02/05/08 FCST: TX,FL,GA,AL,MS,LA,TN,NC,SC,KY,VA,WV

[Justin E. Reed]

A large ridge will start to develop over the SE this weekend, allowing much warmer temperatures to penetrate all the way up into KY,WV and VA by Tuesday, bringing a healthy Southerly flow, loaded with warm temps and moisture from the GOMEX. A strong low pressure and trough will dig into the Plains by Monday, and move fast NEWD throughout MON-WED. An unstable airmass is very likely to be in place come Tuesday, and wind shear appears to be sufficient enough to allow for supercells, followed by a trailing squall lin along the frontl boundry. Unlike the previous event, temperatures will be warm across a large region, with plenty of moisture far north. Watching the models for the next few days, and by Sunday, we should have a general idea of the potential setup for Tuesday.NWS offices in Jackson, MS, and Mobile, AL have already stated the strong threat of severe wx on Tuesday.

NWS Jackson, MS:
A GREATER RISK FOR SEVERE THUNDERSTORMS EXISTS FOR LATE
MONDAY NIGHT THROUGH TUESDAY WHEN A STRONG COLD FRONT IS FORECAST TO
SWEEP ACROSS THE AREA. THE MODELS CONTINUE TO TREND MORE IMPRESSIVE
WITH THIS SYSTEM AND AT THIS TIME THEY SHOW NO LACK OF SHEAR OR
INSTABILITY. IF THIS CONTINUES THEN A SIGNIFICANT SEVERE WEATHER
EVENT COULD AFFECT THE ARKLAMISS REGION.

PERSONS IN THE OUTLOOK AREA SHOULD MONITOR LATER FORECASTS AND
OUTLOOKS CONCERNING THE SEVERE WEATHER POTENTIAL FOR EARLY NEXT WEEK.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS...MAY BE NEEDED FOR A TIME LATE ON SUNDAY BUT MORE
LIKELY OVER THE ENTIRE AREA ON TUESDAY.

 

[Justin Bailey]

I agree, its definately looking really interesting for much of the mid ms vly, ohio vly, tn vly, and deep south. however it is still a ways out. but you can bet your butt i'll be keeping an eye on the models til it gets here! these type of systems real early in the year tend to catch a bunch of people off guard!

 

[Brett Adair]

Very interesting indeed. BMX is honeing in on this event as well. Current inidications show very impressive wind fields overtop of some descent instability for a change. My biggest question would be does the mid level trough hang back. The GFS has shown a split of the energy with a wave riding north across the midwest and into the Lakes region instead of phasing things up. It still looks like a severe weather setup for a big area, but a potential outbreak situation if the phasing solution occurs overtop the Theta-E ridge/Instability axis.

 

[Justin E. Reed]

A few classified military models I ran this morning have painted a very very bad situation. Incredbile levels of shear, I have not seen shear like this on this model, so I researched, and boom, popped out a close run to April 7,2006. Temps are going to be in the 70's all the way up to Nashville, and mid 60's to Louisville, with dewpoints 55-60 that far north, and 60-65 in in Alabama, Mississippi and Louisiana. More than ample instability, the one kicker though, low clouds, as is usual this time of year with systems like these. Although, enough warming of the clouds could cause them to break up and allow enough sun to really get things going. I expect supercells, some strong ones at that in MS, LA, AL, and possibly TN, with a likely damaging squall line up to OH, IN, and KY, and then trailing with the front further south.

 

[Brett Adair]

The WRF is also showing sufficient instability now especially across CNTRL/ERN MS and WRN AL for explosive development Tuesday afternoon. Good shear combined with upper level support looks to make for an active afternoon. Low level CAPE is pretty high, so some significant tornado development will be possible with sustained supercells well ahead of the cold frontal boundary itself. Nice SFC convergence also looks to allow for supercells to develop over this region as the SFC cyclone intensifies and moves NE with high pressure on the east coast. Still a few days to go, but this continues to look like a potential higher end event.

 

[George Tincher]

There doesn't seem to be much point trying to pin down all the specifics this far in advance. But the GFS is progging a 1001mb low which will be centered over ERN OK at 12z Tuesday to move NE and deepens it to 992mb, reaching C IN by 00z with a fairly strong cold front extending off to the SW. The latest NAM run shows a relatively similar solution.

Both models seem to indicate dewpoints into the mid 50s will be pulled as far N as NW OH during this period in advance of the front, with mid 60s dewpoints reaching as far N as WRN TN with even stronger values along the Gulf Coast. Strong, deep layer shear appears to be likely over the entire region. So the stage appears to be getting set for another severe weather event Tuesday.

Now, as to type of severe weather, it appears (at this point anyway) that this will likely be a wind damage event primarily, as models want to quickly congeal this activity into a line. However, 0-6km shear seems sufficient for supercells over much of this area. There's not as much low level turning as I like showing up yet, but there is decent directional shear (southerly at the sfc, gradually turning to the SW with height) and very strong speed shear. I could certainly see tornadoes within the line to be a distinct possibility. And should any discrete action be able to form in advance of the line, there appears to be more than enough helicity to get them spinning. However, it seems CAPE appears to be showing up a little weaker than I would expect given the other projected parameters and conditions. Perhaps the model is having issues dealing with precip or something? The 0-3km CAPE looks a little better. Ah well, it should be better resolved going foward.

BTW, the SPC has now placed a huge 30% severe probability area in the SLGT risk on the new Day 3 outlook, extending from N of the Ohio River in IL, IN and OH all the ay to the Gulf Coast. This thing may very well get upgraded to a moderate risk by the time we hit Day 2. Looks like Tuesday will be a long day for folks in the OH and TN Valleys, all the way down to the Gulf.

Good luck to anyone who chases this. Storm motions look pretty speedy, especially over the NRN portion of the threat area.

 

[nickgrillo]

WRF sure paints a favorable synoptic environment for supercells (and tornadoes) on Tuesday afternoon, particularly from southern IN into western KY and TN. Strong deep-layer flow will poise for favorable kinematic profiles for strong and sustained surface-based supercells with the possibility of a strong tornado or two given the forecasted boundary layer SRH (with good low-level hodograph curvature closer to the sfc low, given the veering boundary layer flow) and moisture depth.

 

[Justin E. Reed]

I'm really starting to smell a MDT risk being thrown out tomorrow for Northern MS, NW AL, W & MDL TN, W KY, and possibly up to S IN. Atleast from what all the models are throwing out there. It's going to be quite breezy in Middle TN, 20-30 gusting to 40 at the surface, which is quite brisk for this time of year.

 

[Heidi Farrar]

I think we could add AR, MO, IL, IN & OH to the subject line

As of the most recent model runs, the WRF & GFS have come down slightly on CAPE projections for AR/MO over this period, but we're still looking at values from 500-1000+. ... I, too, was struck by the SPC's wording in regard to the wind fields:

THIS SYSTEM WILL BE ACCOMPANIED BY VERY STRONG DEEP-LAYER WINDS...INCLUDING A SSWLY H8 JET IN EXCESS OF 70 KT AND H5 FLOW WELL IN EXCESS OF 100 KT IN THE JET CORE AND AS HIGH AS 90 KT ATOP THE WARM SECTOR.

To me, this set-up is pretty reminiscent of the SW MO event in January, but with higher levels of instability likely to be in place over a much wider area. I expect to see a mod. risk for Tuesday over central AR east into the lower OH valley & middle TN & northern MS.

 

[Terry Tyler]

man, this is starting to look better and better as the time wears on...im starting to get excited...

latest NAM run shows a 120KT jet core...60+ tds and 140-200 0-3KM cape, and 0-1KM SRH of 200-300...instability and wind profiles are looking very stout...just experiencing 1-10-08 and now this?!

the sfc low is going to be sitting right where i always want it for these kind of set-ups central KS/MO...

 

[Brett Adair]

I'm thinking with the orientation of the SFC low, you can add most of AL/MS and maybe NW GA to that MDT risk. Pretty good shot at seeing a high risk if the instability ends up being stronger than currently forecast. The EML will have alot to do with that. Looks like the NAM/WRF wants to paint supercells over much of MS/TN/W AL well ahead of the FROPA. 0-1km Shear values definitely concur with that idea from this mornings run. I believe that we are looking at a fairly high end event from the OH valley all the way to the Gulf coast.

 

[Justin E. Reed]

Very concerned

Many offices are calling for a SIGNIFICANT severe wx event for Tuesday. high temps will be in the 70's in Middle TN, IN FEBRUARY!, also, near 70 in Louisville, KY, that is a very bad sign and rare for this time of year. Instability will not be an issue, just the amount of sunshine will be the bigger issue, but with Lapse rates, shear, CAPE, and others this significant, it really won't matter. These stroms will explosively develop, and quickly tap into the shear, and begin to rotate. I'm am gettin concerned about this situation, its somewhat reminicent of the setup for the April 7,2006 outbreak!, and we all saw what happened then. I was even able to dig up data that some of these models are producing, and April 16,1998 popped up. That produced the unforgettable Downtown Nashville F-3, the Waynesboro F-5, and hail the size of softballs and a 99mph gust at Nashville Int'l Airport(KBNA). This situation, to me, has HIGH written all over it, along with a large MDT risk.

 

[Brett Adair]

Many offices are calling for a SIGNIFICANT severe wx event for Tuesday. high temps will be in the 70's in Middle TN, IN FEBRUARY!, also, near 70 in Louisville, KY, that is a very bad sign and rare for this time of year. Instability will not be an issue, just the amount of sunshine will be the bigger issue, but with Lapse rates, shear, CAPE, and others this significant, it really won't matter. These stroms will explosively develop, and quickly tap into the shear, and begin to rotate. I'm am gettin concerned about this situation, its somewhat reminicent of the setup for the April 7,2006 outbreak!, and we all saw what happened then. I was even able to dig up data that some of these models are producing, and April 16,1998 popped up. That produced the unforgettable Downtown Nashville F-3, the Waynesboro F-5, and hail the size of softballs and a 99mph gust at Nashville Int'l Airport(KBNA). This situation, to me, has HIGH written all over it, along with a large MDT risk.

Generally thinking the same thing here. The combination of shear/dynamics/instability is by far the best we have seen in a while with no coastal convection to block off warm inflow.

 

[Jeff Snyder]

I haven't looked at the forecasts TOO much, but I can't be as gung-ho about the threat as others seem to be. From a kinematic standpoint -- yes, things look very interesting for a significant severe weather event. However, kinematics are not everything, as we all know. I just can't help but have a tempered forecast owing to the forecast marginal instability, or downright lack of instability as one moves into the Ohio River valley (or much north of Paducah, KY). Right now, I think the lack of significant destabilization may prohibit a significant tornado event (particularly one that would deserve a HIGH risk) across most of the area. Yes, high-shear environments have support significant tornadoes and widespread supercells in spite of marginal instability, but I have a hard time putting together a forecast for a significant tornado event or outbreak when we see instability as weak as it is forecast to be (largely, <750 j/kg in most of the areas being highlighted in this thread). My interest is higher farther south (say, southeastern AR, west-central and southwestern MS, and much of La) where it appears destabilization may result CAPEs closer to 1000 j/kg.

As it is now, it's looking to me like a relatively widespread wind event (with significant wind events) similar to what we saw last week in the KY/IL/IN/OH. I do expect to see a threat for strong tornadoes south of the Paducah area (namely, western TN, eastern AR, LA, and MS), but I'm not sure that tornadoes will be the primary threat. Model forecast CAPE fields likely are going to be sketchy given the widespread convection being developed by the models (with the resultant widespread decrease in CAPE owing to convective parameterization). Regardless, though, I have to wonder if we'll see "strung-out" supercells that get ripped to shreds in a relatively low CAPE, high shear environment. Obviously, vert. perturb. pressure gradients may well contribute more to updraft intensity than buoyancy / CAPE given the strong shear, but I'm not convinced that it may be enough.

 

[George Tincher]

The amount of SBCAPE forecast by the models thus far does look pretty puny anywhere outside the Gulf Coast, particularly LA and MS. However, taking a look at 0-3km CAPE paints a much different picture:

Considering the time of year, I am not overly surprised that SBCAPE is not highly impressive. However, that low level CAPE looks very impressive and over a wide area. Considering everything else, I think that is very significant. And FWIW, I see better instability with this system than some that have occurred already this year that produced tornadoes. I mean we saw a long track F3 in Wisconsin in CAPE values that barely hit 500j/kg. Sometimes you just never know.