04/24/06 FCST: KS/OK/TX

I have no idea why SPC would place the mod. risk that far northeast. I am sure it will be corrected in the next outlook.
We already have dewpoints in the mid 60's across the target area and as Jeff mentioned, we may actually gain a few degrees with mixing. I noticed that last night when I was checking forecast soundings, but I didn't think too much of it. If the low and mid level flow is as strong as the NAM was forecasting, we should be in good shape today. A lot more will become clear as the day progresses, but so far so good.
 
I have no idea why SPC would place the mod. risk that far northeast. I am sure it will be corrected in the next outlook.
We already have dewpoints in the mid 60's across the target area and as Jeff mentioned, we may actually gain a few degrees with mixing. I noticed that last night when I was checking forecast soundings, but I didn't think too much of it. If the low and mid level flow is as strong as the NAM was forecasting, we should be in good shape today. A lot more will become clear as the day progresses, but so far so good.
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Mike, I think they are following the oldest Nam run: after looking yesterday 12Z Nam the most favourite place for chasing was just the zone south-est of Wichita, the zone of the 10% of tornadoes; now the low pressure is forecasted to be in a more south-west oriented position so I think that in the next run SPC will adjust the map.
Guys, I love Harper-Pratt-Medicine Lodge county....Anyone knows why? :rolleyes:
 
Mike, I think they are following the oldest Nam run: after looking yesterday 12Z Nam the most favourite place for chasing was just the zone south-est of Wichita, the zone of the 10% of tornadoes; now the low pressure is forecasted to be in a more south-west oriented position so I think that in the next run SPC will adjust the map.
Guys, I love Harper-Pratt-Medicine Lodge county....Anyone knows why? :rolleyes:
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Well after some extensive analysis and discussion, I will get to make my first chase of the season thanks to a combination of no class and work. Derek Williams and I will be setting up initially in Enid, OK and play the T.P. from there as it moves ENE across North Central OK. The flow at 250mb does seem to be a bit perplexing but with the other dynamics in place, I am less inclined to stress out about it. As we speak, the Mesonet shows dewpoints already in the mid 60s with a gradual rising trend from south to north. Looking out my window in East Norman I see some elevated TCU putting out quite a bit of lightning and precip which makes me feel even better about the day (any moisture at this point makes me happy...omens).

On a side note, is there anyone out there that would want to nowcast today?
 
I don't mean to get off topic, but I wanted to respond to Andrea. The 00Z NAM had the surface low in NW to west central Oklahoma. I am also pretty sure that even the 12Z from yesterday had the low in the same place. I don't remember seeing any runs within the last 36 hours that had the triple point close to Wichita. The same SPC forecaster was a little off on yesterday's first outlook as well. The moderate risk is in the right place now though so it's water under the bridge.
 
I don't mean to get off topic, but I wanted to respond to Andrea. The 00Z NAM had the surface low in NW to west central Oklahoma. I am also pretty sure that even the 12Z from yesterday had the low in the same place. I don't remember seeing any runs within the last 36 hours that had the triple point close to Wichita. The same SPC forecaster was a little off on yesterday's first outlook as well. The moderate risk is in the right place now though so it's water under the bridge.
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Mike, I remember yesterday 12Z Eta and low pressure was oriented in a more North-Eastern position than today: infact making a target I did agree with the moderate of SPC, ie it seemed that South East of wichita to the border with OK was an hot zone.
Now I agree another time with the newest position of the moderate.
 
The Enid area looks pretty good for a starting point... There are numerous 68F dewpoint readings in northern and central Texas at this time, with a few 70F dewpoints in central TX. With 50-60kts at 850-900mb overnight, plenty of juice was advected northward just above the stable near-surface layer. The 12z Lamont sounding showed 3700 muCAPE (for a parcel near 830mb), which is very impressive. I'm not sure if we'll see widespread 70-73F tds in northcentral OK like the 12z RUC is showing, but 66-68F seems reasonable given evapotranspiration. I also don't know as if I believe the forecast locations of the cold front this afternoon. Winds the OK Panhandle are NNW at 30-40mph right now, with strong (3mb/3hr) pressure rises. Pressures shoiuld fall east of the cold front this afternoon, so I really can't believe that the cold front will only move 2 counties to the southeast this mid-afternoon. This will just be another complication by afternoon, since I'm inclined to think 'squall line' if the cold front moves any faster. As it stands now, 0-4km shear vectors may be due east or even ESE by afternoon, which will mean that there may be a significant component of the deeplayer shear that is normal / perpendicular to the front.

EDIT: The 12z is indicating that the triple-point will set up in west-central/southwestern OK, with a dryline bulge running from near Shamrock TX to Frederick OK to just west of SPS. It does look like the low forecase is shifting southwest in time (12z NAM shows it just south of Vernon by 0z).
 
model trend seems to be pointing more toward the surface low setting up even further southwest - perhaps even south of the Red River. Solutions differ significantly in how the trough will set up north of there. In the 12Z RUC, an elongated trough extends NNE by 0z, which results in veered surface winds ahead of the cold front until you get all the way back into extreme SE KS, where the RUC and SREF both suggest a potential play as a weak shortwave skirts the ridge and leds to a weak mesolow tracking along to north of the OK-KS border, intersecting with the convective outflow boundary from ongoing storms this morning. Morning NAM looks far too agressive in developing precip in eastern OK this morning, so I doubt that model's solution of backed winds extending nearly down to the low. Some sort of compromise seems reasonable until the atmosphere settles down a bit - which isn't too far off from what the current SPC outlook seems to highlight, but wouldn't be surprised to see the tornado threat elongated eastward a bit on the northern end, with large hail stretched a bit further southwest.

Glen
 
Very complex setup this morning. The models, and this human, are having a tough time. The cold front appears to be stronger/faster than the 12Z NAM/eta suggests...and should extend from Plainview to Altus to Medicine Lodge by late afternoon. Meanwhile the outflow boundary in southern Kansas is getting shoved southward faster on its eastern end, and by later today should extend ESE to WNW from Tulsa to Medicine Lodge. Oh, and the dryilne will also be out there early but occluded by the front somewhere in the Childress vicinity.

So there could be low pressure centers at Childress, Medicine Lodge, or both. I suspect as the front advances, the northern target storms will be undercut, and the deep shear vector would be nearly parallel to the boundary, so I'm leaning toward the southwest at the moment. The best scenario might be the southern low being as strong as the NAM/eta suggests, which would hold the boundary at bay during the afternoon in western Oklahoma. Probably a second target along the old OFB well east of the advancing front, perhaps near I-35 in north central Oklahoma.
 
RUC breaks out supercells along the dryline by 21Z...more discrete cells the father south you get into TX. Also, RUC has CAPE values up to 4500 j/kg. Should the surface flow stay backed in Cent. Okla. I think that west on I 40 would be a good place to start.
 
Watching the obs for a bit - pretty well defined outflow boundary surged south across SC KS, and is now settling in on the western extent just south of the OK-KS border - with weakening pressure gradient to the north, and strengthening pressure gradient further east which should help the boundary sag further south into northeast OK. Trend in convection in OK seems to be toward weakening, except for those storms settled into the warm frontal trough - nearly aligned with the mean upper flow so slow moving. western extent seems to be weakening now though. Also noting the surface low, now over western OK, is indeed sagging southward - with veering winds to its east as advertised by this morning's RUC (which has the warm front much too far south though in the initialization). I'd expect the boundary to hold out around the northern tier of OK counties and provide a favorable environment by afternoon.

Glen
 
Okay, after looking at the 12z data, I have made the decision to change my setup location to Clinton/Weatherford due to the new positioning of the low further south. This was due in part primarily to the wind direction progged by the NAM to already be north/northwesterly by 0z in Enid (my original target). I'd rather not run the risk of my storms getting undercut by the cold front so I think we'll play it further south and then bust north if we have to as opposed to going north and then having to come all the way back down again.
 
New outlook is out from SPC, up to a 15% tornado area and a 60% hatched hail...

Looking at forecast soundings for Oklahoma shows CAPE values around 3000 at 21z as well as high values for other severe indicies...

Looking at the Mesonet data, there's an area of 67°F dewpoints advecting northward into Central OK...reaching as far north as the Spencer site as of 11:25.
 
Chase target:
Freedom, OK (20 miles northeast of Woodward).

Timing:
Storm initiation 4 PM CDT.

Comments:
Supercell storms capable of very large hail and tornadoes from the time of storm initiation through 8 PM, after which storms will evolve into a large complex. Storm motion will initially be east or southeastward at 15 MPH early in evolution.

Discussion:
An OFB analyzed along an AVK/WDG/SWO line is moving S at 30 mph, and it will be at the triple point of this feature and a DL that will move to the east that will be for focus for renewed convection later this afternoon. A very unstable airmass will be in place, with SBCAPE’s approaching 5000J/kG as surface dewpoints exceed 70F. Backed SFC flow N of the DL will result in impressive hodograph curves, while deep layer shear will be in the 50 knt range with the approach of the H5 trough. With strong insolation, it is expected that the CIN will rapidly erode between 19Z and 21Z.

- bill
 
Seems that the consensus with much of the group is along or near the Northwest Passage... I can't see any reason to disagree... so long as no more elevated convection develops in north-central OK. The OFB needs to become quasi-stationary... if the winds north of the OFB in north central OK become more 110-120º, I think that area will be in business for tornadoes. Otherwise, it seems questionable.

For those interested, this falls within our short-fuse composite domain that we run at NWS-DDC. It's at http://weather.gov/ddc/shortfuse/shortfuse.php. We are currently experimenting with a short-fuse composite threat area empirical formula that combines the components of the SFC. This graphic is at http://www.crh.noaa.gov/images/ddc/short/SFC3test_latest.png

Good luck all!

Mike U
 
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