CUmet

Everything that I thought I knew about violent tornadoes and death tolls has gone out the window this spring. It's been a long time since we've seen these kinds of death tolls, and I (like many others I imagine) was lulled into this idea that we wouldn't see this again. I've heard various sentiments in the past few weeks to the effect of "if you get a violent tornado going through a densely populated area, deaths are inevitable". While that may have some truth to it, I cannot help but feel that this is an insufficient answer. Like you Josh, I'm wondering how this happened, given how many violent tornadoes have rolled through significant population centers in the past few decades. Why weren't the Moore-OKC (1999) or Pleasant Grove (1998) tornadoes more deadly, for example?

This was easily the most intense outbreak I have ever followed in my dozen or so years of outbreak-following experience. The staggering death toll and the magnitude of the devastation have been tragic and unexpected even to me. Although I suspected an event of historic magnitude would occur, this event has surpassed all of my expectations and deepest fears. If someone said yesterday that the death toll would be into the hundreds, even I (being one of the more bullish on this event) would've thought it was total alarmist hogwash. Shows you how naive I was... It was pretty apparent to me early on that either Tuesday or Wednesday would be the biggest day. The timing of the subtle waves embedded within the larger-scale trough determined which of these days would be bigger. I think it was on Monday when it really became apparent that although parameters were quite impressive on Tuesday aftn/evening, the main wave would eject out on Wednesday...sparking off a new secondary low. The screaming mid-upper level jet associated with the large-scale synoptic trough and the quality of the moisture over such a large area screamed "historic outbreak" to me. The one remaining question was the morning convection and how much that would hamper instability in the warm sector. It did actually accomplish this to some extent...much of the area north of the SE 1/3 of TN were largely spared from this outbreak. The RUC runs from the overnight hours before the event had no precip over this region, and had this verified in reality, the outbreak would've been incomprehensible. I have followed many big tornado outbreaks over the past dozen years, and this was the first one in which I was genuinely fearful in the day or two preceding the event. This one really scared me. I didn't say that directly in any of my posts, as I'd much rather stick to the cold hard analysis of the event and leave much of the drama and emotional side out of it. Probably some of you were able to read between the lines anyways. But in any case, starting on Monday and going into Tuesday evening/overnight, this felt different from the other outbreaks.

Although the death toll will undoubtedly rise, I find the report of "hundreds of casualties" really hard to believe. I mean, we haven't had a 100+ fatality tornado in decades, and that was during the pre-tornado siren days.

The cells firing along the prefrontal confluence line in central MS are likely to emerge as the main show over the next several hours. They are moving into a very unstable environment, and have access to the backed surface wind field.

Cell currently WNW of Greenwood, MS is probably our first long-track tornado threat from the new cluster of development. Rotation appears to be tightening quickly. Greenwood sfc ob is at 81/72 right now, and this warm/moist air is surging northward in the wake of prior convection.

lol it just had to be Broyles. Not criticizing by any means, as I would've done the same thing.

Just woke up...unfortunate to hear some of the damage reports coming in from the overnight activity. There is tons of clearing south of that cluster in northern MS. The HRRR and RUC both have that cluster shifting quickly northeastward and weakening, with the atmosphere quickly destabilizing in its wake. Some of the forecast soundings later this afternoon across MS/AL/S TN are incredible and some of the most impressive I've ever seen from this part of the country...or anywhere else for that matter. My first thoughts this morning are that this is going to live up to the hype.

Completely agree that the middle road is probably the best option given each of the model biases. The latest HRRR run that goes out to 17z probably represents my own thoughts pretty well.

The hi-res models are all over the map right now, with the HRRR and SPC-WRF showing considerable morning convection pretty far south, while the RUC has nothing.

A few honest points, as I do respect your opinion quite a bit. I don't think you can say that yesterday and today underperformed (unless you were expecting a lot more). Yesterday ended up being a pretty decent outbreak with quite a few tornado reports, and today as well. The weakness of today's event (the weaker low-level wind field) was highlighted indirectly earlier, when it was stated that the timing of the trough was a bit slow, resulting in a weaker low-level response. Regardless, I am not a fan at all of the philosophy "the first day ended up underperforming, therefore the second day is more likely to underperform as well". Personally, I tend to treat every day as an independent event, because that's what they really are for the most part w.r.t severe weather. New geographic area, new instability/shear parameters, new storm mode questions, new morning precip issues, etc. I don't think we'll have a problem of too many storms interfering with each other tomorrow. Unlike today, there is a clear focus for convective initiation, and given that the deep-layer shear vectors are perpendicular to the boundary (think April 15-16), it will ensure a sustained discrete supercell mode. There are questions regarding the extent of morning convection and its impact on the warm sector instability, but even the latest NAM run as Tony said is destablizing things very quickly following the passage of the first cluster. If there isn't a major tornado outbreak tomorrow, the morning convection is most likely going to be responsible. Given the extreme rarity of seeing a strong mid-level 100 kt jet streak punching through a moist, unstable warm sector, with cyclogenesis ramping up the low-level wind fields and skyrocketing the helicities...the strong language used by me and many other mets regarding this event has been and is 100% justified. I try my best not to hype things up, and I'm brutally honest when I say I don't like a particular setup for reasons x,y,z. On the other hand, I know potential when I see it, and I have to be honest when I say that this might be the best outbreak setup I've seen in the dozen or so years I've been following severe weather. Whether it actually verifies that way or not, we'll just have to see...

Although RUC isn't usually the best performer with regard to morning MCS events, it is noteworthy that it shows absolutely zero morning precip occurring over the current MDT risk area, for the exception of the far northwestern sliver. No hint whatsoever of the morning convection shown by the NAM/GFS. It'll be interesting to see whether the HRRR shows something similar as well once we get into its range.

The number of violent F4/F5 tornadoes in the Super Outbreak (as opposed to the overall number) is probably the most anomalous aspect of it to me. If you consider the major outbreaks of the past 20 years or so and compare the number of violent tornadoes, they don't even come anywhere close to the Super Outbreak.

From my perspective, I think it's very unlikely that this event will match the Super Outbreak, perhaps even if you count today's and tomorrow's tornadoes as part of the same outbreak. That was an incredible event on many levels, and it's extremely difficult to get amazing parameters over such a large area. With that said, there have been occasional attempts over the years at comparing some upcoming event to the Super Outbreak, and I've laughed off or scoffed at every single one. This time feels a little different.

I agree 100%. The morning convection is the one thing that can go "wrong", but like you said many times the storms do move well out ahead of the warm sector allowing destablization to occur behind it. This seems especially likely in this case due to the fast storm motions. There may even be some subsidence behind the lead shortwave that could facilitate this as well.

A somewhat disturbing trend that I've noticed in following the last 24 hours worth of model runs is that the GFS, ECMWF, and UKMET have all trended stronger with the second low on Wednesday. The NAM has always had a strong second low. In this particular case, it will be important for the intensification of this low to materialize in order to back the surface winds. This seems pretty likely in this particular case given the progression of the second shortwave, but those who have more expertise with the synoptic aspect can probably comment further on this.

I don't think we disagree very much at all. Honestly, I think all three days will be significant tornado outbreaks. I think Tuesday and Wednesday both have a higher ceiling than Monday. Tuesday probably has the highest "bust" potential due to the slightly-off timing of the second disturbance.

I think the spinoff is fine, otherwise it's going to be one massive superthread especially given the magnitude of the event. We can keep this thread around for general thoughts on the Tuesday-Wednesday period. As we get closer, we can split off another thread for Tuesday and Wednesday each as necessary.

I was actually thinking of keeping this thread for Tuesday-Wednesday, and spinning off a new thread for the Monday event since the Tues-Wed event looks like the main show. The discussion in this thread has been mostly about the Tue-Wed threat thus far too. Honestly, we'll probably end up having 3 separate threads for the 3 different days, given the likely magnitude of the event as a whole, so should we just start that up now?

I realize that this is the unreliable NAM at 78-84 hours out, but for Wednesday it has a 100 kt isotach at 500 mb overlapping the warm sector. I honestly cannot recall seeing that ever happening in any model run of a potential severe weather event over at least the past half-decade, and there have only been a select few severe events in the past that have featured this (Palm Sunday 1965, Super Outbreak 1974 come to mind). This is not to say that I *expect* an event of this magnitude, but there is a massive amount of potential here.

This has a legitimate shot at being the outbreak of the year, and this is not hyperbole by any means. At least the areal coverage of this event will be much larger than the April 15-16 event, and frankly all of the parameters are more impressive all across the board. There's still some time for some details to change, but the models have been amazingly consistent over the past several days in showing the same general synoptic solution.

This is a dangerous scenario the models are suggesting, as this would probably result in a massive tornado outbreak on either/both April 26 or 27. At this point, still being 4-5 days out, this is one of the most impressive synoptic-scale setups for a tornado outbreak that I can remember in recent times.

Operational and ensemble runs from the GFS and ECMWF have consistently indicated a huge longwave trough moving eastward over the Central U.S. during this time frame. Embedded within this large-scale trough will likely be at least a couple vort maxes, one of which looks likely to eject out into the Plains on April 25, and another right on its heels on April 26-27. Specifics are lacking at the moment since we're still 6+ days away, but the large-scale pattern is highly suggestive of a major severe weather/tornado outbreak occurring on at least one of these days, if not multiple days.