2/27/11 FCST: KS, OK, TX, MO, IL, AR, LA, MS

[jamesmseitz]

Looking at the models the upper air pattern is showing signs of possible eroding of the cap at about 4 PM. WTF is showing a bit of moisture starting at that time frame and with effective bulk shear showing signs of right turning storms around the 4 state corners (I.E. Tulsa to Joplin) tomorrow odds have shot up considerably. Still think the show will really ramp up towards the evening/nighttime with the signs of the Jet kicking in. Still I start in Joplin because of the Interstate so you could move quickly SW or NE accordingly to how the system plays out. Good luck to all going out.....

 

[Chad Cowan]

Surprised there hasn't been any mention of the cloud cover over the target area tomorrow. The NAM's cloud forecast on UCAR's site has been showing a lot of them which would mean initiation time is probably going to be dictated by whenever the shortwave decides to arrive. It's a testament to how high the surface moisture will be that we're even talking about tornadoes on a cloudy day (night) in February.

This 18z map shows a large area of low and high clouds over the target area. The NAM brings a moderate 700mb dry punch in around this time but the 0z map doesn't show much clearing, especially with the low clouds.

Regardless of how much sunlight is received, I think there will be tornadoes tomorrow but likely not until after sunset.

 

[Bill Tabor]

Looking at all the precip models so far NAM, GFS, WRF, HRRR - appears to me decent convection won't break out in OK until after 0z. NCEP 4km WRF-NMM does show convection in western TN at 19z and in northern OK near 1z west of Enid and by 2z / 3z is in central southern KS perhaps just east Medicine Lodge.

 

[RMacDonald]

Just looking at my latest output and still staying pretty consistent with a target area of Chanute-Pittsburg-Coffeyville, KS, to Joplin, MO to Miami, OK-Neosho, OK. Time frame for this is still looking around 02-05Z, but that keeps waffling back and forth, hoping to get a good time down in the morning. Any thoughts on potential for this area.

 

[Kelly Sugden]

I see SPC pushed back the slight towards ICT. Latest HRRR breaks out a cell in Kay county Oklahoma at 01Z. Thinking about heading out towards Arkansas City, KS.

 

[Trey Thee]

I am more than a little concerned with this cloud cover. Here in the Tulsa area we have a thick blanket of cloud cover in place. Visibilities are about 1 to 1.5 miles. But the air is VERY moist, my driveway, porch and deck look like its been raining for an hour.

If we can get some clearing and some destabilization we may be in business. But this cloud cover has me thinking there will be very few discreet cells this afternoon and primarily a line of svr that moves through the Tulsa area between 9pm and midnight.

edit: Just looked at SPC's page. They did indeed drop the MDT back fully into Arkansas now. They also moved the SLGT back to the west just a touch. This is somewhat disappointing as, that makes me believe they feel initiation may be limited as well

 

[Mike Smith]

Here is an interesting wrinkle: The 13Z RUC drops surface pressure 7mb at Blackwell in just 9 hours, a very fast pressure fall. Given the dynamics of this situation and the instability (see OUN 12Z sounding and the RUC forecast of 1,000 to 1,500j of CAPE in that area at late afternoon), I'm not sure that cloud cover will make that much difference. I'm pretty convinced that any thunderstorm that goes up in my "chaser tornado watch" will turn severe, provided it is along or just south of the warm front.

When I was researching "Warnings," I found that the great Woodward Tornado occurred on a day similar to today with lots of fog and overcast skies most of the day. Temperatures didn't reach their maxes along its path until 6pm or after. I am not saying we are going to get a Woodward-like tornado today. I'm simply pointing out that if the dynamics are strong enough, the overcast might not matter.

 

[Mike Johnston]

I am more than a little concerned with this cloud cover. Here in the Tulsa area we have a thick blanket of cloud cover in place. Visibilities are about 1 to 1.5 miles. But the air is VERY moist, my driveway, porch and deck look like its been raining for an hour.

If we can get some clearing and some destabilization we may be in business. But this cloud cover has me thinking there will be very few discreet cells this afternoon and primarily a line of svr that moves through the Tulsa area between 9pm and midnight.

edit: Just looked at SPC's page. They did indeed drop the MDT back fully into Arkansas now. They also moved the SLGT back to the west just a touch. This is somewhat disappointing as, that makes me believe they feel initiation may be limited as well

I definitely share your concern about cloud cover. But, I interpreted the westward shift in the SPC's risk areas almost completely the opposite; it sounds to me like some better possibilities for daylight initiation. To quote from their text: " LATEST MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE HAS TRENDED TOWARD A HIGHER PROBABILITY OF DIURNAL TSTM DEVELOPMENT THIS AFTERNOON INTO EVENING FROM THE VICINITY OF SURFACE TRIPLE POINT OVER S-CNTRL KS/N-CNTRL OK NEWD TOWARD MKC."

Latest RUC guidance shows CIN eroding across north central OK and south central into east central KS around 22z. Right now, Oklahoma mesonet shows a pretty sharp airmass boundary from roughly Hobart-Watonga-Blackwell, probably representing some combination of the incipient warm front and the usual dryline.

 

[Trey Thee]

Here is an interesting wrinkle: The 13Z RUC drops surface pressure 7mb at Blackwell in just 9 hours, a very fast pressure fall. Given the dynamics of this situation and the instability (see OUN 12Z sounding and the RUC forecast of 1,000 to 1,500j of CAPE in that area at late afternoon), I'm not sure that cloud cover will make that much difference. I'm pretty convinced that any thunderstorm that goes up in my "chaser tornado watch" will turn severe, provided it is along or just south of the warm front.

When I was researching "Warnings," I found that the great Woodward Tornado occurred on a day similar to today with lots of fog and overcast skies most of the day. Temperatures didn't reach their maxes along its path until 6pm or after. I am not saying we are going to get a Woodward-like tornado today. I'm simply pointing out that if the dynamics are strong enough, the overcast might not matter.

Wow, that is a massive pressure fall in that short period of time. I agree if the low deepens that quickly it won't matter much whether or not these clouds stick around. I'm curious to see what the 10:30 update will look like. This system looks to be pretty bad for central Ark.

 

[Trey Thee]

I definitely share your concern about cloud cover. But, I interpreted the westward shift in the SPC's risk areas almost completely the opposite; it sounds to me like some better possibilities for daylight initiation. To quote from their text: " LATEST MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE HAS TRENDED TOWARD A HIGHER PROBABILITY OF DIURNAL TSTM DEVELOPMENT THIS AFTERNOON INTO EVENING FROM THE VICINITY OF SURFACE TRIPLE POINT OVER S-CNTRL KS/N-CNTRL OK NEWD TOWARD MKC."

Latest RUC guidance shows CIN eroding across north central OK and south central into east central KS around 22z. Right now, Oklahoma mesonet shows a pretty sharp airmass boundary from roughly Hobart-Watonga-Blackwell, probably representing some combination of the incipient warm front and the usual dryline.

I think I wasn't clear...I believe there will likely be convection west of here on the I35 corridor, but I think it'll be two or so storms that go up. It will be fairly limited in coverage but I think there will be one or two storms go up between OKC and Wichita. But given the setup I'm not sure we'll see more than that. That's what I meant by limited initiation...I didn't mean there would be no initiation. Sorry for the confusion.

 

[Mike Smith]

Under "Murphy's Law of Meteorology" the probability of tornadoes goes up in proportion to the number of radars that are out of service. Both ICT and Vance's WSR-88D's are currently down. So, if you need to look at a radar, here is the Wichita TDWR: http://www.wunderground.com/radar/radblast.asp?ID=ICH Keep in mind that it is a 5cm radar so intensities might be less and attenuation is more of an issue. The good news is that the velocities are very high quality.

I forgot to add to my post above that if I were to try to position myself for a "chasable" tornado, I'd still position myself in Blackwell.

 

[Michael O'Keeffe]

I am liking the area in NW OK and far SC Kansas and think if storms can go we will see supercells and maybe a few tornadoes but a more enticing area after looking at the HRRR and RUC is NE AR/W TN. Skies in this area are clearing a bit better than the OK/KS target (though its not much better) and both the HRRR and RUC have a couple nice cells firing near Jonesboro, AR and tracking eastward in W Tennessee after 2pm. I'm guessing there is some sort of pre frontal wave ahead of the main upper level trough to fire off these storms and the cap looks non existent in that area by mid afternoon. CAPE isn't too bad in that area either with widespread 1000-2000j/kg over much of E AR/SE MO/W TN. If the RUC and HRRR are right about this then it looks like the SPC's moderate risk placement was a smart one. So while not in a very chaseable area this seems like more of a sure bet with daytime storms a very good possibility.

 

[Jeff Piotrowski]

Per the new 15Z RUC looks like the WF from SE/KS-NW/OK tornado threat is increasing by 21Z also of note is the surge of high cape 2500 across Western OKLA. headed toward Woodward ahead of the DL.

 

[cdcollura]

Good day all,

In addition to the enhanced tornado-threats in the forests of Arkansas and such, anyone notice on the RUC an area of potential hanging back near Enid, OK at around the 9-10z time frame?

The 9z RUC is showing a "triple point" type feature (with a nose of high theta-e and dewpoints wrapping to the NW around the developing colorado low to the west). Precipitation is also broken out as a "tail-end" type structure in this area. By 12z, it appears the cold front will over-take the dryline so the window of opportunity before dark is about 3 hours or so. Also, CAPE and helicity is high in this area, with a little "hole" in the CIN being developed by 9z as well.

In the "main" areas farther east, a second lobe of the intensifying low should develop by 12z, with most of the strong tornado potential being from Arkansas and eastward towards Memphis, TN with the warm front / convergence (very BAD chase terrain after dark). The best area in the stronger eastern setup in the forests should be towards NE Arkansas and NE of there, with a convergence area juxtaposition to the warm front. Any supercells there should be poor-visibility HP storms, and late afternoon / after dark presenting poor chase prospects, with motions 50-60 MPH (race chasing). The danger here is for the people who live there.

The second targets farther west from N-Central OK before the front catches the dryline should be an earlier and more "chaseable" setup if the RUC verifies. A region of -25 C (or colder) 500 Mb temps also appears to be over spreading the chase areas, especially the western one over OK by the 9-12z time frame, so any cap should be eroded by this.

I'm not chasing this one, but I wish anyone who goes out to be safe, good luck, and have fun!

 

[Mike Smith]

Here is an interesting wrinkle from the 15Z RUC. As previously noted, there is high (for February) CAPE and high helicity over northern OK and far southern KS. The PVA is a little faster than thought last night and look at this:

One hundred fifty knot winds right over the threat area (at 21Z per forecast RUC) with difluent flow! From 15Z to 21Z, the pressure drops 6mb at Blackwell per the RUC.

Given that the CAPE around WWD becomes uncapped, and that helicities are about 250, this area is starting to look quite potent.