05/07/05 FCST:Central Plains

[Adam Atkins]

Tomorrow

I couldn't be happier with the 6Z day one SPC outlook. Why? It means less chasers will be out in the I40 W domain. I have a feeling most people use the SPC's outlook as their primary chase tool, which is intelligent and useful, but in this case, it seems their preoccupied with other things. They fail to mention anything about the veered mid/upper level flow near the base of the shortwave trough.

Unfortunately I don't see any large scale subsidence to clear out the deep moisture ahead of the dryline, and as Snyder said, it could be a very skinny CAPE axis, which from my experience, SUCKS for chasing. I'd equate it to a rollercoaster ride, up and down (storms).

I'm banking on the possibility of isolated convection due to upper level convergence in the right exit region of the jet. The more isolated the storms, the better the chasing, however, as previous research has shown, outflow boundaries locally increase the helicity and CAPE, leading to the formation of tornadoes.

Tornado potential definitely increases through the late afternoon, early evening when moisture increases and mid-level flow becomes more veered.

Sunday looks like a heavyweight match between storms, so I'm chasing tomorrow.

 

[Mike Peregrine]

You might be surprised how many will still opt for the southern options tomorrow, even with the 5% tor prob up north. Questionable shear aloft and inconsistent handling by the models of this 'event' makes it possible that this day is just a bust waiting to happen ... by the same token, this could end up becoming a sleeper day in the making ... complex forecasts like this one are not easy for me to figure out. Interested in seeing how RUC chooses to handle tomorrow as the low becomes better defined. If I had the time to make the drive, I would likely target extreme north-central Neb into south-central S. Dak, as initiation appears probable to the north first and then working its way back to the south. Wind profiles remain favorable for supes down to Concordia, KS, where NAM at 21z shows L.I. of -5.1 ... CAPE at 2000 ... SWEAT of 405 ... Supercell pct. at 78 ... and very good low level veering. Storm speed again looks manageable tomorrow, though not as frozen in time as the storms were today. The question will be timing further to the south in the SPC 5% zone ... hoping that if this does get going it will kick off early enough to see something. My current target tentatively stands from York to Columbus, Nebraska. We'll see how it looks in the a.m. (when hopefully current convective clutter will begin clearing to the west and a few outflow boundaries begin offering some hope).

 

[Jeff Wear]

Think we'll at least see some picturesque supercells across the TX panhandle tomorrow. The narrow instability axis isn't anything I'm too worried about - I can recall a number of decent chase days where gunge broke out across OK during the morning while storms fired in a relatively narrow area of instability in between the dryline and the gunge - 5/23/2002 and 4/15/2003 are two I can think of. And the area of instability might not be as narrow as feared depending on how far east the dryline gets.

 

[Amos Magliocco]

I agree about the potential in the Texas panhandle, with moisture and weak LLJ as the main limiting factors for long lived supercells. I'd like to see the clouds burn off sooner rather than later, too, though this seems to be underway. I'm headed for Shamrock to check data, then likely south toward CDS area and progged dryline bulge.

 

[Jeff Snyder]

LOL SO my grungefest concern BUSTED! LOL but at least this time it's a good bust! Vis sat currently shows scattered-broken high-level cirrus clouds the area, but not much in the way of any sort of stato or srato-cu deck.

On the other hand, I notice that the 60 degree isodrosotherm is still down along a line from San Angelo to Waco, or 250 miles south of Shamrock. So, advection alone will probably not get it into the area. Cmon pooling and evapotrans!

Interesting that AMA has southwesterly winds. Td there is still 58, but if that marks the dry 'wind shift', then expect the dry air to mix down rather quickly and cause the 'dryline' to shift just east of AMA. Haven't really had time to check out the models from this morning (well, mainly the RUC since the NAM isn't out yet). Plan is still to head to Shamrock and readjust from there. No cell data today since phone is at Motorola repain in Fort Worth --> Ugh.

 

[Bill Schintler]

Chase target for today, May 7

Chase target:
40 mi. E of Valentine, NE

Timing:
Storm initiation near Valentine around 4 PM CDT, with storms tracking to the northeast at 20 mph.

Storm type:
Fairly high-based supercell storms with bases around 1500m AGL, some of which will produce large hail.

Discussion:
As expected, a large MCS developed and tracked across much of IA and MN, resulting in a number of outflow boundaries that will play a significant role in renewed afternoon convection. In IA, one such boundary appeared to be located along a DBQ-SLB-YKN line at 13Z; while a second boundary, perhaps the synoptic WF, was located along an AWG to CIN line. In NE and SD, the primary synoptic boundary was located from MHE to PIR to the low-pressure center near HEI, while a boundary was noted along a VTN to ANW line. I am focusing on this mesoscale boundary as a candidate target location, with a region of locally backed low-level surface flow along and to the NE of this feature.

Later today, a strong vort max will approach WRN NE while 0-6km shear reaches 50kts along with MLCAPE’s around 1000J/kG.

- Bill

 

[Shane Adams]

Latest ETA paints an obvious bullseye over the Shamrock, TX area. UVV spike very nice and indicitive of isolated activity, along with a CAPE max in excess of 2000j/kg. What I really like about this latest run is the stronger h5 winds, now showing in excess of 45kts over this area. This should help keep any discrete storm sustained for quite some time. LL winds aren't particularly strong, but the slightly backed h85 flow is juxtoposed nicely with the sw h7 winds. Speed shear from h7-h5 is nice as well, so any storm tha gets going should have a rail to ride on. I'm all excited about the buldge in the windshift line in the central TX pan, which will no doubt be the focus point for activity in this area later today. Also picking up a hint at a possible mesolow forming in SE New Mexico, just WSW of the windshift axis center. Surface temps are progged in the 80s while dews will be in the 60s. Add in the higher elevation and you have a decent chance for a tornado or two from any isolated sup that can form. Target as of now is Shamrock.