Hallam and Greensburg Similarities

[Gabe Garfield]

I'm just going off of what it was during the daylight hours. The Hallam wedge didn't get really big until right at dark (at least dark under the storm). Up until then though there wasn't any rain around the first wedge that crossed the highway and the second white cone that turned into the big brown wedge that went on to hit Hallam. At least where I was just East and Southeast of the tornado I never got a drop of rain on me and there wasn't any wrap around obscuring my view. Once again though, once it got huge right before it hit Hallam, that is a different story.

This is true. Most of the visibility problems during the daytime part of this event were due to dust obscuring the condensation funnel, rather than intervening rain curtains.

Gabe

 

[Tony Cook]

I'm just going off of the 205mph, not just that an old F3 wind speed is now an F5 winds speed. The OKC F5 had winds >315mph. The Greensburg tornado was nothing to sneeze at obviously, but it is nowhere close to an old F5 like the one that hit OKC. We hadn't had an F5 since 1999, and now we are going to have multiple F5's every year. I think it is a little BS that there isn't going to be a distinction made between tornadoes that have 200mph winds and ones that have winds over 300mph. There is a huge difference in reality between the two, but both will now be an EF5. I don't know the exact peak winds for the Hallam tornado either, but I would bet it was stronger and we know it was bigger.

Michael,

This has already been discussed a little bit in another thread. Take a look starting here (click the arrow by rdale's name to jump to that part of the thread):

Stuart - take a look at some of the training material on http://www.wdtb.noaa.gov As indicated above, an EF5 today translates to an F5 last year, that's why they kept the numeric designations the same.

And some additional threads from the past about the EF scale. There was even talk that an EF5 rating would be impossible to achieve based on the damage criteria:

http://www.stormtrack.org/forum/showthread.php?t=10649&highlight=EF+SCale
http://www.stormtrack.org/forum/showthread.php?t=10847
http://www.stormtrack.org/forum/showthread.php?t=8526&highlight=EF+SCale

It is incorrect to assume a wind speed of 205 mph from the Greensburg tornado, in the first place. The F and EF scales are damage scales, with windspeeds being inferred subjectively based on damage. It is also incorrect to compare an inferred wind speed of 205 mph from a new EF5 tornado to wind speeds of 300+ mph from an old F5 tornado. Until we can precisely measure the actual wind speed in every torando, or until an improved system is put in place (EEF?), this method of rating will have to suffice.


TonyC

 

[Kiel Ortega]

I don't know much about the new EF scale either, but I think it just took what we know about modern engineering and construction into consideration and they found that weaker winds can do more damage.
I'm just going off of the 205mph, not just that an old F3 wind speed is now an F5 winds speed. The OKC F5 had winds >315mph. The Greensburg tornado was nothing to sneeze at obviously, but it is nowhere close to an old F5 like the one that hit OKC. We hadn't had an F5 since 1999, and now we are going to have multiple F5's every year. I think it is a little BS that there isn't going to be a distinction made between tornadoes that have 200mph winds and ones that have winds over 300mph. There is a huge difference in reality between the two, but both will now be an EF5. I don't know the exact peak winds for the Hallam tornado either, but I would bet it was stronger and we know it was bigger.

This is probably off topic, but obviously people still don't get the damage scales. The new EF-scale shows that you CANNOT distinguish damage from 200 MPH and 300 MPH for most constructions and buildings. I don't think the EF-scale is going to add any more EF-5s to the system...in fact, I think it's really difficult to get there as using most damage indicators (especially those that are most frequently used like trees, metal buildings and barns) will only tell you up to EF-4. And for quality homes, it would take a really strong tornado to wipe the foundation clean to get up to EF-5 rating.

How do you know the Greensburg tornado wasn't anything like OKC? Were you there? Did you measure the winds with something reliable at 150+ MPH? If I recall, the OKC/Moore tornado had a fairly THIN F-5 region (6 houses in Moore were rated F5 if I am looking at some graphics correctly http://www.nssl.noaa.gov/users/speg/public_html/papers/3may99wf/ ). Yeah, it sucks we can't tell the difference between 200 MPH and 300 MPH---but that's just a result of our construction and measurement limitations. But I think it's more BS to just assign huge wind speeds when we can't even tell if that was the windspeed (and if anyone is thinking of bringing up the DOW data, it took a lot of unfolding to come to the 318 MPH estimate, so who knows---futher they don't know what height that measurement was). The training for the EF-scale is online via WDTB; the EF-kit which is what is used for the ratings is included on there (http://www.wdtb.noaa.gov/courses/EF-scale/index.html)

 

[Jim Tang]

Hey Mike P, just reading this has sent a chill right through me, because there have been times over the past few days, that Hallam, NE, has came to mind, when looking up the images, structure, etc of the tornado and the meso and like you say, both the similarities of both Hallam, NE and Greensburg, KS, have both been completely swamped by a beastly monster.

There is another slight oddity as well, as reguards the damage paths... In Hallam, only a small portion of the tornado, had went over the town, as the other 70% of the damage path was to the East of the town, and in Greensburg, there was about 1/5 of the tornadoes path width, that was of to the East of the town there too, but in both cases, I feel that this was simply due to the magnitude of the tornadoes width

I will say though that the RFD may have been increasing the meso and/or tornado's rotational speed and momentum, as I had found using the tornado machine, that when I was using the central fan, (Used to make the tornado) the tornadoes were of moderate strenth/width, but when I added any kind of extra inflow, the tornado naturally increased in strength (Wind speed) and in width and I feel that this may have been a factor also

Those pictures that you have taken Mike S, are incredible, especially the first pic, as Mike P has mentioned

There is one thing that I'm wondering though, was the Hallam, NE '04 supercell, not an HP storm, or was it an LP Supercell also?

Willie

Willie,

The Hallam cell was strongly HP. The Greensburg cell was on the high precipitation side of classic.

 

[Mikey Gribble]

Kiel, I am just going off of the DOW mesuring winds >315mph in the OKC tornado and the survey from Greensburg saying peak gusts were at 205mph. The OKC measurments have nothing to do with damage and I remember hearing the height of the measurement fromt the DOW was something like 50-100ft above the surface, so yeah you could take a little off that for surface wind speeds, but not 100mph.

 

[Mikey Gribble]

I can't figure out how to find the old reports thread from Hallam, but if you look at the pictures there really wasn't any rain around the tornado or under the updraft before dark Jim. The first tornado that was a wedge when it crossed the highway was very tough to see, but it was obscured by dust being picked up, not rain. So on that one I could see somebody that was a mile or more away thinking it was HP. The second tornado that went on to hit Hallam was very easily visible early on. It was a white cone and then transitioned to a dirt filled wedge. I won't say that it didn't go HP right before it hit Hallam at dark though, because once again I don't know. I wasn't under the updraft any more for obvious reasons. I wanted nothing to do with that beast.

 

[Jeff Snyder]

The Hallam day... Dusty dusty dusty. I actually thought that the tornado that would later hit Hallam had actually lifted a good amount of time before it passed through that town. It became so large, and everything was so dusty, it looked like a big black abyss.

I didn't take any actual pictures that day (that was before I bought my 20D), but I did take a lot of video. The best I could do is the still at --> http://www.tornadocentral.com/chasing/2004/05222004/05220424.php . Now, whether that's the edge of the tornado or a tight edge of the wrap-around precipitation is debatable. If the cloudbase were to extend a bit more into the foreground above that feature, I'd be more willing to think it's the actual tornado. As it is now, it looks like it extends well into the vertical, which makes me think it's precip.

At any rate, as darkness set in, I'm confident in saying that the storm was HP, as the radar imagery suggests (the "weak-echo" hole surrounded by very high reflectivity). Before darkness, I'd say it was classic, as we didn't see much in the way of wrap-around or RFD precip.

 

[Jim Tang]

I can't figure out how to find the old reports thread from Hallam, but if you look at the pictures there really wasn't any rain around the tornado or under the updraft before dark Jim. The first tornado that was a wedge when it crossed the highway was very tough to see, but it was obscured by dust being picked up, not rain. So on that one I could see somebody that was a mile or more away thinking it was HP. The second tornado that went on to hit Hallam was very easily visible early on. It was a white cone and then transitioned to a dirt filled wedge. I won't say that it didn't go HP right before it hit Hallam at dark though, because once again I don't know. I wasn't under the updraft any more for obvious reasons. I wanted nothing to do with that beast.

I meant after dark, the Hallam storm looked HP from a radar standpoint, just to clarify.

 

[mike scantlin]

ok. i think that there are alot of people that have no idea what they are talking about when trying to compare the old scale to the new. you said that this tornado peaked at approx. 205. and that on the old scale it would have been a 3. thats wrong. thats why we needed a new scale. if you really think that the damage you saw was f-3 damage, you're crazy. thats what the new scale is for. it doesnt take 315mph to completely tear a house away. you're thinking that they didnt change the damage degrees, but they did. i'm having a hard time describing what i'm thinking.

starting over. the damage done would not have been rated F3. its harder to achieve the 5 rating with the new scale. the wind speeds were lowered in comparison to damage. get it? the wind speeds in correlation to the damage they produce is what has changed between scales. so saying that both scales would rate the top winds at 205 is ridiculous. if there were a way to put both scales side by side, you could easily get what i'm saying. sometimes i'm not great at getting my thoughts accross without being a dick, so i'll let someone else try to explain what i'm saying.

 

[Jeff Snyder]

OK Guys, let's try to keep this on topic. If you want to continue the EF-scale vs. F-scale debate, please do so in a different thread (or re-read previous threads on this topic). Thanks!

P.S. -- Let's all try to remain friendly!

 

[cdcollura]

I think the Hallam F4 at 2.5 miles wide had peak winds around 250 MPH (correct me if I am off).

Would the Hallam, NE storm on May 22, 2004 also be an EF-5 (on the new enhanced F scale)?

 

[Brett Roberts]

I've been hearing that 205 mph figure thrown around a lot the past few days, so just for clairification, was that actually measured/estimated somehow, or simply based on damage (i.e., the minimum for the EF-5 category)?

 

[Mikey Gribble]

I don't think the Hallam tornado had a direct hit on any structures. I could be wrong, but I think the damage that gave it the F4 rating was from Hallam which was towards the edge of the tornado. Plus it was on the western edge of the tornado, so on the right side winds would have been even higher (not sure what storm motion was that day though).

 

[Mikey Gribble]

Don't know on that Brett. I just saw it on the news.

 

[Zac Flamig]

I've been hearing that 205 mph figure thrown around a lot the past few days, so just for clairification, was that actually measured/estimated somehow, or simply based on damage (i.e., the minimum for the EF-5 category)?

205 MPH was the number that the WCM/MIC put the tornado at when doing the damage survey(atleast I believe this was the case, I heard that number that day while out there). This is merely a result of using the EF scale and tweaking the degree of damage to produce an estimate of the wind speeds.