3/21/2007 FCST: TX / OK / KS / NE / IA

[Chris Allington]

Now that clearing is arriving and mixing is a little stronger we seem to be trying to mix out a little bit. Went from 70/58 to 73/57 here in Lincoln. Mesoanalysis seems to be trying to portray an area of weakening, or atleast reduced CIHN over East Central Nebraska, west of Omaha.

 

[bbarjenbruch]

While the cap may be a problem today, the veered winds are definitely not. If you look at the forecast hodographs, with an ESE storm motion (right-moving supercell here), SW 850 flow and SSW surface flow are more favorable than if it were backed. Streamwise vorticity at low-levels will be maximized under this "veered" low-level flow scenario.

But if a storm doesn't fire and move away from the front, then it won't matter anyway.

Agreed. The hodographs are still giving over 100m2/s2 0-1 helicity at initiation. Up to 150 in some cases. Also, just looking at the most recent RUC runs, any cap is completely eroded by 5 PM local time. I'm not necessarily sure that it's a good thing as it may go more linear, but oh well... in the end I think we'll have storms for sure. Of more worry to me is that we do seem to be mixing out slightly... uh oh

 

[J.B. Dixon]

FYI -- For those looking at the Hastings Nexrad for visuals of the boundaries, don't be fooled by the returns right along the Platte River between Kearney and Grand Island, as it's most likely picking up Sandhil Crane traffic......it's about the peak of their annual migration through that stretch of the river (The Nebraskans know what I'm talking about...lol)

 

[Daniel Christianson]

While im still hauling trash i should be off work soon i plan on sitting around the omaha area for a bit but will be playing the cold front.. i hope all us chasers get some action, i see were mixing a bit too.. but im not too concerned have a good one all.

 

[Michael O'Keeffe]

Sitting at the Concordia Super 8 waiting for intiation. Winds are strong out of the south and skies are clear and blue. There is a bit of mixing, but it is not hurting the dewpoints to drastically. Will sit tight here and wait for initiation which will be sometime after 4pm. I'm hoping something will fire and produce a few naders, the dryline/cold front intersection is still a little ways a way.

Good luck to everyone today!

 

[Jim Bishop]

While the cap may be a problem today, the veered winds are definitely not. If you look at the forecast hodographs, with an ESE storm motion (right-moving supercell here), SW 850 flow and SSW surface flow are more favorable than if it were backed. Streamwise vorticity at low-levels will be maximized under this "veered" low-level flow scenario.

But if a storm doesn't fire and move away from the front, then it won't matter anyway.

I'm sure hodographs might look pretty impressive with the veered surface winds given the veered 850mb to 500mb flow. But veered surface winds ARE a big problem today.

The veered nature of the low level flow will both 1)increase the cap and 2)mix out the low level moisture, which will actually further aid in keeping storms from firing.

Just look at the surface dewpoints over North Central Kansas & Southern Nebraska. Winds have been out of the south to south-southwest all day at 10-25 knots. Yet the dewpoints haven't gotten above 59. If anything they've been slowly decreasing to 55-58 and so on.

As you stated you need to get a storm first, but it also has to be one that's not struggling with the cap. I don't believe that will occur today in Kansas or Nebraska, so talking about the veered surface winds aiding in streamwise vorticity seems pointless.

 

[Craig Maire II]

I to see that the DP's are mixing a bit but I don't think that DP's between 55 and 58F are much of a drop from 59F I'm sitting in the town of Friend right now approximately 40 west southwest of Lincoln and am pretty positive I'll witness some severe weather later today, not sure if I'll see a tornado but I'll be happy just to see a shelf cloud, storm stucture, large hail and or damaging winds let alone a beautiful wall cloud or tornado I'm not to picky Seems like the farther away some people live from an area of expected storms the worse the settup is . Remember all it takes is 1 supercell to make a chaser's day; one doesn't necessarily need a massive severe weather outbreak to have a great chase

 

[bbarjenbruch]

While the cap may be a problem today, the veered winds are definitely not. If you look at the forecast hodographs, with an ESE storm motion (right-moving supercell here), SW 850 flow and SSW surface flow are more favorable than if it were backed. Streamwise vorticity at low-levels will be maximized under this "veered" low-level flow scenario.

But if a storm doesn't fire and move away from the front, then it won't matter anyway.

Sorry, I should elaborate on my previous post. I agree with both Mr. Timmer and Mr. Bishop that although we have a more westerly component to our winds, the low level helicity is still adequate. I also know that it will also aid in the mixing out of some moisture (hind sight is always 20/20, haha) which in turn makes it a little harder to break that cap. In the end, I'll be looking for a supercell or two, but in order to even get those, I think this frontal boundary is going to have to ease up a little bit and wait for the slightly better mid/upper level winds to arrive. We'll see what happens.

 

[Jim Bishop]

Craig, I was just saying the dewpoints should at least be steady if not increasing (given the southerly flow), but instead they are mixing out slightly. Also, the cap might break up there along the cold front. But I'm just not convinced that if a storm fires it will be tornadic, since it will likely be struggling with the cap, and could have a dangerous interaction with the cold front. I suppose that leaves the possibilty for a nice lp supercell. Best of luck to you!

 

[Craig Maire II]

Today

Thanks Jim Sorry if I sounded rude, guess I'm a little biased right now since I drove all the way from Waterloo Iowa to see some storms today

 

[Jim Bishop]

Well I just noticed the 18z Omaha sounding. The convective temperature is 91 degrees. With current temps in the mid to upper 70s, you're gonna need some upper support to break that cap. Either that amazing forcing along the cold front!

Seems like the cap has a much better chance of breaking down in the southern Texas Panhandle along the dryline. Surface and 850mb winds are much more backed, and the depth of the moisture is greater. Another good point is lower concentration of upper clouds. This areas is iffy, but seems more probable than the northern target.

 

[Adam Atkins]

Nice dry punch/dryline bulge in NW Oklahoma occuring currently and some high based Cu I imagine, which are showing up fairly consistently on visible sat, have developed and of course...have been beaten down by the cap. Strong surface convergence might not be enough with shortwave ridging aloft and weak mid-level vorticity advection. Surface parameters are nicer south, but the cap is stronger. Also low level flow is not as veered as the northern edge along the front. I highly doubt any storms are going to fire along the DL though. This reminds me more of a marginal May or June setup than a typical dynamics dominated March event.

 

[Reed Timmer]

The cumulus here east of York is beginning to tower.

Earlier, my comment was on the favorable kinematics...not the thermodynamics.

Reiterating...the hodographs here to the north with ESE storm motion are more favorable with SW 850 and SSW surface...not the backing that is always assumed favorable. One must analyze the hodo to determine if backing will help in tornadogenesis. In this case in southeast NE, it won't.

Well...I need to end this...I think I just spotted an EF-5.

 

[Craig Maire II]

Storms developing northwest and north of Lincoln