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Historic Tornado Outbreak April 27, 2011


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Yeah stellar job by TWC. They acted as a weather channel should act.

Really was surprised by the news channels. Big "F" for them from what I saw at least, but I didn't have them on the whole time of course since TWC was a ton better.

I echo the sentiments about TWC coverage. It was fantastic. I didn't turn it off TWC for almost the entire event which is something I can't say I have done in a long long time. They were at their best when the tornado was coming into north BHM. The calmness and professionalism they showed during that moment was incredible considering they absolutely knew the devastation that was occurring. TWC adding Norcross to the team has also been a plus. I was little surprised when he came on air last night, but it was good to see him on outside of tropical coverage.

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Whats the difference between EF4 and EF5 damage?

Honestly EF3-4 damage actually looks more spectacular at first glance than EF5; you have an actual house or building that you can at least tell was a building but which is utterly flattened. The thing about F5s is that you're left with a foundation slab and the wreckage is 2 miles away.

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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 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.

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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.

Errr, no, you cannot possibly have "EF4" damage to trees from a tornado. The EF scale doesn't allow it.

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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.

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CNN now saying 230+ dead

If true, there is a shot we could over the superoutbreak death toll

Just now on fox they had someone from the SPC on and they were comparing this one with the super outbreak they made a very good point..and that is the warning system, communications, and building codes are so much better today than then that for the death toll to be even in shouting distance of the super outbreak is incredible and speaks volumes.

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I heard mention of G2G velocities 1000 feet off the ground maxing 200 knots on these storms. Anyone know if there is some kind of empirical relationship between that and near surface winds?

The G2G on the tornado just east of Tuscaloosa hit 240 kt, maxing out my color curve on GRLevel2. Never seen anything like it.

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PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE BIRMINGHAM AL 808 AM CDT THU APR 28 2011

...UPDATED FOR JEFFERSON AND TUSCALOOSA COUNTY SURVEYS...

IN REGARDS TO THE JEFFERSON AND TUSCALOOSA COUNTY DAMAGE...SUBJECT MATTER EXPERTS FROM AROUND THE COUNTRY WILL BE ARRIVING TODAY TO ASSIST WITH SURVEYS...AND DAMAGE RATINGS WILL BE PROVIDED AFTER A THOROUGH ASSESSMENT IS CONDUCTED.

NATIONAL WEATHER SERVICE METEOROLOGISTS TODAY WILL BEGIN THE TASK OF ASSESSING THE DAMAGE FROM A TRAGICALLY HISTORIC DAY OF TORNADIC ACTIVITY AND SEVERE WEATHER ACROSS CENTRAL ALABAMA. THERE WERE TWO WAVES OF SEVERE WEATHER. THE FIRST MOVED THROUGH DURING THE EARLY MORNING HOURS ACROSS NORTHERN PORTIONS OF CENTRAL ALABAMA PRODUCING DAMAGING STRAIGHT LINE WINDS AND ISOLATED TORNADOES. THE SECOND WAVE INVOLVED NUMEROUS SUPERCELL THUNDERSTORMS AND PRODUCED LONG LIVED... STRONG TO VIOLENT TORNADOES ACROSS THE NORTHERN TWO-THIRDS OF CENTRAL ALABAMA...WITH WIDESPREAD AND CATASTROPHIC DAMAGE IN SEVERAL LOCATIONS.

AT THIS TIME...STORM SURVEYS ARE BEING PLANNED FOR THE FOLLOWING COUNTIES:

TEAM ONE: MARION COUNTY...THREE POSSIBLE TRACKS INCLUDING HACKLEBURG. WALKER COUNTY...THREE POSSIBLE TRACKS INCLUDING CORDOVA.

TEAM TWO: BIBB COUNTY...TWO POSSIBLE TRACKS INCLUDING EOLINE. SUMTER COUNTY...GIEGER.

TEAM THREE: TUSCALOOSA COUNTY...TUSCALOOSA. JEFFERSON COUNTY...PLEASANT GROVE...PRATT CITY.

MEDIA INQUIRIES CAN BE DIRECTED TOWARD WARNING COORDINATION METEOROLOGIST JOHN DE BLOCK AT 205-664-3010...OR METEOROLOGIST IN CHARGE JIM STEFKOVICH AT 205-585-8635.

A MAJOR CONTRIBUTION TO THE SUCCESS OF OUR SEVERE WEATHER WARNING PROGRAM IS THE RECEIPT OF STORM REPORTS FROM ALL OUR CUSTOMERS AND PARTNERS ACROSS CENTRAL ALABAMA. IF YOU WITNESSED OR ARE AWARE OF ANY STORM DAMAGE DUE TO HIGH WINDS OR TORNADOES...PLEASE CONTACT YOUR LOCAL EMERGENCY MANAGEMENT OFFICE...OR CALL OUR STORM REPORTING HOTLINE AT 1-800-856-0758.

$$

JD/02

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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.

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Just now on fox they had someone from the SPC on and they were comparing this one with the super outbreak they made a very good point..and that is the warning system, communications, and building codes are so much better today than then that for the death toll to be even in shouting distance of the super outbreak is incredible and speaks volumes.

I know the suburbs of Cincinnati and Louisville were hit in 1974, and Xenia is hardly a small town, but I'd argue the Superoutbreak did a better job of missing medium and large cities than this outbreak. Also, the population in the South has increased and spread out since then.

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Just now on fox they had someone from the SPC on and they were comparing this one with the super outbreak they made a very good point..and that is the warning system, communications, and building codes are so much better today than then that for the death toll to be even in shouting distance of the super outbreak is incredible and speaks volumes.

Yeah, the fact that some of the most violent and long-lived twisters hit highly populated areas really made heavy casualites inevitible, unfortunately.

Fatalities-wise, this may end up close to the Super Outbreak, but in terms of scope, not quite. 1974 had strong/violent tornados from the deep South all the way up to nearly Canada...13 different states, I believe.

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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.

Ok now that I am thinking about what your saying. I am sure they want more man made structures than trees before giving out an EF4 or EF5 rating. A bare concrete slab and a fully leafed tree would make me question the structural integrity of the home.

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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.

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.

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Yeah, the fact that some of the most violent and long-lived twisters hit highly populated areas really made heavy casualites inevitible, unfortunately.

Fatalities-wise, this may end up close to the Super Outbreak, but in terms of scope, not quite. 1974 had strong/violent tornados from the deep South all the way up to nearly Canada...13 different states, I believe.

The super outbreak might have covered a larger area but the concentration of so many tornadoes over a smaller area makes this more impressive in some ways.

What a horrific year though. Before this outbreak, there was a report on tv there had been 70 billion dollars worth of damage so far this year or that would be the expected number for the season. That number is going to rise obviously.

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This has to be one of the deadliest U.S. weather disasters in the past 50 years...certainly the worst since Katrina.

Already the 3rd worst in the last 50 years and 9th worst in the last 100.

According to Wikipedia (yeah, I know):

1974 - 317+ deaths

1965 - 256+

1953 - 247+

1936 - 454+

1932 - 330+

1925 - 747+

1920 - 243+ and 280+

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