6/20/06 NOW: MN / IA / WI / NE / CO / KS

[Kurt Hulst]

Sitting in Ames IA. Trying to stick along the warm front at the moment New MD for the Northern Iowa and southern MN area. Watch may be issued if convection can organize. So Just watching trends. The CU out to the west doesnt look like much of a Cu field kinda thined out and moved away from Soiux City. Convection initiating along the IA and MN border. Not to far from it but being patient.

Good Luck to any one out

 

[David Draun]

Wow! That cap is still insanely strong. It seems the strong heating required to break it did not occur. And I thought that cap would go easily this afternoon, boy was I wrong. This looks to be an entirely nocturnal MCS event, perhaps elevated. This sucks too, because LCL's are in the 800-1200m range. Mesoanalysis does show a hole in the CINH over west central IA. The cap looks to be killing those showers in southern MN though. But those showers may be all that's needed to weaken the cap further. It sure is getting late however. Happy hunting!

 

[Sean McMullen]

I keep going over the meso analysis page and it seems all the parameters are in place for something aweful to happen around nw IA, sw MN right now, also CINH has dramatically dissapated over nw IA. What am I missing that could explain why nothing is happening there?

EDIT: Sorry, I started writing this post while David was posting his reply, in case you're wondering. But I'm a little confused, how could CINH be gone with a strong cap in place, could someone help me out here?

 

[nickgrillo]

I keep going over the meso analysis page and it seems all the parameters are in place for something aweful to happen around nw IA, sw MN right now, also CINH has dramatically dissapated over nw IA. What am I missing that could explain why nothing is happening there?

EDIT: Sorry, I started writing this post while David was posting his reply, in case you're wondering. But I'm a little confused, how could CINH be gone with a strong cap in place, could someone help me out here?
[/b]

Sean,

David was referring to the area of weakened CINH (per SPC mesoanalysis) across western IA (as you mentioned yourself). There is still an inversion layer (weakened in some spots) across much of the warm sector, nonetheless, mesoanalysis has shown a weakening trend in CINH the past couple of hours; mainly across western IA (and sw/sc MN) due to surface diabatic heating. However, CINH has yet to erode enough to allow for parcels to reach their LFCs (as indicated by those weak thunderstorms in southern MN earlier which were ripped apart and got their inflow 'chocked' off by the capping, since air was too negatively buoyant to be brought to its LFC).

 

[Jeff Snyder]

If CINH is gone, there is no cap. The 0z OAX sounding shows that the cap is pretty weak, and likely nearly nonexistant in areas where the dewpoints are >70F (in other words, in western IA). The wind profile looks very favorable for supercells, and the degree of low-level shear (adjust the 800-700mb winds up 5-15kts given stronger LLJ to the east of OAX) and moderate LCL heights (in IA, where Tds are >70F again) still suggest a threat of a strong tornado or two for any supercell in the threat area the next few hours. I think the 59kts 0-6km shear on the OAX is greater than the 0z RUC mesonalysis too. Regardless, I'm a little surprised we're not at least seeing a decent cu field based on that 0z OAX sounding. Again, the thermo profile looks nice in western IA if you adjust the 0z OAX sounding for low-70 dewpoints. The kinematic profile looks very favorable for supercells and tornadic supercells, though the threat is entirely conditional (and meeting the condition -- initiation -- is looking less likely with time).

 

[David Draun]

The LI values in western IA are very low, right where that weakened CINH is. SBCAPE is also at 4000 J/kg. Double digit supercell composites are rampant. What is preventing development there? Is it lack of forcing, decrease in heating due to the onset of nighttime, or something else? I do see high clouds on the satellite imagery. The 1 km EHI's are as high as 4! If something goes, it could be big one.

 

[Benjamin Sipprell]

RUC model initializations are showing minor ridging at 700 and 500 mb levels. Isn't it possible that such a weak ridging pattern at upper levels, though discrete, could lead to subsidence through the lower layers as well? It would surely answer the dissipation of the Cu field.

Just a thought.

 

[Joel Wright]

Hearing some slow rumbly thunder here in NW IL beneath the weak elevated convection.

Visible satellite in the waning light of day still shows absolutely no cumulus in the western half of IA. Like mentioned above I'm very surprised, especially with the amount of LL moisture and the leftover boundaries from earlier today.

 

[Jeff Snyder]

RUC model initializations are showing minor ridging at 700 and 500 mb levels. Isn't it possible that such a weak ridging pattern at upper levels, though discrete, could lead to subsidence through the lower layers as well? It would surely answer the dissipation of the Cu field.

Just a thought.
[/b]

The 21z RUC run showed a compact vort max located in southern IA, moving into IL. DNVA would be occurring on the back side of this departing vort max, which means that western IA would be seeing large-scale subsidence in its wake. This vort max is a seperate feature from the strong vort max that came through IA earlier this morning and helped induce the widespread convection earlier.

 

[rdale]

TAMDAR soundings showing a significant inversion around 875-825mb across southern MN / western WI (nothing out of Iowa lately.)

 

[Brian Stertz]

Yes very much in agreement Benjamin and Jeff..there was a large degree of subsidence behind that morning wave with 700mb temps rising and very little 500mb cooling. The 12 degree 700mb temps on the SPC Mesoanalysis indicate that the nasty subsidence has shifted eastward almost to the Mississippi River. Some slight mid-level cooling was sagging into N.Nebraska and SE South Dakota. Today is one of those "what if" setups that seems to have plagued this chase season. I certainly would have expected some monster supercells just basing off my earlier peeks at the boundaries, EHI, supercell composites, and Craven indices.

 

[Andrew Khan]

Wow, I am just continually confused about what is going on. Assuming the cap broke/weakened dramatically within the last 2 hours, why would convection, or precip not occur? GFS/NAM has been breaking out precip in this area for days (2), and now this? I am sitting at a rest stop near Ames, IA with Kurt Hulst, Fabian Guerra, and Skip Talbot....and we see a wierd belt of altocumulus, that is in wake with a 500 mb impulse...but nothing in signs of convection...and twilight, is nearing...

 

[Stan Rose]

Quite a few warnings/spotter reports out of NE CO today. Hope there's some folks out there
now who can post some reports: the tornado-warned cell near Yuma has some pretty impressive
low-angle velocity signatures!

 

[rdale]

Just had a plane flight into Peoria - still a notable inversion at 850mb as of 0150Z.

 

[MatthewCarman]

Stan Rose Wrote:

Quite a few warnings/spotter reports out of NE CO today. Hope there's some folks out there
now who can post some reports: the tornado-warned cell near Yuma has some pretty impressive
low-angle velocity signatures![/b]

Looks like the event was much farther west today. I was suprised that IA didnt not see a single severe storm today. I was waiting for a good show over IA today and look what happend. :angry: Still a chance tonight something could pop up but it appears that anything in the way of severe storms is low. SPC still has a 30% chance of hail and a 5% chance of tornadoes for Iowa.

Many Tornado reports farther west today and in a 2% chance area by the SPC. (Now a 5% chance) TOR warned storm in western kansas right now. There is reports of a tornado with this storm. Blakeman and Atwood are in the path of this tornado.

IN ADDITION TO THE TORNADO...THIS STORM IS CAPABLE OF PRODUCING
BASEBALL SIZE HAIL AND DESTRUCTIVE STRAIGHT LINE WINDS.

-MatthewCarman.