Severe Weather again possible for South into Ohio Valley...

[yoda]

http://www.spc.noaa.gov/products/outloo ... l#topimage

Does anyone else see this? KOW, Purdue? I find this interesting because it states that there may be a sig svr wx otbrk... and that is uncommon in December.

[snowflake]

I hope it does not get to bad and moves out quickly.

[vbhoutex]

At best it is saying that a few strong cells may happen. I see the statement you are talking about Yoda, but they are downplaying the probability if they are doing anything. Yes the possibility for a destabilization leading to some severe weather exists, but is not extremely likely is how I read it, especially at this time of year and in the areas mentioned. If anything does happen it will be in the deep south it appears.

[dvdweatherwizard]

First of all, this is my first post ever here! Yay! Also, I REALLY like the games forum here as well. Okay, moving on now........

I think there will definitely be some severe weather from eastern TX, AR, LA, MS, southern TN, and AL starting on Monday in eastern TX and pushing eastward from there into Tuesday. Here are some maps that would likely support some severe weather in those areas.....

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _054.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _060.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _066.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _072.shtml
http://www.nco.ncep.noaa.gov/pmb/nwprod ... _078.shtml

http://weather.cod.edu/forecast/UKMET/u ... spd_60.gif
http://weather.cod.edu/forecast/UKMET/u ... spd_72.gif
http://weather.cod.edu/forecast/UKMET/u ... ort_60.gif
http://weather.cod.edu/forecast/UKMET/u ... ort_72.gif
http://weather.cod.edu/forecast/UKMET/u ... emp_60.gif
http://weather.cod.edu/forecast/UKMET/u ... emp_72.gif
http://weather.cod.edu/forecast/UKMET/u ... rec_60.gif
http://weather.cod.edu/forecast/UKMET/u ... rec_72.gif

From these maps, I see the areas that I outlined in general being on the right rear side of the jet streak that occasionally reaches 130 knots, in front of a potent little 500 mb shortwave, in the vicinity of a strengthening low-level jet with time at 850 mb that eventually strengthens to over 50 knots, which also drags +12C air at 850 mb into southern TN eventually, and the area is in general on the proper side of the deepening surface low. There also might be a little bit of turning of the winds with height in the beginning over eastern TX too.

Now, I would think the limiting factors to this would be the fact that we're still three days away from the event, and it's hard to really pin down a threat of severe weather that far away in time because the details could easily change. Also, one important map that I didn't post a link too would be a forecast of CAPE from somewhere for these time periods. I don't have access to one that I can quickly post, so I would be interested to see what the models are showing with respect to instability for this time. If I had to guess, I'd have a feeling they weren't showing that much right now because it always seems, at least to me, that they underestimate the instability some in the extended forecasts.

Oh well, that's what I see right now for what it's worth. I personally don't think this will be as bad as the last outbreak back in November, but I do personally believe right now that the SPC will go ahead and upgrade to a moderate risk for central and northern LA, and central MS at some future outlook. Instability will definitely be the limiting factor I think in that case though. It is December after all like Yoda pointed out. We'll just have to wait and see!

**EDIT: Added the links to the 850 mb maps and surface maps for the UKMET model, which I somehow forgot before. Also, if you view this post later, I should add that at the time I posted this, the model runs shown were the 12Z GFS from Saturday, December 4th, and the 00Z UKMET from Saturday, December 4th.

[SouthernWx]

It looks potent....and unusually potent for early December.

Saying that, intense tornadoes occur more in December than some might think...especially from Georgia west to Louisiana and northward into the lower Ohio Valley. A F5 tornado in December 1953 killed 38 in Vicksburg, Mississippi. A series of violent tornadoes, including one F5 took many lives in southern Illinois in December 1957. As recently as 2000, a large violent (F4) tornado roared across the southern portion of Tuscaloosa, Alabama...killing 11.

Although significant tornadoes don't occur during December every year, when the atmospheric conditions are right....they can and do occur (even on Christmas Eve and Christmas Day, as occurred here in Georgia in 1964

At the present time, the highest potential for significant tornadoes and/ or extensive wind damage appears to be across Alabama, Mississippi, and Tennessee on Monday. This is a potentially very dangerous storm system that should be monitored by everyone in the southeast and mid-south....as well those in the Tennessee and lower Ohio Valleys.

If current model trends verify, there will also be the potential for another severe weather outbreak across the southern U.S. late next week (Fri-Sat/ Dec. 10-11).

PW

[dvdweatherwizard]

Forecasters at the Jackson, MS and Birmingham, AL offices are definitely concerned about this system as well. Here are some snippets from their afternoon AFDS from Saturday......

from Jackson.....

THE MAIN SHOW IS EXPECTED TO COME MONDAY NIGHT AND EARLY TUESDAY AS
A STRONGER DISTURBANCE IN THE WAKE OF THE FIRST DRIVES A COLD FRONT
INTO THE STEAMY AIRMASS IN PLACE. THIS SYSTEM IS BEGINNING TO SHOW
MORE SIMILARITIES TO THE ONE THAT PRODUCED ALL THE SEVERE WEATHER A
WEEK AND A HALF EARLIER. ONE ASPECT WHICH IS FALLING IN LINE WITH
THE FIRST IS THE TIMING AS MODELS ARE NOW AGREEING MOST OF THE
CONVECTION SHOULD OCCUR MONDAY NIGHT. LEVELS OF WIND SHEAR
FORECASTED WITH THE CURRENT SYSTEM ARE IMPRESSIVE AND THE NEARBY
RIGHT ENTRANCE OF A 100+ KT UPPER JET WILL HELP PROVIDE SUBSTANTIAL
LIFT. THE ONE ATMOSPHERIC FEATURE THE PREVIOUS SYSTEM HAD MORE OF
WAS ATMOSPHERIC INSTABILITY. THIS MAY BE THE LIMITING FACTOR THAT
KEEPS ANOTHER OUTBREAK OF SEVERE STORMS AND TORNADOES FROM
OCCURRING. HOWEVER...THIS IS NOT TO SAY THAT SUCH AN OUTBREAK IS NOT
AGAIN POSSIBLE...BUT FORECASTER CONFIDENCE IS NOT AS HIGH AS IT WAS
THIS LAST EVENT. ONE THING TO NOTE IS THAT EVEN IF REALIZED
INSTABILITY IS MARGINAL...AS THE MODELS ARE PREDICTING...WE STILL
SHOULD SEE A NASTY SQUALL LINE WITH DAMAGING WINDS AND THE THREAT
FOR AT LEAST ISOLATED AND WEAK TORNADOES.


and from Birmingham......

MODELS ARE TRENDING TOWARD A SLOWER FROPA...WITH FRONT NOT REACHING
WEST ALABAMA UNTIL 12Z TUESDAY. WITH MUCH OF THE AREA HAVING BEEN
IN THE WARM SECTOR FOR ALMOST A FULL DAY...AND SUFFICIENT SHEAR
DEVELOPING AS UPPER LEVEL SYSTEM APPROACHES...CONDITIONS ARE
TRENDING TOWARD ANOTHER SVR WX EVENT FOR LATE MONDAY INTO TUESDAY
MORNING. SHOULD HAVE A MUCH BETTER HANDLE ON SITUATION BY TOMORROW.

taken from http://iwin.nws.noaa.gov/iwin/ms/discussion.html and http://iwin.nws.noaa.gov/iwin/al/discussion.html

[dvdweatherwizard]

THE ONE ATMOSPHERIC FEATURE THE PREVIOUS SYSTEM HAD MORE OF
WAS ATMOSPHERIC INSTABILITY. THIS MAY BE THE LIMITING FACTOR THAT
KEEPS ANOTHER OUTBREAK OF SEVERE STORMS AND TORNADOES FROM
OCCURRING. HOWEVER...THIS IS NOT TO SAY THAT SUCH AN OUTBREAK IS NOT
AGAIN POSSIBLE...BUT FORECASTER CONFIDENCE IS NOT AS HIGH AS IT WAS
THIS LAST EVENT.

The one thing that concerns me somewhat about this is that I thought with the last outbreak that occured, didn't the models end up also underestimating the instability for that event compared to what ended up materializing? I could easily be wrong, but I think I remember that they did to some extent. It will be interesting to see what happens this time with respect to the instability forecasts vs what actually ends up materializing. I think the Jackson forecaster might have hinted at this when he or she said, "HOWEVER...THIS IS NOT TO SAY THAT SUCH AN OUTBREAK IS NOT
AGAIN POSSIBLE..." Time will tell I guess.

I think that was fantastic information provided by SouthernWx
about intense tornadoes and the month of December. It goes to show we can NEVER let our guard down when it comes to severe weather. Even though I personally think this event will fall a little short of the last outbreak, it still seems to look quite nasty.

[dvdweatherwizard]

Here's a couple of really cool websites to monitor the upcoming severe weather event with.......

http://www.spc.noaa.gov/compmap/
http://www.spc.noaa.gov/exper/mesoanalysis/

That last website especially has just about everything you could dream of on it..........but mainly I think they could be very useful for monitoring the hour by hour trends in the instability parameters since that factor would seem to be very important for this upcoming event.

[Skywatch_NC]

Last night the chief met Greg Fishel (WRAL-TV5) here in Raleigh during his forecast maps sequence...anyway he said that there could be a chance of a few thunderstorms here Tuesday...the high that day is forecast to be in the upper 60s.

I'm not aware of any tornadoes occurring in December here in NC...have lived in this state only since 1988...but in November of '88 an F4 touched down in some suburbs of Raleigh (I've only lived in Raleigh though since late March of this year).

http://www4.ncsu.edu/~nwsfo/storage/cases/19881128/

Eric

[dvdweatherwizard]

Last night the chief met Greg Fishel (WRAL-TV5) here in Raleigh during his forecast maps sequence...anyway he said that there could be a chance of a few thunderstorms here Tuesday...the high that day is forecast to be in the upper 60s.

I'm not aware of any tornadoes occurring in December here in NC...have lived in this state only since 1988...but in November of '88 an F4 touched down in some suburbs of Raleigh (I've only lived in Raleigh though since late March of this year).

http://www4.ncsu.edu/~nwsfo/storage/cases/19881128/

Eric

This seems to be an interesting site for tornado information. http://www.tornadoproject.com. It will even break down the tornado reports by county! According to this part of the site, http://www.tornadoproject.com/alltorns/nctorn.htm , there have been 7 tornadoes in NC in the month of December from 1950 to 1995.

DEC 03, 1967 0815 0 0 F2
DEC 25, 1974 0355 0 0 F1
DEC 01, 1967 1830 0 0 F2
DEC 26, 1964 0830 0 1 F1
DEC 31, 1975 1615 0 0 F0
DEC 31, 1975 1530 0 0 F1
DEC 31, 1975 1600 0 0 F1

The column after the date represents the time, the next column represents deaths, and the one after that represents injuries. Two of the Dec 31, 1975 tornado reports ocurred in adjacent counties (Durham and Wake), so I wonder if they were in fact the same tornado. Otherwise, it seems as though there hasn't been a tornado in NC in December in a very long time, and even then, there has never been anything worse than an F2 according to the info on that site, and there have been no deaths and only one injury in December!

[michaelwmoss]

This storm looks very simliar to the last one that went through here with Tornadoes in the South and then a view in the Ohio Valley SE Indiana, SW Ohio. They mention that "Dry Slot" Again which happened in the last storm and that is where the Tornadic storms in Indiana and Ohio Developed well after a large squall line blasted through the SE with Tornadic Supercells ahead of it.

Looking to be a very simliar scanario. I would look for some Isolated Moderate Risks to be issued

[breeze]

Monday night looks to be the good timing for
severe weather for us. It's not uncommon, at all,
for Tennessee, especially the southern counties,
to have tornado outbreaks in December & January.
Our coldest winter weather doesn't usually hit
until mid-February.

[michaelwmoss]

Maps still show Slight risk from Indiana on Southward. Be interesting to see the morning outlooks.

[SouthernWx]

Here's the new SWODY, and as I expected.....there is now a moderate risk of severe storms and possible tornadoes across much of the mid-south later today and tonight. In fact, I expect the moderate risk area to be extended eastward into northern/ western Alabama and farther southeast into Mississippi; and the slight risk area eastward to near the Alabama/ Georgia border.

This is potentially a very dangerous weather situation unfolding....and one or two intense tornadoes won't surprise me in the moderate risk area (especially Mississippi into western Tennessee and eastern/ southern Arkansas.

SPC SWODY1

[yoda]

Good post Perry. It appears SPC agrees with its 0600 outlook...

...CENTRAL TX NEWD INTO THE MID AND LOWER MS / LOWER OH VALLEYS...
MAIN BAND OF WARM ADVECTION AND ASSOCIATED PRECIPITATION CONTINUES
MOVING EWD INTO THE ERN CONUS ATTM. HOWEVER...CONVECTIVE THREAT
WILL INCREASE ACROSS THE S CENTRAL U.S. EARLY IN THE DAY 1 PERIOD AS
UPPER TROUGH APPROACHES. SURFACE LOW NOW OVER FAR SERN CO / SWRN KS
IS FORECAST TO DEEPEN / MOVE TOWARD S CENTRAL KANSAS THROUGH THE
DAY. ASSOCIATED COLD FRONT IS FORECAST TO MOVE EWD TOWARD CENTRAL
OK / CENTRAL TX...WHILE WARM FRONT AT THE LEADING EDGE OF MOIST GULF
AIRMASS /UPPER 60S TO LOW 70S DEWPOINTS/ RETREATS NWD ACROSS SERN OK
/ SRN AR / THE LOWER MS VALLEY.

THOUGH HEATING SHOULD BE LIMITED DUE TO CLOUDINESS / LIGHT
PRECIPITATION...UVV AND MID-LEVEL COOLING AHEAD OF MAIN TROUGH
SHOULD RESULT IN MARGINAL DESTABILIZATION -- PARTICULARLY S OF WARM
FRONT. ATTM...IT APPEARS THAT STORMS WILL LIKELY EVOLVE / INTENSIFY
ALONG RETREATING WARM FRONT AND PERHAPS WITHIN THE WARM SECTOR
ACROSS PARTS OF E TX / SERN OK / AR / LA...AS WELL AS ALONG
ADVANCING COLD FRONT ACROSS CENTRAL OK / CENTRAL TX.

VERY STRONG SWLY MID-LEVEL FLOW -- IN THE 65 TO 85 KT RANGE -- ABOVE
STRONG / VEERING LOW-LEVEL WIND FIELD IS FORECAST TO SHIFT EWD INTO
A LARGE PORTION OF THE S CENTRAL CONUS BY AFTERNOON. THIS SUGGESTS
THAT ANY STORMS WHICH DEVELOP ACROSS THE REGION WILL ENCOUNTER
SUFFICIENT SHEAR TO BECOME SEVERE / SUPERCELLULAR. ALONG WITH A
THREAT FOR DAMAGING WINDS...DEGREE OF LOW-LEVEL TURNING / SHEAR AND
MOIST LOWER TROPOSPHERE FAVOR LOW-LEVEL ROTATION AND THE POTENTIAL
FOR TORNADOES. GREATEST TORNADO THREAT WILL LIKELY EXIST NEAR
RETREATING WARM FRONT SWD INTO THE WARM SECTOR ACROSS THE ARKLATEX
REGION AND VICINITY.
WITH TIME...LOW IS FORECAST TO DEEPEN AND COLD FRONT WILL INTENSIFY.
INCREASING LINEAR CONVERGENCE SHOULD FAVOR AN EVOLUTION TOWARD A
SQUALL LINE DURING THE EVENING / OVERNIGHT. VERY STRONG /60-PLUS/
WINDS AT LOW LEVELS WILL SUPPORT A THREAT FOR WIDESPREAD /
POTENTIALLY SIGNIFICANT WIND GUSTS ALONG SQUALL LINE AS IT MOVES EWD
ACROSS THE LOWER MS VALLEY THROUGH THE END OF THE PERIOD.

http://www.spc.noaa.gov/products/outlook/day1otlk.html

Be careful down there...

[michaelwmoss]

This looks to be a very simliar situation to the storm last week. There is a HUGE upper low coming rapidly out of the 4 corners region. The Jet stream is screaming over this system as well.

While I do have to work part of the evening, I will try to be on the Teamspeak room, especially during the overnight, to track this situation.

[PurdueWx80]

Michael -

I think this outbreak will be in the TN & lower MS Valleys. The surface low will be bombing out in our neck of the woods, but it will be passing through the Ohio Valley/Midwest very late tonight. Not that severe weather isn't possible, but it is almost unheard of that late at night this far north (at this time of the year). Nonetheless, there will be heavy rain and thunderstorms associated with the powerful upper low as it moves over IN and IL tonight and in the morning. It feels like spring out there right now with temps and dewpoints in the 50's - time to open the windows and shut off the heat for a bit.

[therock1811]

Thats what worries me. The low will be passing here sometime after midnight tonight. Storms will probably be ongoing at that time. If we get enough lift, it could be a long night here.

[michaelwmoss]

Michael -

I think this outbreak will be in the TN & lower MS Valleys. The surface low will be bombing out in our neck of the woods, but it will be passing through the Ohio Valley/Midwest very late tonight. Not that severe weather isn't possible, but it is almost unheard of that late at night this far north (at this time of the year). Nonetheless, there will be heavy rain and thunderstorms associated with the powerful upper low as it moves over IN and IL tonight and in the morning. It feels like spring out there right now with temps and dewpoints in the 50's - time to open the windows and shut off the heat for a bit.

It's been a very unusal year thus far bro. But I agree with the assement. Again it is going to be a HUGE windmaker for us before and after the storm passes. Look for some Wind Advisories or even High Wind Warnings around the Midwest starting this evening

[PurdueWx80]

I was just looking at the regional WRF run at UI-Champaign and it shows 50-60 kt winds at 925 mb over IN and IL in the morning!!! If there is no squall line along the front, we could see gusts easily to 50 mph in the morning - if there is a surface-based squall line then your assessment would be correct and winds would be greater. I'm beginning to wonder now, given the fact that temps should be rising into the 60's overnight. This is just what I needed as I'm trying to finish up end-of-semester work.