be very little in the way or appreciable or significant severe weather. IF we get one of these to eject northeast and stall its front out along the Gulf Coast though, it would be game on for the next system right behind it.

if we can get a southeast ridge to pop up and become stubborn, that would help some think fred?

 

[Fred Gossage]

if we can get a southeast ridge to pop up and become stubborn, that would help some think fred?

Yes, but that is a larger scale thing that won't wait until the last minute to show itself, and there are no signs of the wavelengths changing over the next couple of weeks to allow that. The ridge is there; it's just not asserting itself enough. The main thing that would help is if we didn't have as many systems back to back in the wave train, and that shows no signs of changing either. These are large scale issues in the pattern right now that would show signs of fixing themselves if they were going to. What this is doing is showing what the pattern is capable of as we head into the latter part of winter and eventually into spring, as the -PDO continues to mature and the +TNI pattern gets more established. Eventually, we will get changes into the larger scale pattern that will allow greater wavelengths between the systems and better return flow. I'm just doubting more and more that it happens pre-Christmas.

 

[CheeselandSkies]

...which of course is just fine if you don't want your Christmas mucked up by a tornado outbreak...here thinking of the Christmas Day 2012 and 12/23/15 events. Interesting that the latter of those two occurred during the "Super Nino" when a large area of above normal temperatures encompassed much of the eastern and central CONUS (what James Spann termed the "El Nino blowtorch). Above normal December temperatures likewise are occurring and expected to continue in 2020, but we are in an opposite ENSO state.

 

[andyhb]

Need to get a 2021 threat running at some point, but this may have some implications down the road regarding suppression of the SE ridge for a time.

 

[Fred Gossage]

Need to get a 2021 threat running at some point, but this may have some implications down the road regarding suppression of the SE ridge for a time.

I volunteer as tribute. I have several things to point out. But let me do my afternoon weathercasts first so that I can grab graphics...

 

[Fred Gossage]

I volunteer as tribute. I have several things to point out. But let me do my afternoon weathercasts first so that I can grab graphics...

Severe Weather 2021

https://www.tnvalleyweather.com/post/la-ni%C3%B1a-check-up-and-what-it-may-mean-for-the-next-few-months-ahead I will just post the blog article I wrote for our website so that I don't have to type all that out again, and so that I don't have to worry about hosting multiple pictures on here. I...

talkweather.com

Here is the transition over to the 2021 discussion so that we can leave this discussion here for any possible sneak attack that may come before the end of the year.

 

[Fred Gossage]

We still can't count out these systems over the next couple of weeks either. Right now, the main thing that's messing them up in regards to a severe weather risk is that there is very little (if any) ridging off the Southeast coast, and that's allowing all of the departing shortwaves to eject east or even east-southeast, sending their fronts through the Gulf like a brillo pad to scour out the moisture. Then, the next one arrives before even marginal moisture recovery can happen. IF we can get one of these to eject more east-northeast or northeastward, its front would stall near the Gulf Coast, and it would be game on for the next system behind it. It's a good ways out, and there's a lot of uncertainty, but we're starting to see signs that just might happen for the system that's consistently modeled just a few days before Christmas. If systems keep diving east/southeast prior to it ejecting out, there's little to no chance of a severe weather risk. But if the shortwave ahead of it around the 19th-20th ejects more northeast toward the Mid-Atlantic or Northeast, there would be a decent chance of moisture recovery ahead of the 22nd-23rd system. We'll see...

 

[CheeselandSkies]

SPC generally concurs with @Fred Gossage's current thinking, their forecast doesn't quite reach into the near-Christmas timeframe.

...DISCUSSION...
Within a belt of westerlies emanating from the mid-latitude Pacific,
it appears that another significant short wave trough will progress
inland of the Pacific coast by early Monday, before traversing the
remainder of the nation by the middle to latter portion of next
week. While it appears that this feature could support significant
surface cyclogenesis near or east of the Atlantic Seaboard late next
week, medium-range guidance continues to suggest that any surface
cyclogenesis over the interior U.S., east of the Rockies, will
remain modest to weak. A substantive inland return flow of moisture
off the Gulf of Mexico appears unlikely, contributing to the
maintenance of generally stable conditions and low convective
potential.

 

[tennessee storm chaser]

yeah think its time to put our focus on to the 2021 season now. this progressive weather pattern looks continue rest this month least... but 2021 should get interesting severe weather wise as winter moves towards spring especially with the decaying la nina ...

 

[warneagle]

Confirmed large tornado on the ground in Hillsborough Co., Florida.

 

[Fred Gossage]

https://www.wfla.com/newscast/ Live severe weather coverage from WFLA-TV in Tampa...

 

[warneagle]

Yeah, this thing was nothing to sneeze at

 

[warneagle]

Two confirmed tornadoes in the Tampa area yesterday:

 

[akt1985]

Watch the I-10 corridor between Lake Charles and Pensacola for severe storms later today.

 

[warneagle]

Day 2 ENH in eastern NC and far southeastern VA.

 

[warneagle]

Day 1 ENH with a sizeable 10% TOR area. Southeast NC is probably going to be the sweet spot in terms of getting substantial destabilization to go along with the impressive wind fields.

 

[MichelleH]

Spann says we could have storms New Year's Eve, but right now SPC only has a risk for South AL on the day 5. Thoughts?

POTENT STORM SYSTEM TO IMPACT ALABAMA NEW YEARS'S EVE: Look for a warming trend in the days ahead; temperatures could reach 70 degrees by Wednesday across Alabama. Then, a fairly dynamic storm system will impact the state Thursday.
It looks like we will have the dual threat of heavy rain and strong thunderstorms Thursday and Thursday night; rain amounts of at least 1-2 inches are likely, and that forecast could be revised upward if model trends continue, meaning a flash flood threat could develop.
And, most of Alabama will be in the warm sector of the storm system. For now, SPC has South Alabama in a severe weather threat in their "Day 5" outlook for Thursday, and this could be expanded in coming days.
It is really too early for specifics, but just know active/wet/stormy weather is likely across the state Thursday and Thursday night. Rain ends early Friday, followed by colder, drier air. There is no sign of any snow or ice for Alabama as the colder air arrives.

 

[Fred Gossage]

Seeing even the GFS, with the southernmost surface low track, get 60 dewpoints up into southern Kentucky certainly gets your attention in this area. However, in a few months shy of 27 years of tracking this stuff specifically here, I can't remember a time where we've had a trough this sharp situated this far south, and we not get major convection near the Gulf Coast. And with how negatively tilted this trough is, any convection down south would likely outrun the eastward progress of the convection farther north. I could quite easily see this being a case where areas from Montgomery or Clanton northward eventually get cut off from the main severe weather risk. It almost always happens with a trough as sharp as this one is, as negatively tilted as this one is, positioned as far south as this one will be. We still have to watch things though. I don't think Dixie, overall, escapes a severe weather risk this week.

 

[MichelleH]

BMX has a "2" for tornadoes for Thursday as of this morning. From this morning's AFD:

Severe Weather (Thu afternoon - Thu night): With expectation of a
relatively dynamic system moving northeastward across the region and
better model consistency suggesting so, forecast confidence on
severe weather is increasing. The strengthening low-level jet
wrapping into the occluding & deepening low pressure system not
only suggests low-level & deep-layer shear values will increase
with time, but also a warm sector with 250-500 J/kg MLCAPE to
spread farther north toward the TN Valley. With the overlap of
buoyancy/increasing dewpoints and strengthening presence of
kinematic fields/curved hodographs (300-400 m2/s2 0-1 km SRH) Thu
evening and into Thu night, the threat for damaging winds and
tornadoes is becoming more apparent. Though I still struggle to
visualize overall convective evolution & behavior Thu evening,
the tilt/orientation of the system also suggests decent 0-3 & 0-6
km shear vector crossover which promotes line-embedded supercells
and bowing segments as the mixed convective complex advances
northeast across Central Alabama. The HWO will reflect latest
trends and forecast thinking of the severe weather threat on
Thursday.


And from SPC's Day 4 Outlook:

An upper-level low is forecast to move northeastward across the
southern Plains on Thursday as an associated cold front advances
eastward into the lower Mississippi Valley. Moisture advection
appears likely to continue ahead of the front across the central
Gulf Coast states where surface dewpoints should be in the 60s F.
Thunderstorms may develop during the day along the front with
additional convection forming further east across the moist sector.
Model forecasts suggest that a low-level jet will increase in
strength, moving north-northeastward across Alabama during the late
afternoon. Convective development may be favored on the nose of the
low-level jet during the late afternoon and early evening.
Additional storms may develop further to the west across the lower
Mississippi Valley. Low-level and deep-layer shear profiles should
be favorable for severe storms across those two areas. The main
threats would be for tornadoes and wind damage. At this point, there
is some uncertainty concerning how far the quality moisture can
advect northward. For this outlook, have drawn the 15 percent
contour across central Alabama, where there appears to be a good
chance surface dewpoints will reach the lower to mid 60s F.

 

[Lori]

Seeing even the GFS, with the southernmost surface low track, get 60 dewpoints up into southern Kentucky certainly gets your attention in this area. However, in a few months shy of 27 years of tracking this stuff specifically here, I can't remember a time where we've had a trough this sharp situated this far south, and we not get major convection near the Gulf Coast. And with how negatively tilted this trough is, any convection down south would likely outrun the eastward progress of the convection farther north. I could quite easily see this being a case where areas from Montgomery or Clanton northward eventually get cut off from the main severe weather risk. It almost always happens with a trough as sharp as this one is, as negatively tilted as this one is, positioned as far south as this one will be. We still have to watch things though. I don't think Dixie, overall, escapes a severe weather risk this week.

Thanks Fred!!