AbsolutZero Posted March 10, 2012 Share Posted March 10, 2012 To answer JoMo more in depth... Very good write up, OceanStWx! If you can look at his screen captures of the storm in Cobb and Fulton counties in his post closely, you'll see that the low cc occurs in the inflow notch region of the storm where no precip is occurring. The low cc in Haralson and Paulding images occurs within the higher reflectivity area near the hook. Here are some links to kmz files of the TDS location and times as well as the damage survey contours and damage points. Overlay them together in Google Earth. http://db.tt/0QzuqJal http://db.tt/FfGfBy4z Link to comment Share on other sites More sharing options...
AbsolutZero Posted March 10, 2012 Share Posted March 10, 2012 I figure it's a lock that the March storm of the month will be this outbreak right? You guys must be clairvoyant. This storm IS the WDTB SOTM for March! Link to comment Share on other sites More sharing options...
OceanStWx Posted March 10, 2012 Share Posted March 10, 2012 Hey all, this is SNELSON@FFC. That track was surveyed on the ground twice and also by air. Cobb county was also surveyed and found a weak/brief EF1. Very interesting event. I have been studying the TDS in depth since we upgraded KFFC. *Amazing* dataset that surpassed my expectations. I was in Starkville at the SE Severe Storms Symposium (presenting on the Coweta/Fayette county December and January TDSs of all things) on Friday night and watched the event unfold on TWC and nwschat. I returned home and studied the data. Without going into details, there were indeed false detections by forecasters as well as the media once a well defined inflow notch developed in Cobb, Fulton and other counties to the east. Our warnings and statements continued the mention of debris until the last warning on that storm. That said, it was *very* impressive that the forecasters correctly identified the TDS back in Haralson county so quickly and incorporated into the warnings and statements. I'd rather have this rapid detection and incorporation into warnings along with an hour of false positives, than no detection at all! Kudos to the forecasters on deck that night. Based on research from UAH and the ARMOR dual-pol radar, you really do not have a TDS without cc < 0.8, a velocity couplet, AND reflectivity values > 30dbZ. Once the storm entered Cobb county, the low correlation coefficient values were not occurring in the reflectivity hook where the tornado should be but in the inflow notch VERY close (~1/2 mi northeast) to where it should be (at the tip of the hook). The low cc values were indeed superimposed on the velocity couplet but not in an area of higher reflectivity. A very easy mistake to make, particularly when there are NO experts at interpreting real-time dual-pol anywhere! Anyways, we'll keep learning as we go. For now, I'm leading training in the NWS to include reflectivity > 30dbZ *and* knowledge of storm structure to better interpret the TDS. I will be posting some of this data to our web page on the event and/or our facebook page. Steve What I found most interesting about your storm was that it ran the gamut of possibilities. It developed the TDS when it got into your CWA, then it started showing the false positive, then it put another tornado down without showing a TDS. I do think the inclusion and phrasing of debris statements in the warning text were great. And while some false positives triggered inclusion into later statements, it had already put multiple tornadoes down and still maintained a strong velocity signature, it's not as if the warning forecaster was going to stop issuing TORs. Link to comment Share on other sites More sharing options...
AtticaFanatica Posted March 10, 2012 Share Posted March 10, 2012 Based on research from UAH and the ARMOR dual-pol radar, you really do not have a TDS without cc < 0.8, a velocity couplet, AND reflectivity values > 30dbZ. Once the storm entered Cobb county, the low correlation coefficient values were not occurring in the reflectivity hook where the tornado should be but in the inflow notch VERY close (~1/2 mi northeast) to where it should be (at the tip of the hook). The low cc values were indeed superimposed on the velocity couplet but not in an area of higher reflectivity. A very easy mistake to make, particularly when there are NO experts at interpreting real-time dual-pol anywhere! Anyways, we'll keep learning as we go. For now, I'm leading training in the NWS to include reflectivity > 30dbZ *and* knowledge of storm structure to better interpret the TDS. I will be posting some of this data to our web page on the event and/or our facebook page. Steve How did you translate C-band polarimetric obs to S-band since the scattering properties can be quite different? Link to comment Share on other sites More sharing options...
blackjack123 Posted March 10, 2012 Share Posted March 10, 2012 Respectfully disagree. The tornadoes this goaround were clearly less violent than 4/27. The tornadoes on 4/27 literally wiped homes off the map. Here we still have the debris laying around (and in many cases e.g. Moscow and West Liberty, many the walls are even still standing). Also, remember that the Cordova *low-end* EF4 threw a 2-ton utility trailer a mile, which ended up impacting the ground with enough momentum to create a 2.5-ft deep crater. Nothing like that happened in the tornado you are referring to, and it only hit trees and mobile homes at that intensity (which only go up to EF3 anyway). I agree with you. This tornado outbreak was not nearly as violent as the April 27th tornado outbreak from last year. Still very impressive for this time of the year. I would say it was comparable to the Super Tuesday Outbreak of 2008. 9 EF3's and 2 EF4's in this outbreak. That one had 5 EF3's and 5 EF4's. Link to comment Share on other sites More sharing options...
andyhb Posted March 10, 2012 Share Posted March 10, 2012 I agree with you. This tornado outbreak was not nearly as violent as the April 27th tornado outbreak from last year. Still very impressive for this time of the year. I would say it was comparable to the Super Tuesday Outbreak of 2008. 9 EF3's and 2 EF4's in this outbreak. That one had 5 EF3's and 5 EF4's. Fred and I were discussing the similarities between 3/2's setup and Super Tuesday on AIM before the event, although this one did most of its damage further north while Super Tuesday was centered further south. Link to comment Share on other sites More sharing options...
RCNYILWX Posted March 10, 2012 Share Posted March 10, 2012 Based on research from UAH and the ARMOR dual-pol radar, you really do not have a TDS without cc < 0.8, a velocity couplet, AND reflectivity values > 30dbZ. Once the storm entered Cobb county, the low correlation coefficient values were not occurring in the reflectivity hook where the tornado should be but in the inflow notch VERY close (~1/2 mi northeast) to where it should be (at the tip of the hook). The low cc values were indeed superimposed on the velocity couplet but not in an area of higher reflectivity. A very easy mistake to make, particularly when there are NO experts at interpreting real-time dual-pol anywhere! Anyways, we'll keep learning as we go. For now, I'm leading training in the NWS to include reflectivity > 30dbZ *and* knowledge of storm structure to better interpret the TDS. I will be posting some of this data to our web page on the event and/or our facebook page. Steve Has that research been posted anywhere? Based on the great work by OceanStWx, I showed his post to colleagues at WFO Chicago and we've had a good discussion the last 2 days about the radar signatures from the event in your area. I'm going to present the case at the LOT spring severe wx workshop and it might be good to have a slide with the research from UAH and the ARMOR radar. I'm also may include radar frames from Springfield, MO for the Branson tornado case, which was a great example of the utility of the CC TDS, because the the other radar signatures were not as clear cut as to where the tornado was located. Overall, completely agree, the forecasters at FFC did a great job with the event. Cases like this are a huge help for all of us to build a knowledge base to best incorporate Dual Pol data into the warning process. Link to comment Share on other sites More sharing options...
blackjack123 Posted March 10, 2012 Share Posted March 10, 2012 Fred and I were discussing the similarities between 3/2's setup and Super Tuesday on AIM before the event, although this one did most of its damage further north while Super Tuesday was centered further south. The other outbreak that was from April 16, 2011 of last year was also somewhat similar to this outbreak. It was later in the season although, furher southeast, and it had 13 EF3's. They all seem to match on strong/violent tornadoes and number of fatalities. The April 16th outbreak killed 39, this one killed 41, and the Super Tuesday Outbreak killed 57 or 58. Like it was said not nearly as violent as April 27th of last year but still pretty darn scary. Link to comment Share on other sites More sharing options...
CoastalWx Posted March 12, 2012 Share Posted March 12, 2012 I was just reading a couple of blogs describing some false TDS features before I came across the recent posts from OceanSt and Absolutzero. It shows you how you have to cross check with other features like ZDR, reflectivity, cc..etc, but it's a pretty cool feature to back up the enhanced wording in some of those warnings. Link to comment Share on other sites More sharing options...
Calderon Posted March 12, 2012 Share Posted March 12, 2012 Now home security footage from the Harrison, TN EF-3. Link to comment Share on other sites More sharing options...
Ginx snewx Posted March 12, 2012 Share Posted March 12, 2012 Now home security footage from the Harrison, TN EF-3. Holy crap that was close for those guys, wonder how the dogs fared. Man that went from calm to unreal in seconds. Link to comment Share on other sites More sharing options...
mappy Posted March 13, 2012 Share Posted March 13, 2012 I hope those dogs are ok Link to comment Share on other sites More sharing options...
thewxmann Posted March 13, 2012 Share Posted March 13, 2012 ILN has released new photos of the damage in Kenton County: Source Link to comment Share on other sites More sharing options...
Ginx snewx Posted March 13, 2012 Share Posted March 13, 2012 I am intrigued by this video, by the white burst of fast moving light seen on all the cameras. Some optical phenomena explodes out of the woods. Link to comment Share on other sites More sharing options...
JoMo Posted March 13, 2012 Share Posted March 13, 2012 I am intrigued by this video, by the white burst of fast moving light seen on all the cameras. Some optical phenomena explodes out of the woods. Got any times on the video when this occurs or more information? Link to comment Share on other sites More sharing options...
Ginx snewx Posted March 13, 2012 Share Posted March 13, 2012 Got any times on the video when this occurs or more information? Yea around 348 and 531 and from 612 to 631 ,watch lightning hit the house then the weird optical ,then it just exploded out of framr right before the house exploded check it out. At 540 you an see the light by the House suddenly again shoot out of frame. The light that shoots out of the woods over the pool is cool too. Link to comment Share on other sites More sharing options...
AbsolutZero Posted March 13, 2012 Share Posted March 13, 2012 How did you translate C-band polarimetric obs to S-band since the scattering properties can be quite different? I'm not an omniscient radar expert, but as I understand from the literature, CC is not affected as much by attenuation and non-uniform beam filling as ZDR. Read Bluestein's paper on TDS with mobile X-band, MWR 2007. There's a few other references too. If you actually look at the ARMOR data during TDS cases, they look almost identical to 88D TDS cases. Chris Schultz EJOM article is under review and should be up in the near future. Link to comment Share on other sites More sharing options...
AbsolutZero Posted March 13, 2012 Share Posted March 13, 2012 Has that research been posted anywhere? Based on the great work by OceanStWx, I showed his post to colleagues at WFO Chicago and we've had a good discussion the last 2 days about the radar signatures from the event in your area. I'm going to present the case at the LOT spring severe wx workshop and it might be good to have a slide with the research from UAH and the ARMOR radar. I'm also may include radar frames from Springfield, MO for the Branson tornado case, which was a great example of the utility of the CC TDS, because the the other radar signatures were not as clear cut as to where the tornado was located. Overall, completely agree, the forecasters at FFC did a great job with the event. Cases like this are a huge help for all of us to build a knowledge base to best incorporate Dual Pol data into the warning process. Yes, as mentioned earlier, its coming to the EJOM. If you're in the NWS, our office is also hosting a 88D storm of the month on the 28th and I'm presenting to SR offices on 20th and some CR SOO's on the 22nd. I can pass on a powerpoint that has screen caps if you'd like. The Branson case is supposedly going to be the April storm of the month. Link to comment Share on other sites More sharing options...
AtticaFanatica Posted March 13, 2012 Share Posted March 13, 2012 I'm not an omniscient radar expert, but as I understand from the literature, CC is not affected as much by attenuation and non-uniform beam filling as ZDR. Read Bluestein's paper on TDS with mobile X-band, MWR 2007. There's a few other references too. If you actually look at the ARMOR data during TDS cases, they look almost identical to 88D TDS cases. Chris Schultz EJOM article is under review and should be up in the near future. You would be correct. However, the point of my question was that Mie scatterers (which can be large raindrops at higher radar frequencies) will impact CC at C-band differently than at S-band. For example, in pure rain, CC is .98+ at S-band and .93 at C-band. If there's a quantitative algorithm being developed, then the actual numbers may be impacted. Bluestein et al. (2007b) discussed CC numbers in debris (below 0.5 generally), but those weren't intended for quantitative operational use at S-band, obviously. For instance, Ryzhkov et al. (2005) found CC below 0.8 in tornadoes at S-band compared to the .5 found by Bluestein et al. (2007b) at X-band. Link to comment Share on other sites More sharing options...
blackjack123 Posted March 13, 2012 Share Posted March 13, 2012 ILN has released new photos of the damage in Kenton County: Source Defenitely agree with the upgrade to an EF4. Two of them homes were completely swept away along with visible circular marks on the ground from the tornado. Link to comment Share on other sites More sharing options...
Bryan Wood Posted March 13, 2012 Share Posted March 13, 2012 LMK has posted over 100 pics of the Southern IN EF4, which you can see here: http://www.crh.noaa.gov/Image/lmk/03022012_EF4.htm One picture grabbed my attention due to ground gouging. Do you think this was caused by a car being dragged along the ground? Link to comment Share on other sites More sharing options...
QVectorman Posted March 13, 2012 Share Posted March 13, 2012 Yea around 348 and 531 and from 612 to 631 ,watch lightning hit the house then the weird optical ,then it just exploded out of framr right before the house exploded check it out. At 540 you an see the light by the House suddenly again shoot out of frame. The light that shoots out of the woods over the pool is cool too. Yeah, I noticed the same thing and was wondering what that was. Link to comment Share on other sites More sharing options...
DBriedis Posted March 13, 2012 Share Posted March 13, 2012 Looks like the wind carrying flaming material away. It also looks almost like some sort of gas venting, like a ruptured propane tank perhaps? Link to comment Share on other sites More sharing options...
Ginx snewx Posted March 14, 2012 Share Posted March 14, 2012 Yeah, I noticed the same thing and was wondering what that was. Weird and look at this from the Pharmacy security camera Link to comment Share on other sites More sharing options...
hm8 Posted March 14, 2012 Share Posted March 14, 2012 My guess is its just water on the lens moving around, but the crazy part of me wants to ay it's ball lightning Link to comment Share on other sites More sharing options...
Ginx snewx Posted March 14, 2012 Share Posted March 14, 2012 My guess is its just water on the lens moving around, but the crazy part of me wants to ay it's ball lightning My thoughts are varied but different cameras and angles suggest it was not the camera, ball lighting is a theory. Wouldnot have thought anything of it until is showed in two vids and 4 different cameras. Link to comment Share on other sites More sharing options...
cyclone77 Posted March 14, 2012 Share Posted March 14, 2012 I'm guessing it's just a spec of small debris quickly zipping by the camera lens at a close range. At the 1:15 mark there's a similar looking feature in the bottom/right quarter of the frame. EDIT: This was in reference to the last security camera footage. The other security camera footage is very interesting. Link to comment Share on other sites More sharing options...
RCNYILWX Posted March 14, 2012 Share Posted March 14, 2012 Yes, as mentioned earlier, its coming to the EJOM. If you're in the NWS, our office is also hosting a 88D storm of the month on the 28th and I'm presenting to SR offices on 20th and some CR SOO's on the 22nd. I can pass on a powerpoint that has screen caps if you'd like. The Branson case is supposedly going to be the April storm of the month. Excellent, looking forward to seeing the research there. I'm in the NWS, so I'd like to get my office on the storm of the month call on the 28th. Is there a webinar invite being sent out? Hopefully the LOT SOO is on the call on the 22nd as well. That would be great if you could pass on the powerpoint with screen caps. Thanks. When I present at our svr wx workshop, I'm going to attempt to include both the case from your CWA and the Branson case. Link to comment Share on other sites More sharing options...
QVectorman Posted March 14, 2012 Share Posted March 14, 2012 My thoughts are varied but different cameras and angles suggest it was not the camera, ball lighting is a theory. Wouldnot have thought anything of it until is showed in two vids and 4 different cameras. Yeah, I tried to dismiss it as a water drop on the lens but there are a few other shots that have water droplets on it and you can definitely tell the difference. Plus, you can tell it's in the background and not foreground. I'm thinking since we have never really seen much data and footage from inside tornadoes that over the next couple years more footage like this and from TIV like vehicles will begin to pop up. Just a guess but I was thinking maybe it is an area where extremely low pressure develops for some unknown reason yet and causes water to condense creating a cloud/contrail like entity. Maybe even a combo of expansion cooling bring the parcel down to it's DP producing condensing...possibly related to lower pressures. Edit: Watched it more closely, it appears to happen around trees and obstacles etc. You see this on an aircraft wing when you're taking off if there is enough moisture in the air. It's called wing tip vortices. There is speed shear around the trees so vortices develop spinning at a very high speed producing a region of very low pressure.Then the local temperature in the low-pressure regions drops due to expansional cooling. When the local temp drops below the local dewpoint, condensation of water vapor results in the core of the vortex, making it visible. It's most obvious at 531 Link to comment Share on other sites More sharing options...
mappy Posted March 14, 2012 Share Posted March 14, 2012 Could it just be light reflection off the rain as it is being blown across grass/pavement? Link to comment Share on other sites More sharing options...
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