QVectorman Posted February 29, 2012 Share Posted February 29, 2012 This is only a snapshot at one location (Indianapolis) but it shows the model differences. NAM still has a favorable environment for severe weather at 00z Saturday while the GFS has already moved the cold front through. NAM appears to keep the lift west of this by a 100 miles or so and slated to arrive 3 hrs after that. At this time based on the 12z NAM I would venture to say by the time the lift or squall line developed/arrived in Indy that environment will be long gone unfortunately. One of the best profiles I've seen in the past year though and certainly the best sounding over the GLOV. Very very conducive to tornadoes IF a storm were to enter that environment. Link to comment Share on other sites More sharing options...
wxsmwhrms Posted February 29, 2012 Share Posted February 29, 2012 I was referring to the 0z. 12z GFS is has transferred best lift east of the best thermodynamics and shear in those areas. But there are a few areas they overlap so I would expect some decent wx over cn. tenn and n. miss. based on this prog. Wait a minute, I am confused. Now are you saying that rather than lagging the system the best lift is too far EAST of the better thermondynamics/shear? Because I am not seeing that... Link to comment Share on other sites More sharing options...
Hoosier Posted February 29, 2012 Share Posted February 29, 2012 NAM appears to keep the lift west of this by a 100 miles or so and slated to arrive 3 hrs after that. At this time based on the 12z NAM I would venture to say by the time the lift or squall line developed/arrived in Indy that environment will be long gone unfortunately. One of the best profiles I've seen in the past year though and certainly the best sounding over the GLOV. Very very conducive to tornadoes IF a storm were to enter that environment. The low level flow is veering around/just after that time but I'd have to think there would at least be a significant damaging wind threat given the very strong wind fields and possibly a QLCS tor threat. FWIW, sounds like HPC isn't buying the NAM soln and is going with a GFS/ECMWF compromise. Link to comment Share on other sites More sharing options...
QVectorman Posted February 29, 2012 Share Posted February 29, 2012 Wait a minute, I am confused. Now are you saying that rather than lagging the system the best lift is too far EAST of the better thermondynamics/shear? Because I am not seeing that... Look at the QPF/sfc 850/700/500 mb vv's maps one line of storms is already into eastern KY by 18z where there is hardly any CAPE or shear. At 0z it develops another line over w. KY and n. MS. Great vv's over n. MS but there's not really much shear left nor much CAPE to work with. The atmosphere is pretty worked over by then from previous convection. Link to comment Share on other sites More sharing options...
QVectorman Posted February 29, 2012 Share Posted February 29, 2012 The low level flow is veering around/just after that time but I'd have to think there would at least be a significant damaging wind threat given the very strong wind fields and possibly a QLCS tor threat. FWIW, sounds like HPC isn't buying the NAM soln and is going with a GFS/ECMWF compromise. Yup, I could certainly see wind gusts up to 50 mph based on the NAM prog. for Indy. But it's an outlier for now and the GFS is a wash over IND...nothing exciting there. The GFS has the best potential over N. MS in my opinion. Link to comment Share on other sites More sharing options...
Hoosier Posted February 29, 2012 Share Posted February 29, 2012 Yup, I could certainly see wind gusts up to 50 mph based on the NAM prog. for Indy. But it's an outlier for now and the GFS is a wash over IND...nothing exciting there. The GFS has the best potential over N. MS in my opinion. GFS could well be underdone with surface temps though, which would affect the instability output. Wouldn't be the first time in this type of setup. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted February 29, 2012 Share Posted February 29, 2012 GFS could well be underdone with surface temps though, which would affect the instability output. Wouldn't be the first time in this type of setup. Nearly every set-up for the past 2 months, the GFS has always underdone surface temps and associated instability. Link to comment Share on other sites More sharing options...
tornadotony Posted February 29, 2012 Share Posted February 29, 2012 A. I said hardly any CAPE...ie compared to the west of it and I said...the atmosphere is worked over...over N. MS... B. I haven't had time to micro analyse what exactly goes on over N. MS. I have better s&it to do. The CAPE breaks down over N. MS from 18z to 0z. something happens, I don't know, don't care. The CAPE is way less. C. The fact I'm using VV/QPF is a guidance, that's what it's there for. If you don't like the GFS in this situation use the F'n NAM then, you have a different outcome. If you think using vv/qpf is asinine then talk to Paul Markowski who taught it to me over 15 years ago at PSU. It's worked pretty well and I will put money on it that I can out forecast you any day, especially severe wx. Guidance is just that, guidance. You are instead spitting out verbatim what's going to happen based off guidance solutions of mesoscale processes 60h out. I don't care who taught you meso back 15 years ago, that's just not wise. Meso features usually have a max predictability lead time of 24h, and that's even a stretch. You have to look at the big picture. Link to comment Share on other sites More sharing options...
QVectorman Posted February 29, 2012 Share Posted February 29, 2012 Guidance is just that, guidance. You are instead spitting out verbatim what's going to happen based off guidance solutions of mesoscale processes 60h out. I don't care who taught you meso back 15 years ago, that's just not wise. Meso features usually have a max predictability lead time of 24h, and that's even a stretch. You have to look at the big picture. I agree. This isn't mesoscale...I'm looking synoptically/dynamically...why would I use the GFS on the mesoscale?? Link to comment Share on other sites More sharing options...
PatrickSumner Posted February 29, 2012 Share Posted February 29, 2012 NWS in Louisville VERY aggressive about the severe weather threat for Friday. That are hitting this one hard... ...Another Severe Weather Outbreak Possible Friday and Friday Night... Latest model data continue to indicate the strong possibility of active and hazardous weather for the Friday and Friday night period. In the synoptic view, surface low is forecast to strengthen as it moves out of Missouri and into the western Great Lakes by Friday night. As this occurs, the models show a very strong jet stream nosing around the base of a progressive positive tilt trough. The models are a bit stronger with the jet streak as it passes just northwest of the region...placing us effectively in the favorable right entrance region. At the surface, a surface warm front will likely be located just to the southwest of the region Friday morning. This front will quickly push to the north courtesy of a strong nocturnal low-level jet axis. Strong theta-E advection along with isentropic lift associated with the low-level jet will likely some elevation convection along and just ahead of the warm front. This convection could be severe with large hail some damaging winds being possible. However, the extent of severe is a bit unknown since the low-level surface air will likely remain fairly stable. After the front pushes northward...we will get warm-sectored and should see a rapid increase in both temperature and dewpoints. Secondary and more widespread severe weather outbreak looks increasingly likely Friday afternoon and evening as a very strong surface cold front pushes in from the west. The latest deterministic and ensemble wind profiles suggest a combination of strong speed and directional shear with proximity soundings showing large/curved hodographs. Bulk shear is quite impressive and supportive of strong convection capable of all severe weather modes. In general, the NAM-WRF and SREF solutions are a bit more aggressive than the GFS solutions in the instability department. Despite the anticipated cloud cover, temperatures in the low-level warm air advection scheme should allow temperatures to warm into the lower 70s. This, combined with dewpoints in the upper 50s to lower 60s should result in a decent amount of instability. Given the combination of shear profiles and instability forecast by the NAM-WRF and SREF probabilistic forecasts...a rather large regional severe outbreak seems likely. Initial mode of convection could generally be discrete cells capable of all modes of severe weather including damaging winds, hail, and tornadoes. It does appear that the directional shear will become more speed based shear which probably will result in convection becoming quasi-linear in nature as the night goes on. Link to comment Share on other sites More sharing options...
tornadotony Posted February 29, 2012 Share Posted February 29, 2012 I agree. This isn't mesoscale...I'm looking synoptically/dynamically...why would I use the GFS on the mesoscale?? No you are not. You are using VV to diagnose convection, an inherently mesoscale process. Link to comment Share on other sites More sharing options...
QVectorman Posted February 29, 2012 Share Posted February 29, 2012 No you are not. You are using VV to diagnose convection, an inherently mesoscale process. Really...I can't use VVs on a dynamic scale to judge what mesoscale process may evolve? If it's not there dynamically/synoptically...it has a lower likely hood of happen on the mesoscale. Link to comment Share on other sites More sharing options...
Hoosier Posted February 29, 2012 Share Posted February 29, 2012 A. I said hardly any CAPE...ie compared to the west of it and I said...the atmosphere is worked over...over N. MS... B. I haven't had time to micro analyse what exactly goes on over N. MS. I have better s&it to do. The CAPE breaks down over N. MS from 18z to 0z. something happens, I don't know, don't care. The CAPE is way less. C. The fact I'm using VV/QPF is a guidance, that's what it's there for. If you don't like the GFS in this situation use the F'n NAM then, you have a different outcome. If you think using vv/qpf is asinine then talk to Paul Markowski who taught it to me over 15 years ago at PSU. It's worked pretty well and I will put money on it that I can out forecast you any day, especially severe wx. We can have a good debate without these types of confrontational remarks. Link to comment Share on other sites More sharing options...
Hoosier Posted February 29, 2012 Share Posted February 29, 2012 I admit it may be a little too early to say this but looking at the big picture, with a deepening surface low, strong shear and good instability, I think there could be a real threat of strong/potentially long tracked tornadoes given the ripping mid level winds. Whether this threat covers the entire OV/mid south or just a localized corridor or two, I have no idea. And I'm normally a bit reserved for severe events. But without being able to know what the mesoscale is going to look like, there is a lot going for this event from a large scale perspective. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted February 29, 2012 Share Posted February 29, 2012 Please keep the back/forth snide remarks out of here, and try and keep the disco relevant to the weather and the setup. If you have personal remarks to make to each other, send it to PM. Link to comment Share on other sites More sharing options...
PatrickSumner Posted February 29, 2012 Share Posted February 29, 2012 I am hearing that the 18Z NAM isn't as impressive as the 12Z run... Link to comment Share on other sites More sharing options...
Cheeznado Posted February 29, 2012 Share Posted February 29, 2012 I am hearing that the 18Z NAM isn't as impressive as the 12Z run... It did back off some, not surprising since it was a big outlier. Still has very good severe parameters though.... Link to comment Share on other sites More sharing options...
Hoosier Posted February 29, 2012 Share Posted February 29, 2012 Per afternoon afd's, offices around here are leery about completely buying the NAM but not discounting a stronger/western solution. Link to comment Share on other sites More sharing options...
thewxmann Posted February 29, 2012 Share Posted February 29, 2012 All mesoscale, VVs, etc. aside, I still believe the main question regarding this system is the evolution of the upper-air features - the same problem that has been there from the beginning. If the GFS/CMC camp is right and the longwave trough gets stretched NE/SW, I don't really see much a sigtor threat north of the TN Valley as the main sfc low runs out ahead of the warm sector and low-lvl flow veers. The 12Z NAM, on the other hand, screams major outbreak. Link to comment Share on other sites More sharing options...
tornadotony Posted February 29, 2012 Share Posted February 29, 2012 All mesoscale, VVs, etc. aside, I still believe the main question regarding this system is the evolution of the upper-air features - the same problem that has been there from the beginning. If the GFS/CMC camp is right and the longwave trough gets stretched NE/SW, I don't really see much a sigtor threat north of the TN Valley as the main sfc low runs out ahead of the warm sector and low-lvl flow veers. The 12Z NAM, on the other hand, screams major outbreak. Yes. This. I know in past years, the GFS has often had a problem in the mid-range of stringing out UA energy for systems, thus causing them to end up farther NW/stronger than progged a couple days out. We shall see. Link to comment Share on other sites More sharing options...
andyhb Posted March 1, 2012 Share Posted March 1, 2012 Yes. This. I know in past years, the GFS has often had a problem in the mid-range of stringing out UA energy for systems, thus causing them to end up farther NW/stronger than progged a couple days out. We shall see. 18z run has the same problem. Link to comment Share on other sites More sharing options...
beneficii Posted March 1, 2012 Author Share Posted March 1, 2012 Yes. This. I know in past years, the GFS has often had a problem in the mid-range of stringing out UA energy for systems, thus causing them to end up farther NW/stronger than progged a couple days out. We shall see. Do you mean that the GFS's problem is that it models it too far east and south, when in reality it ends up to the north and west of where the GFS says it's going to occur? Link to comment Share on other sites More sharing options...
andyhb Posted March 1, 2012 Share Posted March 1, 2012 SREF members valid 57 hrs WRT the secondary SLP development: Link to comment Share on other sites More sharing options...
thewxmann Posted March 1, 2012 Share Posted March 1, 2012 Also, if you trace the origins of the wave that passes thru the OH Valley on Fri, it's coming onshore now, and the NAM is in its "believable" <= 48h range. Tonight's 0Z runs might be able to hone in closer on an exact solution. Link to comment Share on other sites More sharing options...
andyhb Posted March 1, 2012 Share Posted March 1, 2012 SREF members valid 57 hrs WRT the secondary SLP development: Should such a feature form, tornado potential would likely dangerously increase across TN southward across Dixie Alley as the LLJ strengthens and surface winds back in response to a deepening (and possibly rapidly deepening) synoptic sfc cyclone, this was a feature that Fred has been concerned with over the past several runs/days as the setup nears, and more and more models are now suggesting it. Link to comment Share on other sites More sharing options...
tornadotony Posted March 1, 2012 Share Posted March 1, 2012 Do you mean that the GFS's problem is that it models it too far east and south, when in reality it ends up to the north and west of where the GFS says it's going to occur? That has been a tendency of the past several years. That doesn't mean that's the case now, but it's something to keep in mind. Link to comment Share on other sites More sharing options...
beneficii Posted March 1, 2012 Author Share Posted March 1, 2012 That has been a tendency of the past several years. That doesn't mean that's the case now, but it's something to keep in mind. I know we had an issue with that in the past, but didn't they update the GFS's algorithm a few years ago to stop that problem? Link to comment Share on other sites More sharing options...
AtticaFanatica Posted March 1, 2012 Share Posted March 1, 2012 On a related note, SPC continues its tendency to be WAY too conservative in their 4-8 day outlooks, They almost never outlook an area if there is any sort of model difference, which is, well, practically always. I this case, there will be severe Friday, excact position not totally known, but come on, take a stand once in a while. They've done a lot of verification studies on various products (High risks, tornado watches, probabilistic forecasts, etc.), but I don't think they've done any verification work on the 4-8 day outlooks. I think that type of info (e.g, reliability diagrams) would be useful in objectively judging those outlooks. Link to comment Share on other sites More sharing options...
Hoosier Posted March 1, 2012 Share Posted March 1, 2012 NAM looks similar to 18z so far. Maybe just a touch quicker/farther east. Link to comment Share on other sites More sharing options...
Calderon Posted March 1, 2012 Share Posted March 1, 2012 Uh oh... Link to comment Share on other sites More sharing options...
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