Archive Severe threat April 26-27, 2011

[TW Archive]

NorthGaWeather
Posted 24 April 2011 - 10:05 PM

69hr NAM sounding for KHSV is impressive!

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:09 PM

ARCC, on 24 April 2011 - 09:58 PM, said:

Uh oh, big change on the NAM, forms a secondary slp behind the main one. Could be a huge concern if it keeps sfc winds backed longer.

That's actually been there for multiple runs of the NAM and GFS. We're not going to need the surface winds backed much more than they are already.... the 850-mb and up winds are trending more veered... which is doing the same thing that backing the surface winds would do. The forecast hodographs are now displaying the classic sickle configuration, with the rightward 90 degree kink at around 1 kilometer.

 

[TW Archive]

kbh_81
Posted 24 April 2011 - 10:11 PM

Fred Gossage, on 24 April 2011 - 10:09 PM, said:

That's actually been there for multiple runs of the NAM and GFS. We're not going to need the surface winds backed much more than they are already.... the 850-mb and up winds are trending more veered... which is doing the same thing that backing the surface winds would do. The forecast hodographs are now displaying the classic sickle configuration, with the rightward 90 degree kink at around 1 kilometer.

say what?

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:13 PM

kbh_81, on 24 April 2011 - 10:11 PM, said:

say what?

We don't need the surface winds to back southeasterly in this case... because the winds above the surface are getting a more southwesterly component. We're still increasing low-level directional shear.

 

[TW Archive]

ARCC
Posted 24 April 2011 - 10:13 PM

Fred Gossage, on 24 April 2011 - 10:09 PM, said:

That's actually been there for multiple runs of the NAM and GFS. We're not going to need the surface winds backed much more than they are already.... the 850-mb and up winds are trending more veered... which is doing the same thing that backing the surface winds would do. The forecast hodographs are now displaying the classic sickle configuration, with the rightward 90 degree kink at around 1 kilometer.

I see that you are right. Haven't paid much attention to the models over the past day or so, been too busy.
Edited by ARCC, 24 April 2011 - 10:47 PM.

 

[TW Archive]

weatherguy
Posted 24 April 2011 - 10:14 PM

Numbers already coming up fast on the new 21z run SREF for Wednesday:

21z run SREF does show a more robust secondary low compared to the 15z run for 15z Wed.:


21z SREF Significant Tornado Parameter, very ominous (between 6 and 8), and very high for 66 hours out:

 

[TW Archive]

kbh_81
Posted 24 April 2011 - 10:14 PM

which means the longer the worse?

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:15 PM

kbh_81, on 24 April 2011 - 10:14 PM, said:

which means the longer the worse?

The increasing directional shear in the low-levels means that tornadoes are a higher threat. I was just pointing out that what ARCC was looking for... in order for that to happen.... was happening by other means.

 

[TW Archive]

tennessee storm chaser
Posted 24 April 2011 - 10:17 PM

Fred Gossage, on 24 April 2011 - 10:09 PM, said:

That's actually been there for multiple runs of the NAM and GFS. We're not going to need the surface winds backed much more than they are already.... the 850-mb and up winds are trending more veered... which is doing the same thing that backing the surface winds would do. The forecast hodographs are now displaying the classic sickle configuration, with the rightward 90 degree kink at around 1 kilometer.

fred, on the 0z nam tonight. does the memphis area still get in the warm sector or will the second low chokes it off. whats your thoughts for west tn on that run, thanks fred

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:18 PM

tennessee storm chaser, on 24 April 2011 - 10:17 PM, said:

fred, on the 0z nam tonight. does the memphis area still get in the warm sector or will the second low chokes it off. whats your thoughts for west tn on that run, thanks fred

The placement of the secondary surface low does keep the warm sector out of most of the Memphis metro area... possibly even out of your area... by the heat of the day Wednesday. I know that you are questioning something that Kevin T. wrote on TNWX. My personal advice to you is to not do that...

 

[TW Archive]

tennessee storm chaser
Posted 24 April 2011 - 10:20 PM

Fred Gossage, on 24 April 2011 - 10:18 PM, said:

The placement of the secondary surface low does keep the warm sector out of most of the Memphis metro area... possibly even out of your area... by the heat of the day Wednesday. I know that you are questioning something that Kevin T. wrote on TNWX. My personal advice to you is to not do that...

i agree with the later fred, thanks

 

[TW Archive]

RollTide18
Posted 24 April 2011 - 10:23 PM

Where does this leave the southern AL/MS area?

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:24 PM

RollTide18, on 24 April 2011 - 10:23 PM, said:

Where does this leave the southern AL/MS area?

I think you're going to be under the gun again Wednesday.

 

[TW Archive]

trency911
Posted 24 April 2011 - 10:29 PM

Sorry for the IMBY question Fred, but how do you think this will play out for the Atlanta area?

 

[TW Archive]

Fred Gossage

Posted 24 April 2011 - 10:30 PM

trency911, on 24 April 2011 - 10:29 PM, said:

Sorry for the IMBY question Fred, but how do you think this will play out for the Atlanta area?

Things will probably be lining out by that time... but I still wouldn't rule out isolated tornadoes. Unless something changes... like mesoscale issues from north AL stuff Tuesday night... your main threat may be a linear configuration with damaging winds and isolated tornadoes.

 

[TW Archive]

ALhurricane
Posted 24 April 2011 - 10:32 PM

Fred Gossage, on 24 April 2011 - 10:24 PM, said:

I think you're going to be under the gun again Wednesday.

To me it looks like another day of numerous discrete supercells with the potential for long tracked tornadoes. Very similar to April 15th with the best parameters just shifted slightly further to the north.

 

[TW Archive]

SD
Posted 24 April 2011 - 10:34 PM

Fred Gossage, on 24 April 2011 - 10:30 PM, said:

Things will probably be lining out by that time... but I still wouldn't rule out isolated tornadoes. Unless something changes... like mesoscale issues from north AL stuff Tuesday night... your main threat may be a linear configuration with damaging winds and isolated tornadoes.

if you believe the NAM sim reflectivity its already collapsing at that point. NAM is keeping a relative dewpoint min across Ga and the western Carolinas again. Since this isnt a wedge situation you have to wonder what its trying to hint at. Theres plenty of hours of sfc flow off of the Atlantic/Gulf to moisten the BL but the model never does. The GFS is much more moist in Ga...things that make you say hmm

 

[TW Archive]

mwbwhorton
Posted 24 April 2011 - 10:34 PM

im guessing northern louisiana is in the crapper at the moment if areas of southern miss,and alabama look bad.....and that memphis may stay out of the warm sector alarms me greatly....
Edited by mwbwhorton, 24 April 2011 - 10:37 PM.

 

[TW Archive]

Fred Gossage
Posted 24 April 2011 - 10:38 PM

mwbwhorton, on 24 April 2011 - 10:34 PM, said:

im guessing northern louisiana is in the crapper at the moment if areas of southern miss,and alabama look bad.....and that memphis may stay out of the warm sector alarms me greatly....

Geographically speaking, I think that 30% contour on the SREF graphic a couple posts up.... nicely outlines the greatest risk area for the day on Wednesday. I think you're very much in the game Tuesday and Tuesday night.

 

[TW Archive]

iceman83
Posted 24 April 2011 - 10:42 PM

Guys kind of late to the game but what are we looking at in NE Arkansas the next couple of days? Thanks for any input and stay safe.
Edited by iceman83, 24 April 2011 - 10:43 PM.