OceanStWx

This is not a met perspective.

F5 in the 1970s is to '_____' on the Enhanced Fujita scale? How much knowledge did those folks surveying damage in 1974 have compared to what they have now? In every industry, we are light years ahead of where we were in 1974. To say an F5 tornado in the 70s has any relevance to how a tornado is rated today (if comparing intensities), is short-sighted - and irrelevant.

I would think the met point of view here would actually argue opposite your point.

Unless you can run a GRLevelx scan of the 74 outbreak using today's Doppler's and computer technology, and THEN go survey the damage with homes built exactly the same, from the same building materials...Why even bring up the Fujita intensity rating of something that happened over 35 years ago and relate it to how well the two systems stack-rank met-wise against one another?

They are the same, the Fujita scale was always a damage scale not a wind scale. The damage is still the same, we've just realized the winds need not be 300 mph to wipe a foundation clean.

I'm sure some of the people that died while hunkered down would disagree.

Yeah, it's not a great policy for the general public on the whole (especially in highly populated areas), but if you're weather savvy and can evacuate, why not?

Weather savvy is one thing, but the vast majority of the public cannot be included in that category. A number of good reasons for not advocated mass evacuations of towns/cities have been listed already (obstructions to visibility, unpredictability of short term storm evolutions, nighttime tornadoes, traffic, etc.).

Well, I hope you're correct. I'd like to get a decent handle on the survival rate but the 50% was an approximate number I got from a met but that doesn't mean that its necessarily accurate. This is a most important point, though. The survival rate for a violent (EF4+) tornado for people suffering a direct hit and who are sheltering in an interior room on the lowest floor of a standard wood-frame house is really a key point. If it's something like 90%+, then you would be correct in saying that sheltering in place is probably the best thing to tell the population in the path to do. However, if it's more like 60% or less, there is probably something viable that could be done for those in the path...because those types of probabilities are unacceptable.

60% still means you're more likely to survive than not, sheltering in place. While getting in the car still doesn't guarantee you escape the tornado and brings into the equation traffic accidents, etc.

There is too much room for error if you advocate people taking their lives into their own hands on the road.

I was focused heavily on the HSV-area storms yesterday, since I have family there, and I agree to an extent. It appeared to me that the outflow boundary from the MCS may have been draped across the northern row of counties in AL for several hours during the height of the outbreak. One storm in particular, which initially produced the catastrophic Hackleburg/Phil Campbell tornado, seemed to weaken a bit as it moved northeast from that area. Then, it suddenly went crazy upon reaching the Tennessee River, producing the Limestone Co. wedge near Tanner/Athens with visibly much-lower LCL's than the southern storms. For the rest of the afternoon, supercells trained over this general corridor and would each develop strong low-level rotation as they entered the Dectaur/Huntsville metro area.

On the other hand, it still seems that the most prolific, violent tornado-producers were over the open warm sector, south of any clearly-defined boundaries from early convection. So, while I don't believe the MCS is what "made" this outbreak by any means, it may have at minimum not reduced its overall severity.

Virtually speaking, that's where I targeted. I wanted to tuck in behind that morning MCS, so I ended up going with Bear Creek, AL (5 S of Phil Campbell).

All... I'm seeing a lot of slaps with debris surrounding a barren slab in the Cartersville, GA aerial damage surveys...

http://www.myfoxatla...-20110427-am-sd

Can someone with a little more professional POV on EF-intensity/scale give a hypothesis surrounding projected EF-scale for the Cartersville tornado?

This is far worse damage than Murfreesboro, TN (rated EF-4) because JUST the slab remains on many of these homes....

Probably not as wide as Greensburg (maybe so), but definitely the same 'slab only' profile with some of the damage I'm seeing at the above link.

Certainly looks like an EF4 candidate, with even the interior rooms destroyed. But I will reiterate that it is virtually impossible to say with any certainty whether a tornado was EF5 without inspecting construction of the building.

This is a good point. We've seen some instances...I think even in the previous outbreak in AL and NC where homes were severely damaged, but then you had clues to more EF1 damage, like mailboxes which were untouched. Even EF0 tornadoes can overturn cars. It's not just the horizontal velocity of the wind, but you have vertical motions that can combine to overturn a car.

Another surprisingly difficult thing for me, and I'm sure the survey teams will run into this as well, is to go into the damage assessment without preconceived notions. You can't go in thinking EF5 otherwise you will naturally search for indicators that prove it correct, while ignoring those that suggest otherwise. I never ran into tornadoes anywhere close to this intense, but it was often an issue with tornado vs. straight line wind.

These survey teams will have to mentally prepare themselves to be completely objective, despite the devastation laid out before them. I don't envy their position at all, because as much as I would want to be on the team I don't know how I would handle it. The EF2 in Putnam Co., Illinois on 6/5/10 was enough to shake me (being my first significant tornado damage).

Why is that? 167mph on the upper bound falls into the very low-end of EF4.

While that may be true, we're talking 1 mph. And an EF4 rating is not going to be determined based solely off tree damage when there are so many other man made structures impacted.

Once again these large, destructive tornadoes require context. Debarked trees plus a house with partial roof loss does not equal EF3, while a bare slab plus a fully leafed tree does not equal EF5.

I am no expert but I think tress could go up to EF4 damage. I remember seeing tree damage in Andover,KS, Moore, OK, Harper, KS, and Parkersburg Iowa where not only was the trees completely debarked but also shredded down the center. I dont think there were even stumps even remaining. I am seeing trees in Tuscaloosa that are looking comparable. This tornado was at least an EF4 and no less. It is very obvious how violent this tornado was.

Officially this is not the case. The upper bound of damage goes right up to, but not into, EF4 wind speeds. It is impossible to tell beyond 167 mph, how strong the winds were to debark a tree because it could have been large amounts of debris vs. the actual wind speeds throwing the debris that did the damage.

Whats the difference between EF4 and EF5 damage?

In simple terms, the construction of the building in question. EF4 winds devastate structures, EF5 winds devastate well built structures.

Then the live feed over Spaulding Co. GA tseems to suggest at least EF3 in spots, from what my amateur eyes can tell. Definitely the tree damage, though not necessarily in a wide swath or continuous. Some bare concrete slabs, with the adjacent homes suggesting those were either traditional wood-frame or perhaps pre-fab (not trailers.) Also wood-framed houses reduced to rubble with piles of lumber and siding blown across the road.

The most difficult questions will come when going from EF4 to EF5, and will likely take more than just today to determine the answers. A single family home can be reduced to a bare slab in EF1 winds if the house isn't anchored to the foundation. Experts will need to come in and view construction to determine how well they were built. However there are some clues that can help. For instance, a bare slab next to a tree with a couple branches down, or an intact flag pole can be indicative of poor construction. Whereas, a bare slab with debarked trees and a flag pole bent to the ground can show that it was indeed EF3+.

Not to mention the number and magnitude of the rest of the tornadoes mean these surveys are going to take a while, even though they likely have region and surrounding WFOs assisting.

Just going off things we know for sure at this moment...

Trees debarked with only stumps of largest limbs remaining is EF3 expected damage, but only can be determined up to the highest (167 mph) at that scale. After that it becomes impossible to tell with any certainty how strong the winds were.

Likewise, we know transmission towers outside of Birmingham were taken down. Again this type of damage is consistent with EF3 damage, but once total loss occurs it is impossible to tell if winds were stronger.

As for other structures we've seen, there was that McDonalds in Tuscaloosa that was rendered down to just about nothing but the guts (could even argue completely gone). This damage is consistent with EF3 (or high EF4 if you consider it a total loss), and again higher wind speeds can't be stated with any certainty because the structure is expected to be gone at high EF4.

Easily EF3+, almost definitely EF4, and I personally need some context with what certain structures were before they were reduced to rubble before declaring EF5 for sure.

I typically cringe at those guessing these things prematurely, but I would be very surprised if it's not rated as EF5 based on all available information.

Totally agree, I don't like the premature assessments especially when viewing photos without any sort of perspective. However, like you said there is a lot of information pointing in that direction at this hour.

The earlier "hundred dead in Tuscaloosa" rumor appears to be false. Tusc. mayor just reported 15 dead and more than 100 injured.

On a day like today, 100 casualties can accidentally be relayed as 100 deaths pretty easily.

Also careful with the siren discussion because they are only designed to be outdoor warning systems. Folks in cars, office buildings, homes, etc. need to have some other form of communication to receive warnings effectively. For instance, ABC 33/40 was being simulcast on the radio, especially for those without power for TVs.

Fact of the matter is too many people have already died today. There is a reason we work everyday towards improving both the warning process and the responses they generate.

Roy Oswalt, our beloved pitcher on the Phillies, left the team to go make sure his family is ok. he lives somewhere down south MS/AL... so far, all seems well.. Just goes to show, no one is spared with mother nature...

Now back to this historic outbreak

Could have sworn he had to do this last year on the Yazoo City, MS day.

wow, so close

The type of atmosphere today can be seen with the horizontal funnels rising up the outside of the tornado. Shear/helicity just incredible...

I'm afraid NW of Birmingham is going to end up being much worse than Tuscaloosa. On the level of Greensburg, KS or worse.

It was certainly strengthening on the way from Tuscaloosa to Birmingham, I would say the best couplet was just prior to entering the western Birmingham suburbs.

I want to reiterate that the coverage out of ABC 33/40 today has been outstanding, and their message has probably saved many lives.

I especially like (and appreciate) how Spann reiterated not to trust any storm today. That if any thunder was headed your way to take cover, not just the tornado warned ones.

That and this mornings storms and the damage to the infrastructure may have played a factor in that as well.

Good point, the Winfield, AL NOAA weather radio xmtr has been offline or at least having trouble staying online since this morning. Which of course, is why there is overlap with surrounding xmtrs. Inevitably there will be gaps in coverage though.

Possible EF4-EF5 damage in Tuscaloosa.

Stores are completely gone.

Normally with these early reports I would urge caution with taking them verbatim, but coupled with the radar signatures unfortunately this type of damage is not only possible but probable.

What happened to HTX?

Sorry, I'm at lab right now, kinda out of the loop

Phone line problems knocked radar offline.

WFAA - Saying that the town of Phil Campbell was "wiped out".

Which time though, it got slammed by two clear tornadoes with debris balls visible on radar. Many of these towns are taking their 2nd (3rd even) hits of the day.

This says a lot, from the NWS met who worked the Greensburg tornado.

Mike Umscheid This is the greatest Delta-V I have ever seen on wsr-88d.

I haven't been at it very long, but I know my velocity would max out at 250 gate to gate, and I had 240 for a scan. That statement doesn't surprise me, unfortunately.

Looks like a 2nd rotation west of Tuscaloosa again

Very nice RFD punch it looks like on radar, would not be surprised to see another touchdown.

As for the cell that just went through town, radar velocities are about maxed out. Damage reports are going to be extreme.