CUmet Posted February 27, 2011 Share Posted February 27, 2011 I would tend to agree with Jim on this. My rule of thumb is typically sfc-500 mb wind direction difference of 45 degrees...anything above that is fine for sustained supercells, but below that it gets a lot more difficult. Not to mention the veer-back-veer pattern as you go up with height. Link to comment Share on other sites More sharing options...
thewxmann Posted February 27, 2011 Share Posted February 27, 2011 ^@Tony: I'm mostly referring to after 06Z, with the 2nd round of storms. I'm decently gung-ho on the first round since the sfc low reformation wouldn't be making a huge dent on the surface windfield until after then. That SSW wind is doable, but again taken verbatim, it's still not as potent as a more backed flow, which is needed to up the ceiling on this event to stronger levels. Depending on many mesoscale factors the surface flow could still go either way. Link to comment Share on other sites More sharing options...
cmichweather Posted February 27, 2011 Share Posted February 27, 2011 The sfc flow on the GFS is SW in many areas...behind the convection. Let's try looking just ahead of it... Large, looping hodo in SSW sfc flow...this is NE AR at 06z... nice looking profile, but this isn't a very alarming or crazy profile. Your 500-700 you'd like to see straight westerly flow and the problem I see with the surface flow along with not being SE is it is weak. I still think we have a decent outbreak but the Hodo's out of the region are ok, we'll probably end up similar to the recent event probably 20 tornadoes. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 I would tend to agree with Jim on this. My rule of thumb is typically sfc-500 mb wind direction difference of 45 degrees...anything above that is fine for sustained supercells, but below that it gets a lot more difficult. Not to mention the veer-back-veer pattern as you go up with height. We have 45 degrees especially on the NAM. The veer-back-veer thing is interesting and could be an issue, but it doesn't seem to be that pronounced imo and a fairly minor change would basically eradicate that. Link to comment Share on other sites More sharing options...
tornadotony Posted February 27, 2011 Share Posted February 27, 2011 The other thing to keep in mind is the GFS's propensity of late to be too weak (even outside its scaling differences from the NAM and other mesoscale models) with sfc reflections of recent storms. My suspicion is that's the case with this one, and that the NAM's intensity of the sfc reflection is far more likely to win over the GFS's. Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2011 Share Posted February 27, 2011 nice looking profile, but this isn't a very alarming or crazy profile. Your 500-700 you'd like to see straight westerly flow and the problem I see with the surface flow along with not being SE is it is weak. I still think we have a decent outbreak but the Hodo's out of the region are ok, we'll probably end up similar to the recent event probably 20 tornadoes. I could agree with this, but being that it looks like mostly a night time event, it just takes one tornado to make this significant. Link to comment Share on other sites More sharing options...
earthlight Posted February 27, 2011 Share Posted February 27, 2011 One more look at the Day 1...for Hoosier Link to comment Share on other sites More sharing options...
CUmet Posted February 27, 2011 Share Posted February 27, 2011 We have 45 degrees especially on the NAM. The veer-back-veer thing is interesting and could be an issue, but it doesn't seem to be that pronounced imo and a fairly minor change would basically eradicate that. No we don't, at least not west of the MS river at 06z. I've looked everywhere on the NAM in AR/MO at that time, and it gets close in some places (40 degrees or so), but never above 45. The GFS is worse. Now of course that's taking it verbatim, and it's not all that far away from being sufficient for sustained supercells, which is why if it were a slightly different trough/sfc low evolution, things would be much different. The best chance for significant tornadoes I think is anything that fires in the relatively-backed low-level flow S or SE of the lead wave that heads up into IL/IN by 06z. Link to comment Share on other sites More sharing options...
Hoosier Posted February 27, 2011 Share Posted February 27, 2011 No we don't, at least not west of the MS river at 06z. I've looked everywhere on the NAM in AR/MO at that time, and it gets close in some places (40 degrees or so), but never above 45. The GFS is worse. Now of course that's taking it verbatim, and it's not all that far away from being sufficient for sustained supercells, which is why if it were a slightly different trough/sfc low evolution, things would be much different. The best chance for significant tornadoes I think is anything that fires in the relatively-backed low-level flow S or SE of the lead wave that heads up into IL/IN by 06z. Gotcha...I was mainly looking along/east of the river. Link to comment Share on other sites More sharing options...
ksstormhunter Posted February 27, 2011 Share Posted February 27, 2011 Just looking at my latest output and still staying pretty consistent with a target area of Chanute-Pittsburg-Coffeyville, KS, to Joplin, MO to Miami, OK-Neosho, OK. Time frame for this is still looking around 02-05Z, but that keeps waffling back and forth, hoping to get a good time down in the morning. Any thoughts on potential for this area. Graphic map is viewable at http://smartwxmodel.net. Link to comment Share on other sites More sharing options...
CarbondaleWX Posted February 27, 2011 Share Posted February 27, 2011 Tornado: Hail: Wind: Link to comment Share on other sites More sharing options...
cmichweather Posted February 27, 2011 Share Posted February 27, 2011 I could agree with this, but being that it looks like mostly a night time event, it just takes one tornado to make this significant. Ya I know... it only takes one. Just that 0-3km shear isn't impressive to me. I see this very similar to the other days event squall line with embedded rotation and tornado threat. Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2011 Share Posted February 27, 2011 Ya I know... it only takes one. Just that 0-3km shear isn't impressive to me. I see this very similar to the other days event squall line with embedded rotation and tornado threat. Mike what area/time you looking at, I am mostly focusing on 0z and especially 6z east of the Mississippi River and North of Memphis. Link to comment Share on other sites More sharing options...
cmichweather Posted February 27, 2011 Share Posted February 27, 2011 Mike what area/time you looking at, I am mostly focusing on 0z and especially 6z east of the Mississippi River and North of Memphis. if I had to pick it'd right along the OK/MS/AR area seems like it'd be the best area to catch a tornadic storm before it went linear Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2011 Share Posted February 27, 2011 if I had to pick it'd right along the OK/MS/AR area seems like it'd be the best area to catch a tornadic storm before it went linear Yeah see I am looking more at the warm/moisture frontal area, back there things would be less conducive for tornadoes. Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 27, 2011 Author Share Posted February 27, 2011 In my experience in dealing with Dixie Alley tornado outbreaks... the veering on these hodographs being discussed... in the lowest 2 kilometers... is more than adequate for not only strong tornadoes... but violent, long-tracked tornadoes. I can cite enough historical cases to make you all shut up and never talk to me again for the rest of your lives. HOWEVER, I will also say that... with the veer-back-veer pattern in the mid-levels as significant as it is... I have busted many a significant tornado forecast in both Dixie Alley and Tornado Alley with that pattern. It's not so much a direct problem for tornadogenesis as it is... a problem for supercell storm mode.... that trickles down to a problem for significant tornadogenesis. Even with an EML and forcing more favorable for discrete mode... with such a mid-level wind profile... I could easily see these storms lining out much faster than they otherwise would tomorrow night. Having said that, I still would've hatched the tornado probabilities on the Day 1.... Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 27, 2011 Share Posted February 27, 2011 TOR probs increasesd as well as hatched area also three rounds/area to watch possible DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0653 AM CST SUN FEB 27 2011 VALID 271300Z - 281200Z ..THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF AR SERN MO...WRN PARTS OF TN AND KY...SRN IL AND FAR SWRN IND... ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE CNTRL/SRN PLAINS NEWD THROUGH MUCH OF THE OH VALLEY... ..SYNOPSIS MID AND UPPER-LEVEL CYCLONE OVER THE LOWER CO VALLEY WILL BECOME INCREASINGLY SHEARED WHILE TRANSLATING EWD INTO CONFLUENT FLOW REGIME IN PLACE E OF THE ROCKIES. THE LEADING PORTION OF THIS SYSTEM IS FORECAST TO REACH THE CNTRL/SRN HIGH PLAINS BY AFTERNOON PRIOR TO LOSING AMPLITUDE WHILE EJECTING NEWD INTO THE UPPER MIDWEST OVERNIGHT. IN ITS WAKE...THE MORE SUBSTANTIAL...REMAINING PORTION OF MIDLEVEL TROUGH WILL SHIFT EWD THROUGH THE CNTRL/SRN PLAINS TOWARD THE MID/LOWER MS VALLEYS BY 28/12Z. AT THE SURFACE...LEE CYCLONE NOW DEEPENING OVER ERN CO IS FORECAST TO DEVELOP TO THE VICINITY OF THE OK/KS BORDER NEAR OR JUST W OF I-35 BY 28/00Z BEFORE ACCELERATING NEWD THROUGH CNTRL MO AND THE OH VALLEY TONIGHT. AN ASSOCIATED WARM FRONT WILL LIFT NWD THROUGH THE OZARKS AND MID MS/OH VALLEYS IN ADVANCE OF THIS INITIAL SURFACE LOW WHILE A TRAILING COLD FRONT PUSHES SEWD THROUGH THE SRN PLAINS. ELSEWHERE...A DRYLINE WILL MIX EWD TO THE VICINITY OF I-35 IN OK/N TX BY LATE AFTERNOON BEFORE BEING OVERTAKEN BY PACIFIC FRONT WHICH WILL SURGE EWD TOWARD THE LOWER MS VALLEY IN TANDEM WITH PRIMARY PORTION OF UPPER TROUGH. THERE IS SOME INDICATION THAT A SECONDARY SURFACE LOW MAY FORM TONIGHT AT THE INTERSECTION OF THE COLD AND PACIFIC FRONTS NEAR THE CONFLUENCE OF THE MS AND OH VALLEYS. ..CNTRL/SRN PLAINS INTO THE OH VALLEY AND MID-SOUTH LATEST MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE HAS TRENDED TOWARD A HIGHER PROBABILITY OF DIURNAL TSTM DEVELOPMENT THIS AFTERNOON INTO EVENING FROM THE VICINITY OF SURFACE TRIPLE POINT OVER S-CNTRL KS/N-CNTRL OK NEWD TOWARD MKC. HERE...DEEP ASCENT IN EXIT REGION OF UPPER JET STREAK /ATTENDANT TO LEAD IMPULSE MENTIONED ABOVE/ COUPLED WITH A STRENGTHENING FRONTOGENETICAL CIRCULATION ARE EXPECTED TO OVERCOME CAP...SUPPORTING TSTM DEVELOPMENT ALONG OR ON IMMEDIATE COOL SIDE OF SURFACE BOUNDARY. STEEP MIDLEVEL LAPSE RATES AND BOUNDARY LAYER DEW POINTS IN THE UPPER 50S TO LOWER 60S WILL YIELD A MODERATELY UNSTABLE ENVIRONMENT WITH MLCAPE VALUES APPROACHING 1000 J/KG. MOREOVER...LOCALLY BACKED NEAR-SURFACE WINDS BENEATH SWLY MIDLEVEL FLOW INCREASING TO 80-90 KT WILL RESULT IN MORE THAN SUFFICIENT VERTICAL SHEAR FOR ORGANIZED STORMS INCLUDING SUPERCELLS. THE PRIMARY HAZARD APPEARS TO BE HAIL...THOUGH A TORNADO OR TWO IS POSSIBLE WITH ANY STORMS ROOTED IN THE BOUNDARY LAYER. EXPECT A RAPID DOWNSTREAM EXPANSION IN STRONG TO SEVERE TSTMS TONIGHT FROM THE MID MS VALLEY EWD THROUGH THE OH VALLEY ALONG AND S OF WARM FRONT AND IN ADVANCE OF MIGRATORY SURFACE LOW. AMBIENT ENVIRONMENT WILL BE CHARACTERIZED BY MARGINAL INSTABILITY /I.E. MLCAPE VALUES GENERALLY LESS THAN 500 J PER KG/ BUT VERY STRONG LOW AND DEEP-LAYER SHEAR. AS SUCH...THE POTENTIAL WILL EXIST FOR FAST-MOVING SUPERCELL AND/OR BOWING STORM CLUSTERS WITH A THREAT FOR DAMAGING WINDS AND TORNADOES. A SECOND...POTENTIALLY HIGHER IMPACT TSTM REGIME MAY DEVELOP LATE THIS AFTERNOON OR MID/LATE EVENING FROM PORTIONS OF CNTRL/NERN AR NEWD INTO THE LOWER OH VALLEY...ALONG RETREATING WARM FRONT OR PERHAPS IN THE WAKE OF THE FRONT ALONG A CONFLUENCE ZONE DEVELOPING WITHIN THE OPEN WARM SECTOR. HERE...SEVERAL MESOSCALE AND CONVECTION-ALLOWING MODELS DEVELOP A DISTINCTLY SEPARATE AREA OF CONVECTIVE PRECIPITATION WHICH EVENTUALLY MERGES WITH ABOVE-MENTIONED CORRIDOR OF STORMS TRAVERSING THE OH VALLEY. GIVEN THE MOIST/LOW LCL ENVIRONMENT...STRONG VERTICAL SHEAR AND POTENTIAL FOR A MORE DISCRETE STORM MODE...IT APPEARS THAT THIS SETUP WOULD FOSTER THE GREATEST THREAT FOR SIGNIFICANT TORNADOES IN ADDITION TO HAIL AND LOCALLY DAMAGING WIND GUSTS. A THIRD SVR TSTM EPISODE IS EXPECTED TO TAKE SHAPE ACROSS PARTS OF ERN OK/WRN AR THIS EVENING INTO TONIGHT AS A PACIFIC FRONT OVERTAKES THE DRYLINE AND SURGES EWD IN CONCERT WITH THE MAIN PORTION OF THE UPPER TROUGH. INITIAL STORM MODE MAY BE SUPERCELLULAR...THOUGH A RAPID TRANSITION TO QLCS IS EXPECTED WITH THE CONVECTIVE SYSTEM REACHING WRN TN AND THE MS DELTA REGION BY THE END OF THE D1 PERIOD. HERE TOO...VERTICAL SHEAR WILL BE QUITE STRONG AND SUPPORTIVE OF EMBEDDED SUPERCELL AND/OR BOWING STRUCTURES CAPABLE OF POTENTIALLY WIDESPREAD DAMAGING WINDS AND A FEW TORNADOES. Link to comment Share on other sites More sharing options...
Indystorm Posted February 27, 2011 Share Posted February 27, 2011 Stay safe down your way, Beau. That is a really complex SPC outlook this morning with three separate possible waves of svr t storms with this oncoming system. 10% hatched tornado potential now all the way ne to Terre Haute. Link to comment Share on other sites More sharing options...
blackjack123 Posted February 27, 2011 Share Posted February 27, 2011 I have a question. Is there any difference between a strong and a significant tornado. A strong tornado is anything EF2+ so is a significant tornado anything EF3+ or is it the same as a strong tornado. EF2(Significant), EF3(Severe), EF4(Devastating), and EF5(Incredible). Link to comment Share on other sites More sharing options...
Indystorm Posted February 27, 2011 Share Posted February 27, 2011 I have a question. Is there any difference between a strong and a significant tornado. A strong tornado is anything EF2+ so is a significant tornado anything EF3+ or is it the same as a strong tornado. EF2(Significant), EF3(Severe), EF4(Devastating), and EF5(Incredible). I've always thought that strong/significant tornadoes are EF 2 and EF 3 with the word Violent used for EF-4 and EF 5. Link to comment Share on other sites More sharing options...
janetjanet998 Posted February 27, 2011 Share Posted February 27, 2011 Hmm high res pops some supercells this afternoon/evening over northeast AR so does the 12z NAM in fact very ominous for your region with rounds fo severe storms ..more unstable a low end HIGH risk may be needed due to the multiple rounds increasing the odds of a severe event Link to comment Share on other sites More sharing options...
IWXwx Posted February 27, 2011 Share Posted February 27, 2011 One more look at the Day 1...for Hoosier Sorry for the kind of OT question, but where do you find that convective outlook map overlayed on the county map? Link to comment Share on other sites More sharing options...
Stebo Posted February 27, 2011 Share Posted February 27, 2011 Well I see they went 15% with a hatched area. Certainly could get very rough down that way by Beau, back SW to Little Rock. Really a bit worrisome due to the fact that this could very well be mostly if not all a nighttime event. Link to comment Share on other sites More sharing options...
hoosierwx Posted February 27, 2011 Share Posted February 27, 2011 Bright sunshine has broken out here, might add to instability for the warm frontal passage later this morning. Link to comment Share on other sites More sharing options...
Indystorm Posted February 27, 2011 Share Posted February 27, 2011 Bright sunshine has broken out here, might add to instability for the warm frontal passage later this morning. Yes, present satellite shows pockets of clearing popping up throughout the mid south. If this continues it will only increase the threat. Link to comment Share on other sites More sharing options...
David Reimer Posted February 27, 2011 Share Posted February 27, 2011 The 12Z and 13Z RUC are both very similar in depicting convection firing along the OK/KS border near I-35 by 22Z with considerable instability present. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 27, 2011 Share Posted February 27, 2011 The 12Z and 13Z RUC are both very similar in depicting convection firing along the OK/KS border near I-35 by 22Z with considerable instability present. Are you setting up to reach that if it develops? Link to comment Share on other sites More sharing options...
David Reimer Posted February 27, 2011 Share Posted February 27, 2011 Are you setting up to reach that if it develops? I'll be in OKC by noon and will decide from there. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 27, 2011 Share Posted February 27, 2011 14z RUC showing CAPE values near 2500 j/kg in OK this evening.. I wouldn't be shocked if he see a high risk in later outlooks. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 27, 2011 Share Posted February 27, 2011 I don't see it happening but IF something can go up in the triple point at this time....look out. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.