11/28/05 NOW: OH & TN Valleys

[Sam Sagnella]

Line of severe thunderstorms with embedded supercells is ongoing across AL/TN at this time, and as I write this damage reports are just beginning to come in from north of Birmingham with a reported tornado ongoing in Blount County. SPC Mesoanalysis indicates generally 250-1000 J/Kg sbCAPEs across central and northern Alabama with 0-1km shear running around 35-40kt. 0-1km SRH is also maximized from central TN southward into NErn AL where values are exceeding 600m2/s2 in some areas! Narrow band of clearing now exists immediately ahead of the eastward progressing line of storms, so with strong dynamics already in place and instability on the increase, the tornado threat definitely appears to be significant.

EDIT: Intense low-level velocity couplet becoming better defined to the W of the Birmingham metro area with a TOR just issued; western/northwestern suburbs of the city are facing an immediate threat from a tornado.

EDIT2: This storm has developed an appendage and still exibits strong low-level rotation ....latest LSR indicates a wall cloud with an associated funnel near Hueytown. It should stay to the west of I-20 which is good news for the major population center, but the airport is in the immediate path.

 

[Gabe Garfield]

Sam, I agree about the significant threat for tornadoes, with the only caveat being the the storm mode. For the moment, though, scattered thunderstorms/supercells is the mode. If it remains like this for a while, I see no reason why a few tornadoes (some possibly significant) shouldn't develop in this region.

What I like about today:

1. STRONG shear. Deep-layer shear easily about 50 kts across the area of interest. Also, surface winds are backed out of the southeast, which is increasing the low-level shear (0-1 km helicity >400 m2/s2).

2. Insolation. As Sam mentioned, there is a nice cloud-free area in advance of the developing thunderstorms, so instability will be maximized in these areas.

3. Rich moisture. Unlike yesterday, today has the advantage of richer moisture (Tds >65 in some locations) and correspondingly lower LCLs.

Gabe

 

[Sam Sagnella]

If this storm hasn't produced a tornado yet, it is VERY close. NBC13 in Birmingham has streaming video, which I am watching audio-less in the computer lab LOL.

AT 250 PM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO SHOW A STORM WITH STRONG ROTATION NEAR THE TOWN OF MINOR...AND LOCAL TELEVISION HAS SHOWN LIVE PICTURES OF A ROTATING WALL CLOUD. THIS STORM COULD PRODUCE A TORNADO AT ANY TIME.

 

[Andrew Khan]

I might go west a bit, and see what I can get. I'm hoping to intercept an embedded supercell, and get some nice hail. IT should reach my home town, soon.

 

[Andrea Griffa]

Impressive supercell in Bibb county with TVS...

http://forum.meteonetwork.it/attachment.ph...14&d=1133214559

 

[Matt Haworth]

Another supercell in eastern Bibb county with a TVS. The storm tracker on my radar has had a TVS on this storm for the past 6 scans.

Base Reflectivity
http://weather.xonelabs.com/BMX%200.5%20Ref.png

Storm Track
http://weather.xonelabs.com/BMX%20Storm%20Track.png

 

[nickgrillo]

While instability is nearly non-existant across MI, the forcing along the cold front has been enough to initiate thunderstorms. Deep-layer shear very much supports long-lived updrafts, while extreme low-level shear will support a threat for an isolated tornado or two with any sustained storms, and a few of the storms across western MI have been showing some decent low-level rotation now and then, per GRR radar.

 

[Robert Dewey]

While instability is nearly non-existant across MI, the forcing along the cold front has been enough to initiate thunderstorms. Deep-layer shear very much supports long-lived updrafts, while extreme low-level shear will support a threat for an isolated tornado or two with any sustained storms, and a few of the storms across western MI have been showing some decent low-level rotation now and then, per GRR radar.

I haven't checked any soundings, but I'm surprised we haven't seen any SVR warnings. Winds just off the SFC are rather strong, and L2 data is showing 55-58 DBZ cores... Time to go check soundings and see if there is a rock solid inversion ........

EDIT: Appears that things are slightly elevated at 3K FT...

 

[nickgrillo]

While instability is nearly non-existant across MI, the forcing along the cold front has been enough to initiate thunderstorms. Deep-layer shear very much supports long-lived updrafts, while extreme low-level shear will support a threat for an isolated tornado or two with any sustained storms, and a few of the storms across western MI have been showing some decent low-level rotation now and then, per GRR radar.

I haven't checked any soundings, but I'm surprised we haven't seen any SVR warnings. Winds just off the SFC are rather strong, and L2 data is showing 55-58 DBZ cores... Time to go check soundings and see if there is a rock solid inversion ........

Current mesoanalysis shows very weak CINH across westcentral MI, with muCAPE slowly building across the area. An area of low-level rotation keeps wanting to tighten itself over White Cloud the past couple of scans.

 

[Andrew Khan]

I'll be surprised if the Storm in Autauga County, AL does not produce a tornado, or has not in the recent past.

 

[Brett Adair]

I was on the storms in Coosa/Bibb/Shelby Counties and do have pictures of the rotating wall cloud. There were actual touchdowns in Bibb/Coosa/Jefferson/Autauga County. The storm we caught up with in Coosa County near Equality produced an F-1 tornado. Pics later....