OceanStWx

The hours covering 21z/27 - 00z/28 will include the tornado that hit both Tuscaloosa and Birmingham.

For what specifically? The extreme part of the outbreak lasted well over 8 hours.

CNN had one of their field reporters bring up a great point that adds to the complexity of the damage assessments. Some of these piles of rubble, did not originate from the nearest foundation. Some of these were just deposited there, and it takes time to figure out whether it came from there or somewhere else.

You know what struck me (besides the obvious devastation down the middle) were the strips of damage that most likely were associated with vorticies rotating around the main funnel. We know these were occurring from the various videos out there, and the damage seems to confirm that these were also very strong, to no ones surprise.

Being a student of Fujita, I would say he's got a pretty sound base of knowledge on the subject. I remember his assessment while in Atlanta as he viewed damage in Yazoo City was excellent.

Couldn't agree more, considering how rare an event they are in the first place having those ingredients come together covering that great a distance is awe inspiring.

Thank you for clearing up my error, I knew that didn't sound right as I was typing it. The fact remains that the wind speeds are determined from damage, and the damage that occurred in 1974 is what is being compared to this event. In fact one could argue that poorly built structures 36 years ago might have been rated lower with the current EF scale not higher. I also apologize if this discussion no longer belongs in this thread, it seems to have taken quite the tailspin since I left work.

I would tend to agree that it lifted east of Birmingham and put down a new one before hitting Rome, GA. However, the damage assessment could ultimately prove me wrong.

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.

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.).

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.

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).

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.

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).

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.

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.

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

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.

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.

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.

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

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