2020-04-12 EVENT: TX/AR/LA/TN/KY/MS/AL/GA/FL

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Steve Carmel

Guest
Mar 3, 2012
3
2
1
CNN a bit critical on damage ratings, with before and after imagery.


IMHO from some of the damage I have seen reported - I had a hard time not believing some of the damage reached EF-5 levels, with well constructed homes totally scraped from their foundations.

Awaiting the final results - widths remind me of Hallam, NE tornado from May 22nd, 2004.
 

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rdale

EF5
Mar 1, 2004
7,213
773
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Lansing, MI
skywatch.org
CNN a bit critical on damage ratings, with before and after imagery.
Critical in what way? Maybe they edited but it just appears they are explaining how they are ranked.

IMHO from some of the damage I have seen reported - I had a hard time not believing some of the damage reached EF-5 levels, with well constructed homes totally scraped from their foundations.
A home "slab swept clean" starts at 165mph.
 
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Jeff Duda

Resident meteorological expert
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Oct 7, 2008
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Couple of points here:

The big one is that the most recent official PNS from Jackson, which was released only last night, remains incomplete for the big tornado tracks. (National Weather Service Text Product Display ...probably not a permalink). That means things could change, including the final rating.

I am confident the NWS Jackson WFO will perform a sufficiently detailed damage survey. It is their job. And since the tornado was known to be significant at the time, a Quick Response Team was probably summoned and will help perform a more scrutinized-than-average survey. That is probably one reason (other than the amount of ground to cover given the length of the track) the survey is taking a long time.

The second big point to consider is that EF-scale rating is based on estimated wind speeds based on damage, and for each DI that is inspected, the DOD has a range of possible values that are dependent on quality of construction. In any rural areas, but especially those in the deep South, where money probably isn't great and things were built a long time ago, construction quality is likely to be pretty poor for most DIs. So even if a DI received the maximum DOD, poor construction quality would force the assessor to select the low end of the range of wind speeds to assign to that damage. It is not easy nor simple to distinguish between EF4 and EF5 damage in the modern era using traditional DIs like single family detached homes (a staple of the old Fujita scale). Provided you don't see something truly extreme, like craters or entire swaths of forest swept clean (not talking about a massive blowdown of trees, but the trunks carried away from their original location, too), you're not going to be able to declare EF5 damage from a broad, cursory examination of some damage from afar. You need to examine details like quality of construction, which takes a trained eye to spot.

Also keep in mind that many tornadoes probably end up being recorded as lesser rated than they could have been because of a dearth of DIs. If a tornado containing 300 mph winds goes through an open field and never impacts any robust structures directly, it will go down as something less than EF5, including EFU. So not every tornado even *has* the potential to be rated EF4/5 because there just aren't DIs to impact.
 

Joey Prom

EF1
Feb 11, 2020
68
23
6
St. Paul, Minnesota
A person on the Discord server posted the following comments, just wondering what y'all's thinking on this is:

"For Easter Sunday, there's still just one burning question to me in which I'd love to hear opinions on. Despite this being a very massive tornado outbreak with more and more tornadoes being reported even still, the one part that did NOT make sense to me was Southern AL having very few tornadoes and a very mitigated threat while being surrounded with strong tornadoes. S AL had a lot of surface heating in the warm sector after the midday mess of storms went through, and if North-Central AL and S GA didn't have these problems with reheating, It doesn't make sense that S AL would've had them. When the two strong supercells that put down the Bassfield tornado family first came out of the elevated LA convection, it was assumed that these supercells would continue to track deep through AL in a very healthy warm sector. The first cell, however, inexplicably died as it got close to the MS/AL border. The cell, when it died, accelerated and turned VERY hard left, going almost due north up the state line. The second, trail cell that also was producing tornadoes did almost the exact same thing at the exact same location. The third supercell in the line, which never quite produced tornadoes iirc but was a healthy looking supercell that looked to become dominant, also behaved very similarly, and again in almost the exact same location. The HRRR nailed the development of the first two supercells, but did not anticipate their death. The burning question for me is: why did these supercells die in what looked to be an extremely healthy environment? Does the rapid left turn indicate capping problems and them becoming elevated as they got to the border, perhaps because the cap hadn't eroded enough? Or is there something else at play here?(edited)

In addition, new elevated development in the LA panhandle, further south than the 2x EF-4 family that started just west of the same location, was fully expected to become supercellular with time as they went more surface based in SE MS. This Cellular development, however, never quite went surface based, and it appeared to form into a messy squall before it could become fully surface based. This squall didn't become organized in a QLCS mode until it reached Georgia, with S AL getting a grungy, messy squall that produced nothing but severe winds. As soon as this squall got past AL, it became more QLCS in nature and produced numerous tornadoes, including eventually leading to the stronger ones that impacted Southern SC at about 11Z (two of which got EF-3 ratings, iirc). I've heard a few theories about why this has taken place, but I'd like to get more opinions from people who know more about this event than I do. The theories I've heard thus far: 1) Surface heating wasn't as great in AL, and the cap was still in place; as a result only more linear storm modes were sustainable in that area 2) Winds veered unexpectedly early, killing surface convergence in S AL. Even if this was the case, why'd the storms suddenly become more tornadic once they reached GA? The shear profiles in AL were still off the charts during the event. 3) The elevated convection in the LA panhandle was growing upscale before it could become surface based, and by that time needed way more time to organize and mature before being able to produce tornadoes. I would favor this theory being that it most closely resembles what I saw on radar during the event, but it doesn't explain the abrupt death of the first supercell family. 4) The shear in S AL was so great that it tore apart the updrafts of any supercells in the area. This could make sense, but wouldn't deeply established supercells be able to harness that energy anyways?

I'm hoping that some of you have more answers than I do. It's certainly an interesting case study given the ridiculous parameters in place in S AL during the event."
 
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Sam Soud

Enthusiast
Mar 30, 2020
5
2
1
Jacksonville, FL
A person on the Discord server posted the following comments, just wondering what y'all's thinking on this is:

"For Easter Sunday, there's still just one burning question to me in which I'd love to hear opinions on. Despite this being a very massive tornado outbreak with more and more tornadoes being reported even still, the one part that did NOT make sense to me was Southern AL having very few tornadoes and a very mitigated threat while being surrounded with strong tornadoes. S AL had a lot of surface heating in the warm sector after the midday mess of storms went through, and if North-Central AL and S GA didn't have these problems with reheating, It doesn't make sense that S AL would've had them. When the two strong supercells that put down the Bassfield tornado family first came out of the elevated LA convection, it was assumed that these supercells would continue to track deep through AL in a very healthy warm sector. The first cell, however, inexplicably died as it got close to the MS/AL border. The cell, when it died, accelerated and turned VERY hard left, going almost due north up the state line. The second, trail cell that also was producing tornadoes did almost the exact same thing at the exact same location. The third supercell in the line, which never quite produced tornadoes iirc but was a healthy looking supercell that looked to become dominant, also behaved very similarly, and again in almost the exact same location. The HRRR nailed the development of the first two supercells, but did not anticipate their death. The burning question for me is: why did these supercells die in what looked to be an extremely healthy environment? Does the rapid left turn indicate capping problems and them becoming elevated as they got to the border, perhaps because the cap hadn't eroded enough? Or is there something else at play here?(edited)

In addition, new elevated development in the LA panhandle, further south than the 2x EF-4 family that started just west of the same location, was fully expected to become supercellular with time as they went more surface based in SE MS. This Cellular development, however, never quite went surface based, and it appeared to form into a messy squall before it could become fully surface based. This squall didn't become organized in a QLCS mode until it reached Georgia, with S AL getting a grungy, messy squall that produced nothing but severe winds. As soon as this squall got past AL, it became more QLCS in nature and produced numerous tornadoes, including eventually leading to the stronger ones that impacted Southern SC at about 11Z (two of which got EF-3 ratings, iirc). I've heard a few theories about why this has taken place, but I'd like to get more opinions from people who know more about this event than I do. The theories I've heard thus far: 1) Surface heating wasn't as great in AL, and the cap was still in place; as a result only more linear storm modes were sustainable in that area 2) Winds veered unexpectedly early, killing surface convergence in S AL. Even if this was the case, why'd the storms suddenly become more tornadic once they reached GA? The shear profiles in AL were still off the charts during the event. 3) The elevated convection in the LA panhandle was growing upscale before it could become surface based, and by that time needed way more time to organize and mature before being able to produce tornadoes. I would favor this theory being that it most closely resembles what I saw on radar during the event, but it doesn't explain the abrupt death of the first supercell family. 4) The shear in S AL was so great that it tore apart the updrafts of any supercells in the area. This could make sense, but wouldn't deeply established supercells be able to harness that energy anyways?

I'm hoping that some of you have more answers than I do. It's certainly an interesting case study given the ridiculous parameters in place in S AL during the event."
This is a post I made in the chaser discussion over on the discord channel. I certainly seem to not have all the answers to this even still. One thing that was also brought to my attention was the 500mb height falls in the area, and that the 576dm contour commonly indicates the southern bounds of a dixie event. That being said, my understanding of heights is basically zero, so if somebody has a basic answer that would be appreciated.
 
Jun 1, 2008
530
468
11
Chattanooga, TN
www.linkedin.com
The Davies write-up is excellent as usual. I did not actively chase this night time tornado in Chattanooga, though it was about 1.25 miles to my northwest. During the day, might have been worth a look. At night, raining, Dixie, nah. At any rate, count KCHA with that nw GA/se TN sounding.

My notes: 11:03 pm severe t-storm warning Hamilton Co. I'm still hoping rotation dies down, but it increases coming toward us. 11:17 pm tornado warning radar indicated, my location East Brainerd. Take shelter with helmets. Wind is loud behind weather radio walkie-talkie. Try to reload radar on phone, no Internet. Power goes out, likely as tornado crosses the main road (to our west) from which our power comes. 11:24? Tornado Emergency Collegedale and Ootelwah - just to my northeast. Winds actually diminish here. No damage at our house.

Two days later I venture out. Lovely orange (in fall) tree is decimated over East Brainerd EB Rd. Bones is a pile of twisted rubble, but not blown away – though a menu is in Cleveland, Tenn. Several power trucks are working the EB line - rebuilding poles and hanging lines. Episcopal Crucifix stands proudly and defiantly! Small church on Shallowford Rd roof pancaked on downstairs. Shalloword trees are stripped bare. Power lines droop over Banks Rd. Help family friends clean-up, document small and large debris. Some 2x4s in the next block. Their block is mainly small pieces of roof, insulation stuck to sides, and some glass in the yard. Screwdriver is from next block neighbor’s tool box. Next ridge (roads closed) is damaged houses as far as the eye can see. Jenkins Rd feels like a prairie country road where police block it; however, I forgot it was a tree-lined residential area.

Four days later we got power and Internet back. This tornado is personal. Several friends lost homes. Many more friends had minor damage. Thankfully nobody I know was hurt. Still I'm heartbroken for the family of the 4-year old who succumbed to injuries in the hospital.

Given this was never an attempted chase will post in Event, rather than start Reports.