03/01/07 FCST: AR / MO / KY / TN / AL / IL / MS

Time to think about this one. It's a ways off, but it's starting to look like an exciting possibility. A compromise between NAM and GFS suggests a surface low between northern MO...to western IL, with a trailing cold front trailing SWWD into OK/Central TX. I knows it's a little early, but any input??
 
If the 12z ETA is close to verifying, the main supercell threat should occur Thur. afternoon across far E. Arkansas, W. Tennessee, MO Bootheel, into N. Mississippi and Alabama. The instability and shear forecasts show enough there for tornadic supercells. Need a few more runs to see get an exact target nailed down. Timing will be critical with this system. If the pre frontal trough hits during the mid-late afternoon hours, things could get very interesting.
 
This one caught my eye as well last night, and luckily enough it's still there on this mornings run. Does indeed paint a strong surface low moving from Missouri into Indiana during the day. Best area right now looks like it might be the southern half of Illinois into Kentucky and maybe SW Indiana where the surface front will be located during peak heating, and surface winds should be backed slightly. Unlike this past system, we should be rid of most of the snow cover so temperatures in the 60s don't seem out of the question. Moisture seems decent at this point as well, td's in the mid 50s forecast over the area. There really isn't a lot you can say at this point... we can just hope it's there again on tonight's model run!
 
Well things definitely starting to go in favor of a severe weather event.. Models have went back to the northwest track.. Which could even mean severe weather here in Illinois. Given this time of year.. Insolation will be critical. If any area can see sunshine.. It would definitely enhance the threat.. Ill post more in depth analysis after im out of class and get home
 
The NAM and GFS are pretty close on this setup. Have the models been improved this season? I was amazed how well the GFS and NAM performed on the last setup.

Anyway, this is going to send a screaming squall line from IL down to the southern states by the looks of this run. What we can hope for though is initiation along the warm front during the afternoon hours before the cold front sweeps through. Surface winds will be nicely backed and excellent veering with height, but the cap might be more of an issue.

Instability is plotted in Alabama, a mere 500 JKg, but with excessive SRH values over 300. The southern folks should definitely keep an eye on this one too.

Another active early season?
 
Dews per Cod nexlab put 60+ dews through all of SEMO, several counties in SO. Il. All of W. Ky. Temps easily in 60's, Sometime after 1800 hrs. things could get very interesting....... Question is with helicities outrunning setup a bit. Overall is a very favorable environment for quite an event if this keeps up....
kevin
 
Question is with helicities outrunning setup a bit.

SRH values will be lacking along the cold front if that's what you mean? I think if we can get anything chaseable out of this system, it will have to initiate well ahead of the linear line in the warm sector.
 
WRF painting an ominous picture for the midwest/south. GFS does the same, but based on the track, should not post such a threat over central IL. But based on the GFS south bias this winter season, I will side with the WRF RUC and ECMWF. Which take the low to A.O.A 80 miles east of Des Moines IA at it's strongest point.. This should be another <990 mb storm. Think the lowest it hits is 982. Which would put it as a stronger system than this past week. :eek: Two waves to deal with with this system.. But will stay in the time range of the thread and only deal with the Thursday event. Low pressure will move NE out of Kansas and up through NW Missouri and into Central IA. Bringing along with it the associated precip and frontal boundaries. CAPE seems to be pretty impressive for late winter. With 600-800 common across the entire area. Moisture transport seems to be doing well. With forecast dew points of 53 degrees at my location in western IL. SCP's seem to be favorable close to the low/triple point in central il. LI's are pretty impressive from central IL southward. My thoughts are.. For here in western il.. if we dont see severe weather here, a short drive south/southeast ought to do great! Hope the models keep this one coming!!
 
This one has all the capabilities of out-doing the one over last weekend. Dew points better, instability, etc. Models suggest relatively warm and moist boundary layer will spread further NWD than the previous system. looks like the highest threat will be the western 80% of Tennessee. It's early I know, but IMO...Paducah to south of Nashville. Shear will be awesome, and there is NO arctic air to displace either. I'm trying to find a real negative posibility here, and I can't. This one looks widespread, but I'm making my plans now.
 
Well.....this event looks much better for the Alabama folks this go round than this past event. We have pretty impressive shear and instability forecast. The WRF/GFS have went up and down with instability values, but SFC temps and dewpoints have remained consistently in the low-mid 70's (temps) and mid-upper 60's (dewpoints) across Central AL. We have had our most violent outbreaks with SSW winds at the SFC and being in the right entrance region of the upper level jet (supposed to be the subsidence side). For example....4/3/74....5/18/95....11/10/02....4/8/98. 4 outbreaks listed there in which large and violent tornadoes caused death and destruction across the south. Lapse rates during those were between 6-7 as well. Looks to be pretty similar with alot of the features this time. Being in the right entrance of the ULJ, our activity could be more discrete due to a little less lift in this area before taking a powerful squall line along this front. I do believe we could have some rather large torndoes here in the deep south.
 
Well this mornings model suite make me ponder again.. I noted that the UKMET bombs the low out at an amazing 978 mb!!!!:eek: :eek: :eek: This may be a little unbelievable though. Furthest southeast of the models would be the GFS. Which takes the low just west of the MS river valley.. Up here in IL initial threat is going to be nocturnal convection. Possibly severe. Dont know how the storms will hold together this time of year.. Moisture still looks to be fine.. I agree with the SPC outlook.. I think they could be further N or NW.. But the highest risk in the day 3 looks appropriate. When this system comes on shore, hopefully these finite details can be resolved.
 
Looks like the occlusion triple pt. should be near Memphis TN Thur. afternoon...looks like a pretty solid case for a MDT risk across southern sections of West & Middle Tennessee, N. Mississippi, N/C Alabama, and maybe even extreme E.Arkansas the way things look. Excellent deep layer shear, strong 0-1km shear (30-45kts.), and decent 0-3km CAPE is forecasted for Thur. afternoon. This should make for a pretty active severe wx/tornado day across the Mid-South/Tennessee Valley. I would not be surprised to see more in the way of tornado reports than with this past Saturday's (2/24) storm. The SPC Day 3 forecast looks very well placed for this event.
 
Well....looking at things, I do believe that I am getting very close to setting up in Tuscaloosa, AL on Thursday by noon at the latest. Things could kick off if we meet the convective temp. Just have to hope that warm front doesn't screw things up with isentrophic precip before the CAPE gets here.
 
I don't think I've ever said this before....but....I'm thinking it may actually go "HIGH" risk before it's over. I'll be on the AL/MS border, just south of the TN state line. Was in this exact same place last year, when a tube hit Cherokee, MS. Dewpoints could reach close to 70 (SEVENTY) in these areas, and even close to 65 in the Carolinas by Thursday night. Instability will be marginal, but with so much going on towards a very active day, I don't see that as a problem..at all. So for now....Florence, AL is my target.
 
I also really like this setup, and hope for all concerned that some good chasing comes out of it all. Still, there are just a couple of things that concern me. In the latest GFS I'm not that impressed with the strength of the cap. If initiation along the frontal boundary happens too soon, those awesome shear values are going to rip the tops right off the best sup's.

Then the whole thing might congeal into a giant linear mess. Any thoughts or input on this?

John
www.skywatch7.com
 
Well this mornings model suite make me ponder again.. I noted that the UKMET bombs the low out at an amazing 978 mb!!!!:eek: :eek: :eek: This may be a little unbelievable though. Furthest southeast of the models would be the GFS. Which takes the low just west of the MS river valley.. Up here in IL initial threat is going to be nocturnal convection. Possibly severe. Dont know how the storms will hold together this time of year.. Moisture still looks to be fine.. I agree with the SPC outlook.. I think they could be further N or NW.. But the highest risk in the day 3 looks appropriate. When this system comes on shore, hopefully these finite details can be resolved.

Yes, and the 12z NAM and GFS deepens it to 977 and 981 mb respectively over eastern Iowa/ SW Wisconsin.
 
This system is continuing to show prolific shear profiles with a military only model run:eek: . I have gone back into archives and the following events are similar to this set up. April 8 and 16,1998 and April 7,2006. This is a situation that is likely to get going, and very explosively, one model I ran just now, took a normal thunderstorm to supercell with strong rotation in just 2 hours! WTF! I am stressing this is a dangerous situation, I am expecting a rather sizeable outbreak, powerful supercells with incredible gate to gate shear and a possible prolific squall line, if not supercells for Atlanta, all the way the Tallahassee. We'll see how this pans out, by I am predicting a dire weather situation to kick off March. This one is not a lion, this is an elephant on crystal meth, I'm keeping my relatives abreast to this likely dangerous situation.
 
After letting the model run for another hour, the storm that I made(mentioned above), at the 3 hour mark, has radar velocities maxed out, a total gate to gate max out. This is rather odd and I'm sittin here stunned and confused, but hey, its the computer running it. Highly worried about NE MS, N AL and Mid TN, this is a very volatile setup.
 
After letting the model run for another hour, the storm that I made(mentioned above), at the 3 hour mark, has radar velocities maxed out, a total gate to gate max out. This is rather odd and I'm sittin here stunned and confused, but hey, its the computer running it. Highly worried about NE MS, N AL and Mid TN, this is a very volatile setup.

I'm curious. What model are you using, and are you initializing it with an inhomogeneous analysis, like the operational forecast models, and running at high resolution over a limited domain, or are you taking forecast soundings and initializing small, idealized domains with a thermal bubble to see what kind of storm structure you get?
 
I wish I could say, but it is SECRET material under Dept. of the Navy. It utilizes every single bit of information that you can gather, soundings are one of the better parts of it. I just can't say too much, but the fact that my Commanding Officer was freaked by this output of the model, raises a big red flag, stations in Nashville are already starting to get a little gloom and doom over this, for all the right reasons.
 
I really hate comparing systems and I hate even more to hype systems. But I can't help seeing a big event shaping up when I look at Thursday. And it is somewhat comparable to other systems that have really caused lots of problems for areas of the south such as TN, MS, and AL. The person who said it's possible that this may end up being a high risk before all is said and done may end up being correct. It's certainly a very solid moderate. I see a much more favorable severe weather setup for this one than with the last system. Moisture looks much better for one thing and it appears decent moisture levels and increased sfc tempertures will make it much farther N than last time, which could make this one a bit more widespread. This setup appears to have much more in common with what you might expect to see in April, rather than what you would expect to see in February (the previous system).

So far I think the SPC has done a good job highlighting the areas most at risk, but I would not be too surprised to see areas farther N into KY, SRN IL and SRN IN get in on the action as well, if good moisture proves to not be an issue.

That said, right now it appears that cities such as Memphis, TN....Nashville, TN....Columbus, MS....Huntsville, AL....Birmingham, AL....etc, may be in for a very long and a very rough day come Thursday. Now I'll need to go look at the latest model data as it comes in to see if everything I have just typed has gone out the window or not. Hehe.
 
I wish I could say, but it is SECRET material under Dept. of the Navy. It utilizes every single bit of information that you can gather, soundings are one of the better parts of it. I just can't say too much, but the fact that my Commanding Officer was freaked by this output of the model, raises a big red flag, stations in Nashville are already starting to get a little gloom and doom over this, for all the right reasons.

See the new thread I've opened up on the "Weather and Chasing Board" about this topic, since my reply is somewhat off-topic.

http://www.stormtrack.org/forum/showthread.php?p=124169#post124169
 
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one model I ran just now, took a normal thunderstorm to supercell with strong rotation in just 2 hours!

This actually seems unimpressive to me in the sense that many times we see thunderstorms develop and become tornadic with great shear values in 1/2 or so. 2 Hours seems like a long time for a TRW to go tornadic with those shear values in an explosive environment.

Nevertheless, it looks like potent setup and one that should be fun to watch. As far as the Navy model goes, it's hard to comment on it or it's performance when you don't know anything about it.
 
Well, I'm prepping the system to run at 2300L, it is showing a change,. ironically you metinoed half the time, the whole model system is collecting the newest data and is processing for a run. The run should be done by 2330 or just after 0000L. I will definetly post my new findings as soon as they come flying out of the printer.
 
I'd imagine the Day 2's slight will extend well into central Illinois. Earl Barker's NAM CAPE plots have 500 JKg extending up to about Springfield. At 18z Carbondale looks pretty good. 750 JKg isn't much, but with the 979 low in IA, 60 knots 6km shear, 40 knots 1km shear and 300 3km SRH, the meager instability will be more than made up for by the dynamics. I'm looking at 18z because the cap looks pretty weak and there may be quite a bit of forcing with the jet as strong as it is. Early show in southern IL?
 
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