Fred Gossage Posted February 22, 2011 Share Posted February 22, 2011 Thought I would go ahead and start a thread on the second, possibly more significant severe weather threat for most of Dixie Alley... with the system coming early next week. Medium range models show a powerful system with a rich Gulf flow... but there are questions. The GFS doesn't show much instability in its raw output... but the synoptic things that would be there for bigger instability... like a morning cap and EML, cool mid-level temps, etc.... are there. It should be noted that the 12Z Euro is substantially warmer than the GFS through the whole warm sector... with areas almost to Evansville, IN reaching 70F, definitely as far north as Paducah, KY.... 75F to Dyersburg and almost Nashville... and 80F+ to Jackson, MS... but with the same dynamics and dewpoints as the GFS. FWIW, the 18Z DGEX also strongly backs up the surface temperatures that the 12Z ECMWF depicts. Take this into account, and modify the GFS soundings with those Euro sfc temps.... and you get a large, wide, moderate to significantly unstable warm sector... with a large area of MS/TN/AL having SBCAPE of 1000-1500+ and LIs of -4 to -6. Obviously, this is a week out... and many questions remain unanswered... and will remain unanswered for a few more days at least... but between Thursday and this one next week... this one looks more significant for most of the Dixie Alley states. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 22, 2011 Share Posted February 22, 2011 I glanced at the 12Z Euro--the 168-192 wave is much beefier and farther S than the GFS--and would be a much bigger threat no doubt. Potentially significant verbatim. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 22, 2011 Share Posted February 22, 2011 Handy quick look I use, off ECMWF site. Plenty of low level jet over Dixie Mid level divergence and implied shear... PSU e-Wall with RH shown. This looks, per Euro, potentially major. Link to comment Share on other sites More sharing options...
Reed Stough Posted February 22, 2011 Share Posted February 22, 2011 Yeah - this one looks more interesting than the one for Thursday. Link to comment Share on other sites More sharing options...
CUmet Posted February 22, 2011 Share Posted February 22, 2011 I've had my eye on this one as well, and agree that this has a higher ceiling. I too am a bit perplexed at the low instability fields being progged by the GFS, even considering it's low long-range bias in the past. Many of the soundings in the warm sector possess a well-defined elevated mixed layer (even on the 00z ECMWF's bowling-ball solution). And the areal coverage of the 60F dewpoints progged is massive for an early-season severe event. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 22, 2011 Share Posted February 22, 2011 Sunday is showing some potential on the 0z GFS but haven't looked at much for this day. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 22, 2011 Share Posted February 22, 2011 That is an impressive low on the 0Z Euro. Hour 162 1000-500 mb heights are below 540 dm over Central Texas. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 22, 2011 Share Posted February 22, 2011 12Z GFS is a lot faster than the Euro, and seems to like Eastern Oklahoma and Arkansas... Hint of a warm/dry nose on the FSM sounding then around 750 mb, but its subtle, and might prevent premature detonation. Excellent mid level instability and pretty good shear. Of course,a forecast skew-T for 5 days away, especially when there appears to be timing issues between the GFS and Euro, is for entertainment purposes only. Link to comment Share on other sites More sharing options...
thewxmann Posted February 22, 2011 Share Posted February 22, 2011 The breadth and quality of the warm sector progged for this setup is ridiculous for February, that's all I got to say. Link to comment Share on other sites More sharing options...
tornadotony Posted February 22, 2011 Share Posted February 22, 2011 The Euro has a very 1/21/99-like quality to it...the very deep, closed upper low and the gigantic and ridiculously high-quality warm sector...geez. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 22, 2011 Share Posted February 22, 2011 The Euro has a very 1/21/99-like quality to it...the very deep, closed upper low and the gigantic and ridiculously high-quality warm sector...geez. Made me Google... http://www.targetarea.net/jan21.html Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 Quite simply put, the 12Z run of the Euro is a high impact severe weather event Monday across AR/LA/KY/TN/MS/AL. Tornadoes would be a good bit over a very large area. This run has Nashville hitting 75-77F Monday afternoon... BHM and TCL hitting 80F... with widespread 65+ dewpoints and a well-defined, widespread elevated mixed layer. Link to comment Share on other sites More sharing options...
Indystorm Posted February 23, 2011 Share Posted February 23, 2011 Tonight's 00z GFS develops an absolute bomb cutting through the Midwest Sunday night into Monday. Insane 300 mb jet and 500 mb trough. I honestly don't know what to make of this especially since the previous Feb. 24-25 storm rides eastward nonchalantly. Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 We seem to be getting better agreement with time between the GFS and ECMWF... in terms of a very dynamic system... with a rapidly deepening low pressure that tracks into the Ohio Valley.... with a large, wide warm sector. However, the GFS is still 12-18 hours faster than the ECMWF. I can't help but remember past events a few years ago where the GFS would have the same synoptic setup as the Euro.... but be up to a day faster.... only to trend slower toward the Euro... once we get within 48-72 hours of the event. Only mentioning it since the CIPS system from SLU has it as a top 500-mb analog... but Super Tuesday is one such example. Link to comment Share on other sites More sharing options...
CUmet Posted February 23, 2011 Share Posted February 23, 2011 We seem to be getting better agreement with time between the GFS and ECMWF... in terms of a very dynamic system... with a rapidly deepening low pressure that tracks into the Ohio Valley.... with a large, wide warm sector. However, the GFS is still 12-18 hours faster than the ECMWF. I can't help but remember past events a few years ago where the GFS would have the same synoptic setup as the Euro.... but be up to a day faster.... only to trend slower toward the Euro... once we get within 48-72 hours of the event. Only mentioning it since the CIPS system from SLU has it as a top 500-mb analog... but Super Tuesday is one such example. What are your thoughts regarding whether this trough might be too dynamic and amplified for a large-scale tornado outbreak? If you gave me just the 500 mb chart, I would say it is too amplified. However, looking at the huge mid-level dry punch through the warm sector in the morning hours and the numerous forecast soundings showing a well-defined elevated mixed layer, this one could be different. Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 What are your thoughts regarding whether this trough might be too dynamic and amplified for a large-scale tornado outbreak? If you gave me just the 500 mb chart, I would say it is too amplified. However, looking at the huge mid-level dry punch through the warm sector in the morning hours and the numerous forecast soundings showing a well-defined elevated mixed layer, this one could be different. The 00Z GFS is a little sharp, definitely. However.... the Euro isn't quite as intensely sharp... especially when you start looking at vertical velocities and the low amplitude nature of the actual isotachs. When you go back and look at March 1, 1997... the actual wind barbs are of a lot lower amplitude than the curve of the height contours within the middle of the trough.... and with the Euro, at least... that may be the case here too. Then... with the GFS and ECMWF.... there's also the large EML plume across the warm sector.... It would be more doable with this trough... than with a lot of other events with sharp troughs. I think the biggest question with this whole setup is the timing of the system. My initial thoughts right now... watch for the GFS to slow down in coming days. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted February 23, 2011 Share Posted February 23, 2011 pretty big difference between the 0z and 12z runs of the GFS, on the new run were getting a small northern stream vort to come down out of Canada and phase with the the southern stream system. You can clearly see it between 66-78hr. On the 12z run it completely misses the northern vort and brings it across the upper MW while the southern wave hangs back in southern california. This phasing speeds it up /makes it more progessive and not slower like the 12z run has it. This new run would be big severe weather maker with the huge warm sector and rapidly deepening low, going to be very interesting to see how this plays out for sure. The 12z Euro looks like its even slower and not having a phase like the new GFS. Link to comment Share on other sites More sharing options...
mnweather Posted February 23, 2011 Share Posted February 23, 2011 pretty big difference between the 0z and 12z runs of the GFS, on the new run were getting a small northern stream vort to come down out of Canada and phase with the the southern stream system. You can clearly see it between 66-78hr. On the 12z run it completely misses the northern vort and brings it across the upper MW while the southern wave hangs back in southern california. This phasing speeds it up /makes it more progessive and not slower like the 12z run has it. This new run would be big severe weather maker with the huge warm sector and rapidly deepening low, going to be very interesting to see how this plays out for sure. The 12z Euro looks like its even slower and not having a phase like the new GFS. Could that be a case of the Euro holding back energy in the Southwest? Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 00Z Euro is faster. 00Z GFS is faster. All of today's GFS ensembles were faster than the op GFS and Euro. They would have you believe it's a Sunday afternoon/night threat on I-65.... with the same kind of parameters... just 24 hours sooner than the 12Z Euro. Still a lot of details to look out. Regardless.... a dynamic system with a wide, high quality warm sector AND elevated mixed layer plume.... looks like a good bet. Timing is the big question mark. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 23, 2011 Share Posted February 23, 2011 IMBY, the 20ºC on the Euro Sunday late afternoon strongly suggests capped, as does the positive tilt. The quick look, 60 knot 850 mb jet looks dangerous to me. Not sure on directional shear being super high as Euro getting toward stacked. Hard to tell from the Euro, but it sort of looks like it is suggesting a squall line, maybe with embedded supercells, and I wouldn't be surprised if the most active severe was before peak heating between these two 24 hour snapshots. Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 Quite honestly, after looking at all the evening guidance... even that faster Euro above may be too slow. EVERYTHING sped up tonight. GFS, GFS ensembles, Euro, Canadian, UKMET, NOGAPS, even the Japanese model. With the exception of the op GFS and Euro... that MAY be playing catch-up... this MIGHT end up being a Sunday afternoon/night event for TN/MS/AL... as opposed to the earlier thinking of Monday. It's usually not wise to make wholesale changes this far ahead of time, but you can't ignore it when EVERY scrap of guidance in the solar system does the same exact thing (and on a major run time.... not an 18Z or 6Z). Having said this.... even with an earlier timing... it's still a significant event. Ed, as for the positive tilt concern and possibly being more favorable for a squall line event.... I urge you to look for a thread I wrote a little while back in this sub-forum about violent tornado outbreaks by trough tilt for Alabama. Some of our most violent tornado outbreaks in this state's history.... have happened with positive tilt troughs. Link to comment Share on other sites More sharing options...
Hoosier Posted February 23, 2011 Share Posted February 23, 2011 Haven't looked at this one too closely yet (been spending most of my time on the first event) but I could see some severe threat getting this far north depending on low track and timing. Certainly looks to have huge *potential* for the deep south into the OV. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 23, 2011 Share Posted February 23, 2011 GFS suggests some potential Sunday afternoon Eastern OK/MO/AR... Link to comment Share on other sites More sharing options...
CUmet Posted February 23, 2011 Share Posted February 23, 2011 Quite honestly, after looking at all the evening guidance... even that faster Euro above may be too slow. EVERYTHING sped up tonight. GFS, GFS ensembles, Euro, Canadian, UKMET, NOGAPS, even the Japanese model. With the exception of the op GFS and Euro... that MAY be playing catch-up... this MIGHT end up being a Sunday afternoon/night event for TN/MS/AL... as opposed to the earlier thinking of Monday. It's usually not wise to make wholesale changes this far ahead of time, but you can't ignore it when EVERY scrap of guidance in the solar system does the same exact thing (and on a major run time.... not an 18Z or 6Z). Having said this.... even with an earlier timing... it's still a significant event. Ed, as for the positive tilt concern and possibly being more favorable for a squall line event.... I urge you to look for a thread I wrote a little while back in this sub-forum about violent tornado outbreaks by trough tilt for Alabama. Some of our most violent tornado outbreaks in this state's history.... have happened with positive tilt troughs. It's interesting to see that the Euro is keeping this pretty positively-tilted until at least Monday morning. This really helps ensure sufficient directional shear over the warm sector for the Sunday evening/overnight event. Also, with this kind of orientation, forcing for vertical motion is more diffuse. The Euro remains slightly slower than the GFS and UKMET. It's pretty clear that the main event will be from Sunday afternoon to Monday morning, and it continues to look like a high-impact event. Link to comment Share on other sites More sharing options...
Hoosier Posted February 23, 2011 Share Posted February 23, 2011 Title edited to include the OV for this potential threat. Link to comment Share on other sites More sharing options...
Stebo Posted February 23, 2011 Share Posted February 23, 2011 Title edited to include the OV for this potential threat. Link to comment Share on other sites More sharing options...
Fred Gossage Posted February 23, 2011 Author Share Posted February 23, 2011 Sone of the analogs coming from the CIPS Winter Analog guidance at St. Louis University on the past couple of runs.... are interesting to say the least. We have 2/5/08, 11/27/94, 1/21/99, 3/1/97, 3/1/07, 1/10/08, 11/24/01... 2/5/08 showed up on two different perturbations (kinda like individual ensemble members) toward the upper part of the list... and one of those.... it made it to the top of the list. It's interesting to note that ALL of those included F3-F4 damage. Link to comment Share on other sites More sharing options...
Stebo Posted February 23, 2011 Share Posted February 23, 2011 Sone of the analogs coming from the CIPS Winter Analog guidance at St. Louis University on the past couple of runs.... are interesting to say the least. We have 2/5/08, 11/27/94, 1/21/99, 3/1/97, 3/1/07, 1/10/08, 11/24/01... 2/5/08 showed up on two different perturbations (kinda like individual ensemble members) toward the upper part of the list... and one of those.... it made it to the top of the list. It's interesting to note that ALL of those included F3-F4 damage. Yeah I recognize some of those dates immediately Link to comment Share on other sites More sharing options...
Macintosh Posted February 23, 2011 Share Posted February 23, 2011 Title edited to include the OV for this potential threat. Can I come? Link to comment Share on other sites More sharing options...
Kevin Askew Posted February 23, 2011 Share Posted February 23, 2011 Can I come? we like chasing in that area and AR. Msg me if interested, we are in Marion IL. Link to comment Share on other sites More sharing options...
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