Chreeyiss

I believe a PDS watch is issued for 80% and up, but I’m guessing they didn’t go that high because of the potential for these storms to merge upscale somewhat quickly. I bet they’d have gone PDS if it looked like this were going to stay discrete for longer.

11 minutes ago, TheSuckZone said:

I'd agree with that. I'm also not a fan of T-Storm watches with "couple tornadoes possible". Has this always been a deal? I don't remember T-Storm watches ever being like that and I don't understand what the harm is in just making it a Tornado Watch.

I would guess it gives the wrong idea to the public. The subset of people who actually recognize the difference between a svr watch and a tor watch, but aren’t invested enough to frequently check in are probably inclined to view it as a “cry wolf” incident if a tornado watch is issued for a risk that’s so low that only 1 or 2 tornadoes occurs in an entire watch box. Most people in this group are only aware of what’s happening in their city or news coverage that cuts into their tv shows.

Not that it really matters this far out, but despite the relative consistency in the gfs (cmc and euro have been all over the place), I see some things that are far from being nailed down:

- Timing: looks like overnight Tue-Wed (though gfs tends to be too progressive, might this eventually turn into a Wed event for the plains?)

- 500mb pattern: Will there be a northern lobe and associated surface low in Kansas and Nebraska, as shown on some runs, or will the southern lobe in NW Texas remain dominant?

- Will the low level jet sync sufficiently with the upper levels and create a favorable shear profile, and if so, where? (imagine this is a function of the 2 points above)

First thing that comes to mind for me looking over these runs, at least for Texas and Oklahoma, is an overnight MCS. If shear and instability are sufficient, maybe there would be an embedded supercell/tornado risk. 0z GFS run doesnt really maximize either of these though. Of course, all of this is speculation on my part for entertainment purposes and an attempt to see if I've learned anything at all over time regarding pattern recognition. It also makes the lofty assumption that the GFS is onto something to begin with.  Guess we'll see. 

7 minutes ago, WxSynopsisDavid said:

Disagree with temps. Your assumption applies to a high cape/low shear environment. You don’t need temps higher than the 60’s with high shear/low cape setups.

I’m not broad brushing that as rule in general, but for this particular setup, from what I’ve seen on the models, the cap looks like it prevents surface based instability from being fully utilized unless temps exceed about 66 degrees. I might be wrong, but it looks like that’s the main differentiator between central Texas and points further north in DFW where the shear profiles are at least as extreme. If I’m wrong on this though, I would love to learn more.

Looks like Tuesday has taken the title of biggest day instead of Monday, but Monday has very high potential too. The SRH values in north and central Texas Monday afternoon are absurd. Like 500-750m2/s2. However, if temps stay mid 60s or below during the afternoon across this area, the full potential probably won’t be realized

37 minutes ago, CheeselandSkies said:

The modeled environments looked pretty ominous at one point (at least on the GFS, and it was pretty consistent with that for quite a few runs) but have downtrended a bit as the event gets closer and I wouldn't say support a high risk type setup at this juncture. Not to say they couldn't trend back in the other direction.

Agreed, there doesn't seem to be as much of an overlap between that extremely favorable shear and sufficient instability on these more recent runs. Looks more like a broad brushed slight with a pocket of enhanced in central Texas to me, if these trends hold. 

6 hours ago, Powerball said:

Lapse rates are looking pretty poor on Monday.

Seems more like a heavy rain vs severe setup.

True, I guess we will see. The shear profiles look very favorable across the eastern half of Texas, and the SPC notes this in their convective outlook as well. GFS does sometimes underestimate instability and lapse rates on these early season events, but I wouldn't be surprised the event busts up here for the reason you mentioned. CLL and south may end up being the bullseye where thermos are better.

Won’t sleep on tomorrow, but Monday is continuing to look like the main event.

Today has met my expectations here in Dallas proper. It’s hailed 3 times here in the last hour, though fairly small. Got some good bursts of rain and a couple nice SLCs to look at. Maybe more on the way judging by radar, though I imagine these latest storms have probably tapped most of the good conditions over me.

21 minutes ago, Powerball said:

Yep.

It's looking like it might be a miss here, yet again.

Unless you live along or west of 35, you might luck out. Lots of storms firing in the metro now

First attempts at initiation look to be appearing south of Arlington

2 hours ago, Powerball said:

Maybe, depending on how the radar looks this evening.

Hi-Res models are now back to holding off intitiation until just east of DFW.

*sigh*

True the HRRR is back east, but its soundings show >1500j/kg in an uncapped atmosphere along and east of 35 by 5pm. Not going to take much to get storms to initiate west of where it currently depicts. 
 

NAM, ARW, and ARW2 are closer to 35 with initiation.

23 minutes ago, DanLarsen34 said:

 

I’ve seen wxtwitter abuzz with comments along the lines of “who cares what EF rating the tornado gets when there are lives lost and damage done?”

I understand that thought, as there are a lot of people who seem to care only about the damage rating, but the two sentiments aren’t mutually exclusive, as many others have pointed out. What you posted above is why we should still care about the integrity of the EF rating. 
 

Quick googling shows that there have been 631 F/EF 4+’s documented from 1950 to 2017. With an average of 1200 tornadoes per year, and an ef4+ rate of 20% according to the study, that means if we could derive tornado intensity from measures other than just damage, it would only take about 3 years to document the same number of ef4+ tornadoes that we have accumulated over the span of 67 years. 
 

Findings like this demonstrate the impacts of the limitations of the EF scale, and the truncation of a given tornado sample size to less than 5% of what it should be must have some pretty significant impacts on the ability to derive trends and make predictions. 

48 minutes ago, Moderately Unstable said:

Hm. Well, it's splitting hairs to some degree I think (10mph from EF-5); very similar overall "thinking" to Bassfield, which as many recall we all were discussing an EF-5 rating as well. 

I actually have a counter-thought with respect to Tim Marshall. What if he gets called in when the NWS team *doesn't* have the damage indicators it needs to make its own assessment and needs an outside expert to review things that have been destroyed and basically assign a damage indicator rating on the fly? Many have pointed out that the structures on path wouldn't be able to generate an EF-5 rating. My interpretation when they called in the "experts" was that, they had damage that they were struggling to classify. Otherwise, why bring in said experts? Yes high ratings are important publicly speaking--but they're the sole discretion of the office in the affected CWA.

I also wonder, would those 2011 ratings have changed? Or, were there genuinely different building materials or other factors? I feel like, as much as we are kind of trashing tim (et al) right now, he obviously *is* an expert on tornado intensity. I'd be curious to understand the process Tim himself goes through when he does these evals. Does he incorporate Doppler radar data concurrent to the location he's evaluating? How does he and the NWS evaluate something that is "beyond destroyed"? What I mean is, I picture Tim coming in to answer the question, "this well built home was slabbed but xyz was not built correctly so there's XYZ ambiguity, is there anything you can see in the wreckage that looks like it would take a higher wind speed to be able to do THAT destruction?". One thing I've read about EF-5 damage is that the debris is often "pulverized" into a "fine powder" with "little recognizable from the original structure". Of course if that is the bar, there are EF-5s and F5s that would under our current rating scheme get downgraded.

All this said, my gut instinct is, hard as it is to believe, had Tim and co found some type of incredible damage as it were, they could still have issued an EF-5 rating on path. That's why they call in the experts. Arguably, we probably rated tornadoes overly agressive in the past, as opposed to rating them too-low now. Various numerics during the tornado including vrot had many on Twitter and a couple on here calling it EF-4 strength (while noting, if it were a bit closer to higher STPs and more population it'd be a 5). But since it wasn't, technically the radar does kinda track with a very high end 4 ( 30k feet debris loft is significant though--but could also be a function of the strength of the overall supercell's organization, which makes sense for many reasons and is what enabled such a strong tornado in the first place).

 

My final thought is, based on all the above, this would've been a 5 in 2011, 2007, before the EF scale (etc). The reason it isn't now feels like it is less to do with a change in *damage*, instead, we have a much better understanding of what *wind speed* is required to *produce* given damage (and for what duration and at what angle that wind must impinge on the structure or object in question). We understand now that things like forward speed, and angle of approach, can influence damage to structures. Therefore, I'd argue that the *windspeed* estimate is probably right, and the scale itself might need to be tweaked. We all know, EF5 means "incredible" and "catastrophic" damage. This IS that damage. It is just that. Catastrophic. And not to split hairs but it's more than "Devastating". I'd argue, devastating means everything is destroyed but it doesn't look like entire towns were model cities that had been carelessly thrown off the end of a high table by a child. Particularly what I saw coming out of Bremen. 

I therefore suggest we reconsider our rating criteria, by reducing the wind speed threshold required for EF5 ratings. The point of the rating is to inform the severity. This is top tier severity, it should have a top tier rating. If 190 mph winds do this damage, 190 should be a 5. 

Obviously you’re the met, so your opinion is much better informed than mine, but it seems to me that if if our intensity scale is to continue relying heavily on damage produced over other indicators, that the scale needs to be updated with more non-urban damage indicators for EF4+ tornadoes, rather than a downward adjustment of winds in the ef5 category. In concept, it doesn’t make a whole lot of sense that a tornado’s intensity is only as strong as the building it hits (or doesn’t hit) but even with improvements in technology, it’s still the best we’ve got. Tornadoes predominantly hit rural or even unpopulated areas, and if tornado intensity is going to continue to be evaluated by this methodology, I would think the next logical step in improving the scale would be to accommodate that fact better.
 

The NIST slideshow about Joplin that was posted above makes note of the large amount of subjectivity that comes into play when evaluating unconventional damage indicators due to construction methods that can’t generate an ef5 rating. I’m sure Tim’s statement was made on the fly, but using two tornadoes that were clearly well above the F5 threshold as the benchmark for 201mph winds doesn’t seem like a fair comparison to me.

If I had any say in the matter, I personally would only advocate for lowering the wind threshold if structural engineering studies determined that what is generally considered ef5 damage was produced at lower wind speeds, or if we were to lower the standard for what is considered ef5 damage. 
 

Let me know if my line of thinking here isn’t correct.

Like many of you, I am confused by Tim’s statement. Our benchmark for ef5 now is one tornado measured at over 300mph, and another tornado that imparted f5 impacts on a given location for longer than practically any other on record?

If that’s the case, why would we even consider 201 mph the threshold, and not  something higher like 250 or 300?

edit:typo

Ah, missed that. Thanks for the clarification.

31 minutes ago, cheese007 said:

As a counterpoint to the previous tweet. Would not be shocked if EF-4 is the final rating

Surprising to me that not even those houses in that lakefront community (I think near Earlington?) count. I guess building codes aren’t sufficient even in the wealthier areas.

5 minutes ago, cheese007 said:

Looks like the tri-state record may stand after all

It can but honestly it probably shouldn’t. Each of these events are likely similar in that they are probably not continuous.

4 minutes ago, cheese007 said:

 

That’s some crazy damage but I don’t buy the pavement scouring claim based on the photos provided. If they’re talking about the picture with the driveway, those appear to be tire tracks to me. They follow the path of the driveway exactly.

3 minutes ago, andyhb said:

In excess of 170 mph (EF4+), that's my only estimate for now.

I know you’re stating that as the lower bound, but it’s hard for me to imagine the survey will conclude anywhere near that low, given the insane velocity bins on radar last night. This will be a great case study on how g2g values translate to damage surveys, or don’t.

Looks to have weakened a bit on approach to Dawson Springs, but it is by no means weak and definitely still on the ground. Not good.

It seems to be maxing out the velocity scale in both directions now on RadarScope. This couplet is absurd.

I think something is up with the spc site. I checked it earlier this morning and connective outlooks were starting day 1 as Jan 20th

Unexpected tornado warning in Louisiana, even a brief tds

20 minutes ago, cstrunk said:

Yeah, all of the clouds are going to put a damper on things, IMO. Already seeing junk showers from I-35 east. Need that to move out and see some sun ASAP.

I don’t think it will be much of an issue. Instability picks up drastically as the dryline approaches this afternoon. That doesn’t mean storms are guaranteed to fire, but any issues won’t be instability driven.