thewxmann Posted April 30, 2017 Share Posted April 30, 2017 1 hour ago, Drz1111 said: I'd love to hear a postmortem on how the Van Zandt Co. tornados happened today. It didn't look like there was nearly enough bulk shear for strong rotating updrafts in the midlevels, and visually the updrafts looked barely sheared when everything was in the towering cumulus stage, so notwithstanding the good low-level shear I was completely skeptical of tornados literally until the first tail end storm started spinning up. Then all of a sudden that starts strongly rotating; then it's flanking updraft starts to rotate (that turns into the Canton storm) and so on for the next 2 or 3 updrafts. So whatever was happening there, it was repeatable and not a fluke. Also, I was out with Silver Lining Tours thanks to a tip from someone on this forum back in 2016 and obviously today was a home run for me, so thanks to whoever dropped that recommendation back when. They were great and professional. Actually the 0Z NAM last night was the first hint that something would go down today, and the 0Z 3-km NAM was downright impressive. Both models spun up a subtle low in S OK that backed the winds in E TX to southeasterly. Earlier runs, and the GFS, kept the sfc low buried in S TX/MX and so the sfc winds veered along the front. The kicker was the 3-km NAM veered the 500mb flow slightly more towards 0Z and this allowed more of the stronger bulk shear magnitudes to overspread the free warm sector, earlier. These subtle changes in trof geometry were not captured really well by any models until late-game, but made a huge difference in keeping storms supercellular just long enough. Finally, on the mesoscale level, the sfc obs indicated that there was not one main initiating boundary (the cold front out towards 35), but two... one ahead of the cold front, separating the backed windfield from more veered flow closer to the front. Many of the storms initiated on the latter boundary because convergence was stronger along it. Link to comment Share on other sites More sharing options...
SluggerWx Posted April 30, 2017 Share Posted April 30, 2017 This article says 5 lost their lives today - very tragic.http://www.nbcnews.com/news/weather/over-50-hurt-after-tornadoes-hit-east-texas-n752926Sent from my Pixel XL using Tapatalk Link to comment Share on other sites More sharing options...
shaggy Posted April 30, 2017 Share Posted April 30, 2017 34 minutes ago, BuffaloWeather said: That had to be over 1 1/2 wide at one point. Unreal video Yeah it was huge. Seeing the damage to the car dealership is impressive. Lots of cars tossed and the building shredded but the metal framing still mostly intact. Looks strong EF-3ish to me when it hit the dealership. No telling what damage exist we haven't seen yet so who knows what the rating will end up. Link to comment Share on other sites More sharing options...
cstrunk Posted April 30, 2017 Share Posted April 30, 2017 Also remember that all it takes is one location to experience the most severe damage for the EF rating to be increased. No doubt though that this was a strong/violent tornado and it was on the ground for quite a ways. Link to comment Share on other sites More sharing options...
1900hurricane Posted April 30, 2017 Share Posted April 30, 2017 1 hour ago, jojo762 said: Believe the boundary put out by that HP supercell--turned compact MCS-- in Louisiana earlier on in the day played a significant role in storm intensification. The 00Z SHV RAOB was fairly impressive to begin with in the low-levels (ESRH of ~400 m2/s2), but that ambient environment coupled with the boundary and extreme instability in Texas made it all come together... Well all that and very low LCLs. Just another reminder that the 0-1km/0-3km layer are really what matters the most. If you have SHARPpy, you can actually use the KSRV sounding as a starting point and modify it to something close to the near storm environment. I probably overcooked the one I just did by a little bit (my temp/dewpoint is something I recorded a little before I was in position to intercept those storms, and I might have backed and strengthened my surface winds a little too much), but it at least gives you an idea. Link to comment Share on other sites More sharing options...
andyhb Posted April 30, 2017 Share Posted April 30, 2017 5 minutes ago, 1900hurricane said: If you have SHARPpy, you can actually use the KSRV sounding as a starting point and modify it to something close to the near storm environment. probably overcooked the one I just did by a little bit (my temp/dewpoint is something I recorded a little before I was in position to intercept those storms, and I might have backed and strengthened my surface winds a little too much), but it at least gives you an idea. Pretty rare to see such steep mid level lapse rates with such a moisture-laden sounding through the column. A low level environment like that can certainly overcome iffy wind fields further aloft. Saw it on days like 5/22/16, 5/6/15 in N KS, to a lesser extent Vilonia 4/27/14, etc. Link to comment Share on other sites More sharing options...
Quincy Posted April 30, 2017 Share Posted April 30, 2017 6 minutes ago, andyhb said: Pretty rare to see such steep mid level lapse rates with such a moisture-laden sounding through the column. A low level environment like that can certainly overcome iffy wind fields further aloft. Saw it on days like 5/22/16, 5/6/15 in N KS, to a lesser extent Vilonia 4/27/14, etc. Extreme surface-based instability with substantial low-level shear. The mid and upper levels didn't appear to be all that iffy. Sure, more low-level shear than deep layer shear, but good crossovers and 700mb mesoanalysis suggests there wasn't much VBV at all. Some 23z maps: Link to comment Share on other sites More sharing options...
shaggy Posted April 30, 2017 Share Posted April 30, 2017 These have to be two of the dumbest yet luckiest people alive tonight. Roof flies off your barn SEEK SHELTER. Nope they just stand outside in a tornado. Glad they are alive. Link to comment Share on other sites More sharing options...
andyhb Posted April 30, 2017 Share Posted April 30, 2017 I was referring more to the lack of stronger ventilating flow in a very high PWAT/modest bulk shear environment, which would generally result in rapid transition to HP mode and precip-saturated RFDs. Given the intensity of the low level SRH and favorable storm relative inflow (not to mention plenty of low level instability), the latter of those conditions was essentially rendered irrelevant and the results were strong/violent tornadoes. Link to comment Share on other sites More sharing options...
weatherextreme Posted April 30, 2017 Author Share Posted April 30, 2017 Pretty large area of 5% tornado for tomorrow. Most of the area is for the other sub-forums, but looks like we still have LA and some of AR/MO within the outlook. Strong Tornadoes mentioned Mississippi Valley to western slopes of the Appalachians... Taking into account the preceding discussion, uncertainties seem too large to allow for more than an outlook of a categorical slight risk at the present time. But given the strength of the synoptic system and associated wind fields, and at least a corridor of pre-frontal boundary layer moisture characterized by surface dew points in the mid 60s to near 70F, it may not be out of the question that a window of opportunity for considerable severe weather potential could develop this afternoon and evening. This seems mostly likely to be focused near or just east of the Mississippi Valley, and mostly in the wake of an initial north/south oriented band or two of thunderstorms spreading east of the Mississippi Valley, where guidance appears suggestive that breaks in the overcast could allow insolation to contribute to at least pockets of mixed layer CAPE on the order of 1000-2000 J/kg. Of particular concern is that the environment could become conducive to at least isolated to widely scattered long lived discrete supercell development, initially anywhere from portions of eastern Missouri into Illinois, southward through portions of western Kentucky and Tennessee into northern Mississippi. In the presence of clockwise curved low-level hodographs characterized by strong to extreme shear, some of these could become capable of producing strong tornadoes. Link to comment Share on other sites More sharing options...
Drz1111 Posted April 30, 2017 Share Posted April 30, 2017 9 minutes ago, andyhb said: I was referring more to the lack of stronger ventilating flow in a very high PWAT/modest bulk shear environment, which would generally result in rapid transition to HP mode and precip-saturated RFDs. Given the intensity of the low level SRH and favorable storm relative inflow (not to mention plenty of low level instability), the latter of those conditions was essentially rendered irrelevant and the results were strong/violent tornadoes. FWIW, this doesn't really come across in the chaser videos but all the tornadoes this afternoon were substantially rainwrapped. But it seemed that even the rain-cooled air was either buoyant or near-buoyant; we were under the meso for the (much weaker) tornado immediately preceding the big wedge and while there was no wall, you could see tendrils of scud extending almost all the way to the surface being pulled almost directly into the cloud base, while rapidly moving from left to right. It was most impressive. Link to comment Share on other sites More sharing options...
arlwx Posted April 30, 2017 Share Posted April 30, 2017 Tornado Warning LAC067-083-123-301030- /O.NEW.KJAN.TO.W.0050.170430T0934Z-170430T1030Z/ BULLETIN - EAS ACTIVATION REQUESTED Tornado Warning National Weather Service Jackson MS 434 AM CDT SUN APR 30 2017 The National Weather Service in Jackson has issued a * Tornado Warning for... Morehouse Parish in northeastern Louisiana... Northwestern Richland Parish in northeastern Louisiana... West Carroll Parish in northeastern Louisiana... * Until 530 AM CDT * At 433 AM CDT, a severe thunderstorm capable of producing a tornado was located over Swartz, moving northeast at 45 mph. HAZARD...Tornado and quarter size hail. SOURCE...Radar indicated rotation. IMPACT...Flying debris will be dangerous to those caught without shelter. Mobile homes will be damaged or destroyed. Damage to roofs, windows, and vehicles will occur. Tree damage is likely. * This dangerous storm will be near... Galion around 505 AM CDT. Goodwill around 510 AM CDT. Jones around 520 AM CDT. Other locations impacted by this tornadic thunderstorm include Forest, Bonita, Collinston, Mer Rouge, Pioneer and Oak Ridge. PRECAUTIONARY/PREPAREDNESS ACTIONS... TAKE COVER NOW! Move to a basement or an interior room on the lowest floor of a sturdy building. Avoid windows. If you are outdoors, in a mobile home, or in a vehicle, move to the closest substantial shelter and protect yourself from flying debris. && LAT...LON 3271 9201 3301 9170 3301 9141 3293 9130 3288 9131 3287 9132 3287 9134 3284 9135 3275 9135 3244 9194 3246 9194 3252 9190 3260 9193 3266 9191 3267 9193 3266 9194 3271 9197 TIME...MOT...LOC 0933Z 225DEG 37KT 3257 9194 TORNADO...RADAR INDICATED HAIL...1.00IN $$ NF Link to comment Share on other sites More sharing options...
olafminesaw Posted April 30, 2017 Share Posted April 30, 2017 Canton was just barely spared the worst. Link to comment Share on other sites More sharing options...
MattPetrulli Posted April 30, 2017 Share Posted April 30, 2017 In my opinion, lets just keep this forum for the entire event because there is NO ONE discussing it in the SE forum Also debris ball going through Vicksburg, MS. Link to comment Share on other sites More sharing options...
mob1 Posted April 30, 2017 Share Posted April 30, 2017 8 minutes ago, MattPetrulli said: In my opinion, lets just keep this forum for the entire event because there is NO ONE discussing it in the SE forum Also debris ball going through Vicksburg, MS. Rotation on this one not too shabby either Link to comment Share on other sites More sharing options...
MattPetrulli Posted April 30, 2017 Share Posted April 30, 2017 So we've had about 3 tornadoes the last 15 minutes in MS... Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 In my opinion, lets just keep this forum for the entire event because there is NO ONE discussing it in the SE forum Also debris ball going through Vicksburg, MS.Nope, if it doesn't involve NC, SC or GA, they could care less about it over there usually. Link to comment Share on other sites More sharing options...
MattPetrulli Posted April 30, 2017 Share Posted April 30, 2017 Just now, SmokeEater said: Nope, if it doesn't involve NC, SC or GA, they could care less about it over there usually. I once asked about the severe threat there (right before January 21-22) and why no one was covering it. They all said they wanted snow and lived in the carolinas. Quite annoying. Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 Confirmed large and extremely dangerous tornado south of Vicksburg, moving NE. Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 I once asked about the severe threat there (right before January 21-22) and why no one was covering it. They all said they wanted snow and lived in the carolinas. Quite annoying. Lol and most of the time don't care about severe in general. Snow year round though. Link to comment Share on other sites More sharing options...
MattPetrulli Posted April 30, 2017 Share Posted April 30, 2017 Just now, SmokeEater said: Lol and most of the time don't care about severe in general. Snow year round though. Yeah they're like SE snow weenies. Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 Definite TDS from Port Gibson to the NE, it went right over town. Not good. Link to comment Share on other sites More sharing options...
downeastnc Posted April 30, 2017 Share Posted April 30, 2017 28 minutes ago, MattPetrulli said: In my opinion, lets just keep this forum for the entire event because there is NO ONE discussing it in the SE forum Also debris ball going through Vicksburg, MS. MS and AL usually are in here or Tennessee forum if they have a thread.....like Smoke said 95% of the SE forum posters live in NC/SC/GA and southern VA and most are not severe weather folks though there are a few of us but we usually end up in here. Also its like not even 9 am on a Sunday so there not a lot of traffic on the board in general. There was a pretty obvious TDS with CC on that line south of Vicksburg Link to comment Share on other sites More sharing options...
mob1 Posted April 30, 2017 Share Posted April 30, 2017 4 minutes ago, downeastnc said: MS and AL usually are in here or Tennessee forum if they have a thread.....like Smoke said 95% of the SE forum posters live in NC/SC/GA and southern VA and most are not severe weather folks though there are a few of us but we usually end up in here. Also its like not even 9 am on a Sunday so there not a lot of traffic on the board in general. There was a pretty obvious TDS with CC on that line south of Vicksburg I don't know how many frames you can go back on radar scope, but the debris signature was pretty evident for at least 16 scans. Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 Bunch of TW's near Baton Rouge now too. Link to comment Share on other sites More sharing options...
downeastnc Posted April 30, 2017 Share Posted April 30, 2017 Just now, mob1 said: I don't know how many frames you can go back on radar scope, but the debris signature was pretty evident for at least 16 scans. Yeah I saw it, is there a way to screenshot or to freeze previous images in a loop on radarscope? I just took a screenshot of the latest CC scan as I dont know how to capture any previous to that. Link to comment Share on other sites More sharing options...
SmokeEater Posted April 30, 2017 Share Posted April 30, 2017 I don't know how many frames you can go back on radar scope, but the debris signature was pretty evident for at least 16 scans. Oh yea, it first started right on top of Port Gibson, there's a tornado report from there with trees down. Link to comment Share on other sites More sharing options...
mob1 Posted April 30, 2017 Share Posted April 30, 2017 2 minutes ago, downeastnc said: Yeah I saw it, is there a way to screenshot or to freeze previous images in a loop on radarscope? I just took a screenshot of the latest CC scan as I dont know how to capture any previous to that. I don't think you can pause a loop, I just kept taking screenshots of the loop till I had the right one (I'm just primitive that way) Link to comment Share on other sites More sharing options...
Drz1111 Posted April 30, 2017 Share Posted April 30, 2017 Nice three body scatter spike with that CC image, too. Link to comment Share on other sites More sharing options...
MattPetrulli Posted April 30, 2017 Share Posted April 30, 2017 PDS warning on the Bolton cell, TDS present. Link to comment Share on other sites More sharing options...
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