01/02/06: FCST: Ohio Valley and Southward

[SteveCarter]

MIXED LAYER CAPE AT OR ABOVE 1000 J/KG IS EXPECTED BY MONDAY AFTERNOON ACROSS MUCH OF GEORGIA AND ADJACENT AREAS OF ALABAMA/NORTHERN FLORIDA/ SOUTH CAROLINA. CAPE IS PRETTY GOOD FOR THIS TIME OF THE YEAR. I BELIEVE , BUT NOT SURE, THIS IS A BETTER FORECAST THAN YESTERDAY. STRONG DEEP LAYER SHEAR IN EXCESS OF 50 KT SHOULD PROVE FAVORABLE FOR ISOLATED SUPERCELLS, SO THINGS DO SEEM TO BE COMING TOGETHER. I WISH THE NEW UPDATES WERE ALREADY OUT, BUT TIME FOR BED. GETTING UP EARLY FOR MONDAY'S EVENT. SEE YA DOWN THE ROAD!!

 

[Brett Adair]

From BMX SPS...these are excerpts not the entire thing.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
737 AM CST SUN JAN 1 2006

ALZ011>015-017>050-011930-
AUTAUGA-BARBOUR-BIBB-BLOUNT-BULLOCK-CALHOUN-CHAMBERS-CHEROKEE-
CHILTON-CLAY-CLEBURNE-COOSA-DALLAS-ELMORE-ETOWAH-FAYETTE-GREENE-HALE-
JEFFERSON-LAMAR-LEE-LOWNDES-MACON-MARENGO-MARION-MONTGOMERY-PERRY-
PICKENS-PIKE-RANDOLPH-RUSSELL-SHELBY-ST CLAIR-SUMTER-TALLADEGA-
TALLAPOOSA-TUSCALOOSA-WALKER-WINSTON-
737 AM CST SUN JAN 1 2006

HOWEVER...THE MOST IMPRESSIVE UPPER LEVEL DYNAMICS WITH THIS STORM
SYSTEM WILL NOT ARRIVE UNTIL LATER THIS EVENING AND TONIGHT. THIS
WILL CREATE THE POTENTIAL FOR ANOTHER ROUND OF STRONG TO SEVERE
THUNDERSTORMS IN CENTRAL ALABAMA SUNDAY EVENING INTO MONDAY. DAMAGING
STRAIGHT LINE WINDS...LARGE HAIL AND ISOLATED TORNADOES ALL LOOK
POSSIBLE LATE SUNDAY EVENING...BEGINNING AROUND 9 PM FOR WESTERN
ALABAMA...AND LASTING THROUGH MONDAY AFTERNOON FOR SOUTHEASTERN
ALABAMA. AT THIS TIME...THE AREA MOST LIKELY TO EXPERIENCE THE WORST
DAMAGING WEATHER WITH THIS SECOND ROUND OF SEVERE STORMS WILL BE
ALONG AND EAST OF THE INTERSTATE 65 CORRIDOR.

THIS STORM SYSTEM HAS THE POTENTIAL TO BECOME DANGEROUS VERY QUICKLY.
ALL OF CENTRAL ALABAMA SHOULD REMAIN ALERT AND MONITOR THIS SYSTEM
VERY CLOSELY AS IT CONTINUES TO DEVELOP.

I will be chasing across AL/GA also tomorrow. For an exchange of numbers just hit me with a PM and we will meet up possibly. We are ready and equipped with GPS/mobile net and video equip. Time for a good SE storm chase.

 

[Howard Robinson]

Guys good luck tomorrow. I do need to warn anyone who is going to chase, that most systems like this come in during the early evening hours. It may be dark by the time these systems move into Georgia. Highway I-85 is not the best highway to chase on, also you have to consider Atlanta is one huge heat island. I have seen systems come in like this only to die out when they hit the heat island of Atlanta. If anything is going to drop, it most likey be in the Northern 'burbs or over to western parts of Metro Atlanta.


Just a side note, I'm a little worried for my family that is in Atlanta. This is not looking good for Metro and have warned as many of them as I can.


Howard Robinson

 

[Bill Hark]

This situation is looking more interesting (and dangerous to the residents). According to the latest Eta (init 12Z Jan1), there is now more backing of the winds through northern GA, extreme eastern TN and KY, western NC for 18Z. This also corresponds to precip. The tongue of increased CAPE and LIs to -6 lags behind a bit from central Alabama through central TN and KY. It is only by 00Z that this area has shifted into northern GA. The GFS shows more of a concentrated area of precip over northern GA at 18Z and it is more in sync with the northward extension of high dewpoints.

If I had the luxury to chase, I'd set up camp tonight in Dalton, GA (extreme nortwest part of the state) for Monday's chase. From my maps,t hat looks like a crappy chase country with mountains and poor E-W road. This is a situation where one would need XM or very good nowcasting to stay out of danger with these fast moving storms. I am also concerned about the onset of darkness before the storms move further east.

Of course, this is closer to Virginia. I'll check data late this afternoon and reconsider...

Bill Hark
http://www.harkphoto.com

Addenda: I hope there are some folks chasing today. Sometimes there are nice tornadoes BEFORE the main outbreak day.

 

[Angie Norris]

Well, a few changes (as I see it :wink: ) from last night. The shear is still there through the day tomorrow, with the best dynamics still over southern TN southward into southeast AL then eastward into central GA. Interesting little CAPE spike of 1500-2500J/kg at 18Z in central AL running north into central TN and KY then shifts east into northwest GA/southern TN at 0Z. Still a decent bit of CAPE ~1000J/kg into eastern TN and KY at 0Z. The "dryline" of yesterday has "morphed" into a cold front...which it prolly was yesterday (well, it looked like a dryline...my bad), with the warm front setting up near southern IL and IN...cold front trails back into MO and AR. A significant amount of precip looks to override the warm front into northern IN into MI.
I'm thinking we're dealing with two rounds of storms and two areas of storms... number one round south tonight...MS/AL/central TN into east TN. Not a strong tornadic potential tonight...just rain, hail, wind...the usual stuff. Then tomorrow...maybe slight tornadic potential south of the warm front (IN/OH), with the main show being tomorrow afternoon/early evening in southern TN (Chatanooga area) southward into northeast and central AL, then eastward into central GA. with the best shear/ upper dynamics being in that area. East TN and KY may be somewhat capped IF cloud cover from tonight's storms doesn't erode. However, if any clearing occurs, all bets are off...storms will explode in that area.
Anybody going out tomorrow...be careful and enjoy the early season offerings. These things will be speed racers. If I didn't have to work, I'd make the drive back east and play in my old playground.
Angie

 

[Brett Adair]

I will be chasing from 3pm this afternoon through the duration of the event. Also...this thing looks better south of I-20 and East of 65 with a better backed SFC profile pretty much over my house for tonight through midday tomorrow. This thing is still very much a dryline attm btw....looks to stay that way to me.

 

[SteveCarter]

Dalton is a horrible place to set up, and if you decide to take Hwy 76 from there, forget it. Hwy 76 winds, twists, and runs through nothing but mountains all the way to my house in Seneca, SC. I use THAT road to get to I-75, when I want to avoid Atlanta, and go "scenic". Really guys...ANYTHING North of I-85, from Atlanta East is TO MOUNTAINOUS to chase! Flat as a pancake from Athens south to Macon, and several pretty good roads, including 441S from Watkinsville. ***Local Atlanta - Greenville, SC forecast are saying that the BULK of the storms will be here around 1PM Monday, and last through Monday eve. Amazing how serious the weather forecasters are taking this potential weather situation. They really are warning everyone, so I hope people take notice.

 

[Howard Robinson]

Dalton is a horrible place to set up, and if you decide to take Hwy 76 from there, forget it. Hwy 76 winds, twists, and runs through nothing but mountains all the way to my house in Seneca, SC. I use THAT road to get to I-75, when I want to avoid Atlanta, and go "scenic". Really guys...ANYTHING North of I-85, from Atlanta East is TO MOUNTAINOUS to chase! Flat as a pancake from Athens south to Macon, and several pretty good roads, including 441S from Watkinsville. ***Local Atlanta - Greenville, SC forecast are saying that the BULK of the storms will be here around 1PM Monday, and last through Monday eve. Amazing how serious the weather forecasters are taking this potential weather situation. They really are warning everyone, so I hope people take notice.

Steve is right, I wouldn't chase on North I-85, avoid North I-75 as well.
441S is a good flat road, but be sure you have a lot of gas, as there are not a lot of places to get gas on that road once you get past Madson.

 

[Scott Olson]

Now that there seems to be some agreement with the models.
I'd chase the secondary WF in in NE GA. Instability should rise steadily throughout the day and should be at least 1K J/KG by mid-afternoon. There is a marked increase in low level directional shear (the kind that supports strong tornadoes) along this boundary as well as increased lift. Areas as far north IN, OH have potiental for tornadoes as well but I believe that N GA will have an increased risk with 0-3km SRH POS HELICITY OF 500+ m2/s2. Much deeper moisture avaliable as well in GA and AL.

 

[Bill Hark]

Special Weather Statement

http://www.erh.noaa.gov/showsigwx.php?warn...ather+Statement

January and they are using this wording, "STRONG AND DAMAGING TORNADOES WILL BE POSSIBLE."

They seem to be predicting the formation of a mesolow

"POSSIBILITY OF A SECONDARY LOW PRESSURE AREA FORMING OVER NORTHEAST GEORGIA AND THE WESTERN CAROLINAS."

From my experience on the Plains, predicting the formation of a mesolow is difficult until the day of the event, usually using real time data. Looking at the current model outputs, I don't see it. Maybe a hint on the Eta if I use my imagination. Anybody see what I am missing?

A mesolow may cause one to have to decide between two targets: Just to the east/northeast of the mesolow or along the warm front.

Bill Hark

 

[Mike Johnston]

They seem to be predicting the formation of a mesolow

"POSSIBILITY OF A SECONDARY LOW PRESSURE AREA FORMING OVER NORTHEAST GEORGIA AND THE WESTERN CAROLINAS."

From my experience on the Plains, predicting the formation of a mesolow is difficult until the day of the event, usually using real time data. Looking at the current model outputs, I don't see it. Maybe a hint on the Eta if I use my imagination. Anybody see what I am missing?

Bill Hark

Yes, when I saw this mention of a secondary low in conjunction with the anticipated southern Atlantic coast event tomorrow evening, I was a little confused as nothing was obvious on the model maps. Even more confusing (to me, at least) was the pronounced region of subsidence/cooler temperatures which seems to "wedge" down through the Piedmont in advance of the system, with persistence of instability and theta-e axis remaining to the west of the Appalachians even after the passage of the surface wind shift line. So...I checked out some of the AFD's and ran across a term in the Greenville-Spartanburg discussion which I had never heard of before: "In-Situ Wedge."

From a weather glossary, In-Situ Wedge defined as:

Primarily refers to an elongated area of shallow high pressure at the earth's surface. It is generally associated with cold air east of the Rockies or Appalachians. It is another name for a ridge, ridge line, or ridge axis.

The Greenville-Spartanburg AFD mentions that this in-situ wedge may act as the surface boundary for convection, with a high degree of uncertainty re: both its location and strength. Perhaps these hints of a mesolow involve some kind of surface pressure gradient dynamics associated with this in-situ wedge? I'm far from qualified to form any hypothesis here, but any input from some of our more experienced forecasters on the board would be appreciated.

 

[Scott Olson]

That's the secondary warm front in NE GA/CAROLINAS. Bill's right the formation of a meso-low is hard to forecast but if one was to form that would an area where I could see it occuring.

 

[nickgrillo]

--> http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=klvx (LVX at 18z)
--> http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=kcha (KCHA at 21z)

Both soundings show thermodynamic/wind profiles highly favorable for supercells and tornadoes. At 18z at Louisville, lifting a SB parcel yeilds over 2200 j/kg of CAPE (with about 300j/kg of 0-3km MLCAPE) with a nearly dry adiabatic lapse rate from the sfc-2km layer. On the KCHA sounding, winds are slightly backed at the sfc at 21z (slightly increasing low-level shear) while the KLVX sounding shows a SSW sfc flow. BL-6km vertical shear is highly favorable for sustained supercells (nearly 60knts) given strong speed shear throughout the trophosphere and decent veering within the lower levels. A weak inversion on the KCHA sounding at 18z (30 hr) is completely eroded by 21z, while the KLVX sounding shows no inversion as early as 18z.

 

[Fred Gossage]

They seem to be predicting the formation of a mesolow

"POSSIBILITY OF A SECONDARY LOW PRESSURE AREA FORMING OVER NORTHEAST GEORGIA AND THE WESTERN CAROLINAS."

From my experience on the Plains, predicting the formation of a mesolow is difficult until the day of the event, usually using real time data. Looking at the current model outputs, I don't see it. Maybe a hint on the Eta if I use my imagination. Anybody see what I am missing?

Bill Hark

Yes, when I saw this mention of a secondary low in conjunction with the anticipated southern Atlantic coast event tomorrow evening, I was a little confused as nothing was obvious on the model maps. Even more confusing (to me, at least) was the pronounced region of subsidence/cooler temperatures which seems to "wedge" down through the Piedmont in advance of the system, with persistence of instability and theta-e axis remaining to the west of the Appalachians even after the passage of the surface wind shift line. So...I checked out some of the AFD's and ran across a term in the Greenville-Spartanburg discussion which I had never heard of before: "In-Situ Wedge."

From a weather glossary, In-Situ Wedge defined as:

Primarily refers to an elongated area of shallow high pressure at the earth's surface. It is generally associated with cold air east of the Rockies or Appalachians. It is another name for a ridge, ridge line, or ridge axis.

The Greenville-Spartanburg AFD mentions that this in-situ wedge may act as the surface boundary for convection, with a high degree of uncertainty re: both its location and strength. Perhaps these hints of a mesolow involve some kind of surface pressure gradient dynamics associated with this in-situ wedge? I'm far from qualified to form any hypothesis here, but any input from some of our more experienced forecasters on the board would be appreciated.

This is the scenario I mentioned in this thread last night when the 00Z NAM rolled in.

 

[Robert Balogh]

If anyone is interested

I am in Athens Ga and am gonna try and follow stuff tomorrow afternoon. Write me at [email protected] or call me on my cell 706-207-0227.

A word of warning for anyone that does chase. The country here is not optimal, to put it mildly. I know the back roads pretty well and think the best bet might be to park on a hillside and watch stuff go by as opposed to trying to chase

I'm not any kind of forecaster, but I'd definately go for stuff along the warm front - down here the main front will almost always develop into a fast moving squall line, sure there will be supercells embedded in it but good luck getting in to have a look

An amateur opinion, but if I were driving in from somewhere else to follow this event, I'd park it in Augusta tonight and then be in decent position to move towards anything that happens along the trailing edge of the warm front 3-6PM ish without having to go thru iot to get at it

I think Elberton Ga - Hartwell Ga - Anderson SC - Greenwood SC is gonna be your rectangle wherein somethin's gonna touch down. We'll see