2/24/2010 Storm Mode Questions

[Bill Tabor]

Concerning the tornado potential: Is anyone concerned with the 850/500mb crossover and lower level directional shear as this system moves east? So far that sucks and is unidirectional in eastern TX and ATM doesn't look much better further east. So far this is contributing to the squall formation. How are we going to stop the raging squall to get discrete cells, or are we simply hoping chase wise for embedded supercells in the squall?

 

[ahaberlie]

Question for you guys.. with the better CAPE/Instability in far SE Arkansas.. do you think we may see some sort of discrete cell formation ahead of the line in texas?

 

[Skip Talbot]

Prefrontal initiation is something you should always be on the look out. The question is, what's the source of lift? The models have been showing a pretty solid band maintaining itself through tonight. I believe the HRRR had two rather close squalls on its plots, but both looked pretty linear.

The current storms are definitely suffering, but I pretty much expected that as the low level winds are veered pretty badly and surface based instability is weak. Now, when the low level jet ramps up after dark and the low deeepens, winds are forecast to back at the surface by the MS river valley and the 850's strengthen significantly and even back a little. This is going to cause the helicity values to skyrocket. I believe the thinking is that there is potential for this line to actually break up into more discrete supercells after dark. Otherwise, yes, everything is going to be heavily embedded in that mess of a line. There's so much forcing from that trough going overhead that I imagine we'll still be looking a gigantic cluster of crapvection even after the sun goes down across eastern AR. Any storm that tries to go dominant may get choked off as a result. Looks like SPC is sticking to their guns, however.

 

[Skip Talbot]

Prefrontal initiation is something you should always be on the look out. The question is, what's the source of lift?

Well, it appears we've got some prefrontal activity in progress with small tornado warned cell in Tennessee. Looks like there might be a shortwave embedded in the main part of the trough that's moving out over the warm sector kicking up some new storms. 1km helicity is over 400 in this area so any storms that stay discrete should quickly become supercells.

 

[Steven Howell]

I was just looking at that cell in GR2AE.....nice cross section shows a funnel in the upper levels, not sure if it has reached the surface as of the latest scans....

 

[rdale]

nice cross section shows a funnel in the upper levels, not sure if it has reached the surface as of the latest scans....

Radar does not show a funnel, let alone one in the upper levels.

 

[Steven Howell]

perhaps I was looking at something different in the volumetric display in AE then? I stand corrected.

 

[Skip Talbot]

perhaps I was looking at something different in the volumetric display in AE then? I stand corrected.

Do you have a screenshot you can share with us so we can see what you're looking at? Nexrad radar(even level 2) cannot resolves features as small as a funnel. I'm guessing there was a funnel shaped chunk of reflectivity in the volumetric scan, which may describe the shape of some precipitation or downdraft. Funnels are associated with the updraft, and like the updraft would have a weak return on the radar, so if the radar could resolve it, you'd be more likely to see it as a hole rather than a solid object in the volumetric scan.

 

[Steven Howell]

ah..thanks for the clarification Skip....yes, it was a "funnel" shaped cone of reflectivity alot, and curved down...I might have been looking at the BWER actually, now that I think about it. I did a volumetric of the hook and RFD of the cell. Makes perfect sense now. It takes a while to get used to the cross sectional view of the cell and learning what the features are....