OUN ratings from 5/4-5/5?

[Tony Lyza]

I know that OUN was having difficulty in reaching the Vici and Arnett areas to do surveys for those tornadoes, but it's been awhile. Have any ratings been assigned to those tornadoes (Arnett area 5/4, Vici area 5/5)?

 

[Jeff Snyder]

The only tornado for which I see a rating assigned was the tornado that hit Sweetwater on 5-5 --> see http://www.srh.noaa.gov/oun/tornadodata/ok/tornado2007.php

 

[Dick McGowan]

What about Macksville/St. John, KS tornadoes near dusk on 5/5? I assume it would be very difficult for them to get an accurate rating, since several of the tornadoes tracked over the exact same spot as the night before. I looked back at the video and drove by the area on 5/22. A farm was nearly hit twice in a row (missed by 100 yards or so) in less than 24 hours.

 

[Brandon Goforth]

I was also curious about the rating on the 5/4 Arnett, OK tornado.

 

[Brian Stertz]

It's been over a month ago and still no official write-ups from DDC or OUN. Has funding and staffing been cut so bad by NOAA that they are not doing timely damage surveys anymore? What's the deal??

 

[Shane Adams]

No idea about OUN but the DDC page has detailed track paths from the 5-4 tornadoes......I'm assuming that is the "write up".

 

[Kiel Ortega]

Arnette never really hit anything so I doubt they would have gone out to do a rating. They did rate Sweetwater, which I think kept them (OUN) from getting up to the Vici area for that tornado damage. It's incredibly difficult to get out and do damage surveys; and they are time consuming! I know when I went out to rate the El Reno tornado, we were there for almost 5 hours and I still would have liked to have taken more time (we were trying to rate 3 tornadoes that day for the PAR and CASA folks and then I blew the tire out on the Lab vehicle ). Patrick Marsh and I went back out to survey tornadoes' damage (grammer, usage? ) near Union City and Minco that happened before the El Reno tornado; these took an entire day (weren't as much surveys as they were damage hunts!)! Since Rick (OUN WCM) is on the board, I won't say too much more on the decision making on doing damage surveys

QUICK EDIT for example: just remembered taking into account driving, surveying, debating a rating and writing it all up, it took almost 13 hours to completely finish the Union City and Minco tornado reports. El Reno in total (minus changing a tire) was about 9 hours.

 

[Jay McCoy]

If you watch Reed Timmer's and Joel Talor's video of the 5/4/07 Arnett, Ok tornado you can see some debris being blown around so it obviously hit something. Maybe just a barn or storage buidling but there was damage. In that case OUN should have done a damage survery. It also destroyed a number of trees. It wasnt a large tornado but you can tell from the video it was pretty violent. I would also like to have know its rating. I though all tornados were suppose to be checked out and rated. Thsi was the only tornado in NW Oklahoma that day so it wasnt like they had dozens to check out. I would like to kow why it wasnt. I wasnt near as close as those guys but still got some good video/pics.

 

[Kiel Ortega]

If you watch Reed Timmer's and Joel Talor's video of the 5/4/07 Arnett, Ok tornado you can see some debris being blown around so it obviously hit something. Maybe just a barn or storage buidling but there was damage. In that case OUN should have done a damage survery. It also destroyed a number of trees. It wasnt a large tornado but you can tell from the video it was pretty violent. I would also like to have know its rating. I though all tornados were suppose to be checked out and rated. Thsi was the only tornado in NW Oklahoma that day so it wasnt like they had dozens to check out. I would like to kow why it wasnt. I wasnt near as close as those guys but still got some good video/pics.

In that case, I still don't think OUN needed to go out and do the survey. Nothing of significance was hit where on-ground investigation would really be needed. I think video/pics of stuff being hit should be sent to the NWS and they could have done the survey via the video/pics (we've had some success at doing this at NSSL using media pictures and Google Earth to locate and rate/classify damage).
At most, most farm outbuildings or trees can get is EF-2...really good trees that get debarked and look "spooky" can get a 3. But sending NWS officials out to survey tree damage or an old farm building that was falling apart anyways, is IMO, a little wasteful considering they have other duties. If you're really curious of a tornado's rating, follow behind, take picutres of the damage and then send them in; EF kit is available publicly (and from what I know, is being updated when they get pictures depicting different DODs) so even someone not really trained in surveys could do a survey that might be satisfactory; further, it would satisfy curiosity as much as help out the NWSFO.

 

[Rob Satkus]

Regarding the Arnett tornado...what seemed to be a well built barn or storage building was destroyed southwest of town at a farmsite and there was significant tree damage at the sight as well...this is based off media aerial shots...from what I could tell, this was not an old, decrepit building either. I am no expert but just from the video it looked to be high end EF-1 to EF-2...the tree damage seemed impressive. But once again, this was just based on a helicopter shot seen on the tee vee. I know Val Castor has submitted his video (which, no offense to Reed and the boys, was better in my opinion as he was just as close and podded...) to the NWS. I think when all is said and done, they will get it right. I am very curious to hear about the late night Vici wedge. If no survey was done, that really surprises me as this was a large tornado that did cause damage. That same day Tom Pastrano and I saw 4 tornadoes from near Roll to just east of Arnett on the storm just north of the Sweetwater cell, but as best we could tell, nothing was hit other than trees, so although a couple of the tornadoes were significant in appearance, I would imagine they will all go down as EF-0

 

[Jeff Snyder]

I am very curious to hear about the late night Vici wedge. If no survey was done, that really surprises me as this was a large tornado that did cause damage. That same day Tom Pastrano and I saw 4 tornadoes from near Roll to just east of Arnett on the storm just north of the Sweetwater cell, but as best we could tell, nothing was hit other than trees, so although a couple of the tornadoes were significant in appearance, I would imagine they will all go down as EF-0

It's worth noting that a tornado that only damages trees does not need to be rated (technically) EF0. There are two damage indicators (DIs) for trees -- DI 27 (hardwood tree) and DI 28 (softwood tree). The upper-bound for the highest degree of damage (DOD) for DI 27 is 167 mph, the upper-end of the EF3 category. Granted, I'm not sure that such a DOD (and the choosing of the upper-bound) was experienced in this case, but it does go to show that very high-end tree damage can be used to rate a tornado as strong as an EF3. For the accuracy of the tornado database, I would hope all tornado damage would be assessed, especially since the "it only hit trees, so we can't do an assessment" argument isn't as valid as before given that we have DIs for tree damage. I know Curtis Alexander's work with the DOW data indicates that, for the supercells on which they have data, the most common tornado is not of EF0 strength (I think the most common tornado intensity produced by supercells they captured was EF2). This is getting off-topic, however. I do think we may find that EF0 tornadoes do not constitute the largest number of supercell tornadoes. However, we won't really know this if assessments aren't performed and if damage is only "assumed" to be EF0.

See the description of DIs at http://www.spc.noaa.gov/efscale/ef-scale.html (click on DI27 and DI28). Note that the SPC page on the EF-scale does not have the most updated information. For example, DI2 (one- or two-family residences) now can be used to classify EF5 (upper-bound at 220mph), not limited to EF4 (upper-bound at 198mph) as an older version on the SPC server has. AFAIK, the latest version of the EF-scale can be viewed at http://www.wind.ttu.edu/EFScale.pdf

 

[Rob Satkus]

It's worth noting that a tornado that only damages trees does not need to be rated (technically) EF0. There are two damage indicators (DIs) for trees -- DI 27 (hardwood tree) and DI 28 (softwood tree). The upper-bound for the highest degree of damage (DOD) for DI 27 is 167 mph, the upper-end of the EF3 category.

Yeah, I am aware about the tree damage indicators, but I should have been more specific in my post. I was assuming, based on what has been posted about the lack of a survey and or the lack for a need to survey (I must humbly disagree with that policy, as an outsider) that these tornadoes would go down as EF-0, since no one will see what,if any damage was caused. We didn't see any tree damage, other than a few limbs down on Hwy 283 south of Arnett where one tornado crossed, but given the size and length of a couple of the tornadoes, there must be tree damage out there. I don't know if any EM's from that area have gone looking for damage, which will make a difference obviously.
I know that staffing can be an issue as well as other concerns, such as the fact that was a very busy period and surveys aren't a priority with ongoing severe weather, but some of these tornadoes were siginificant, not the run of the mill brief touchdown open field type. That is why I disagree with the no survey needed policy. But then again, I don't work for the NWS so I obviously don't know what goes on or is going on regarding these tornadoes, like everyone else I am just curious. I know there is an NWS'er or two on here as well as some SPC folks...can you guys shed any light on things? And...this is in no way a knock on the NWS...us wx weenie types get all paranoid if info isn't fed to us right away!

Rob

 

[Jim Tang]

I suspect the NWS have done the surveys but have chosen to not release them to the public. With the destruction the May 4 outbreak caused, releasing the May 5 outbreak information could lead to confusion. I've already seen enough Youtube videos where tornado video from May 5 is labled as the Greensburg tornado by one of the commenters. Also keep in mind that OUN almost never releases their survey information unless it's a really big event (May 29, 2004 comes to mind).

 

[Ilya Neyman]

Regarding the NW Oklahoma tornado of 5/4 it's a little known fact that the now famous video of the violently rotating slender tube near the town of Arnett was actually the SECOND tornado from that storm. We were coming up on the storm from the ESE that evening and observed a cone-stovepipe type tornado out of a well-defined wall cloud while about 25-30 or so miles out. I reported this as a (visually) large tornado to KOCO at the time and we watched it as it was on the ground for quite some time, with my best estimate for about 10+ minutes or so after we got into view of it (already on the ground when we first spotted it). The tornado then reconfigured its shape becoming angled and more narrow as we paralleled the storm on Hwy 34 toward Vici. When we pulled into Vici the second, and famously viewed tornado was on the ground to our west crossing Hwy 60. This tornado was evident as a slender/tall tube extending from a relatively higher cloud base, with no visible wall cloud, thus very different from its predecessor earlier.

I've talked to a number of chasers out that day including Reed and Joel and so far have not personally come across anyone else that saw the first and larger tornado. Reed and Joel punched in from the northeast as they explained it and the rain core obstructed their view to the south until they got into close position for their footage.

If anyone else saw that first tornado(s) feel free to post here!

 

[jladue]

It's worth noting that a tornado that only damages trees does not need to be rated (technically) EF0. There are two damage indicators (DIs) for trees -- DI 27 (hardwood tree) and DI 28 (softwood tree). The upper-bound for the highest degree of damage (DOD) for DI 27 is 167 mph, the upper-end of the EF3 category. Granted, I'm not sure that such a DOD (and the choosing of the upper-bound) was experienced in this case, but it does go to show that very high-end tree damage can be used to rate a tornado as strong as an EF3.

The tornado south of Arnett (night of May 5) did max out the DOD for hardwood trees where it hit a friend's hunting camp near the Canadian river. Several vehicles nearby couldn't be found except for the hood of one car 1/2 mile to the southeast. So I'm not sure about going to max out the upper bound wind. The expected wind speed is enough for an EF3 rating. This DOD for trees would be enough to dismember a vehicle.

For the accuracy of the tornado database, I would hope all tornado damage would be assessed, especially since the "it only hit trees, so we can't do an assessment" argument isn't as valid as before given that we have DIs for tree damage.

I agree that every tornado should be surveyed if there were only a huge number of surveyors available to do the job. The local WFO is overwhelmed and I'm sure they would appreciate having damage pictures sent in. The most useful shots would be to take a zoomed out view, and then some detailed shots of any DI. It would really help to forward exactly where you'd taken the shots too.

I know Curtis Alexander's work with the DOW data indicates that, for the supercells on which they have data, the most common tornado is not of EF0 strength (I think the most common tornado intensity produced by supercells they captured was EF2). This is getting off-topic, however. I do think we may find that EF0 tornadoes do not constitute the largest number of supercell tornadoes. However, we won't really know this if assessments aren't performed and if damage is only "assumed" to be EF0.

I have to differ you here. Take a look at this distribution of tornado strength between discrete vs. linear modes from Elaine Godfrey's work here. I remember the sampling of tornadoes documented by the DOWs to be skewed toward high end relative to other climatologies. BTW, if there were a rating one step below EF0, the numbers would probably be exponentially bigger. I believe even the DOW data would show the proliferation of accessory vortices found around mesocyclonic tornadoes. The strength distribution profile found in the more modern tornado climatology agrees very well with strength distributions of other natural events (e.g., earthquakes, volcano eruptions, CMEs, etc.)


regards,

Jim