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Severe Weather Thread: 03/03/2011 - 03/06/2011


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I figure with this next thread we just keep it on a weekly scale unless we really get a event going. The GFS is looking favorable for severe weather in North Texas/Southern Oklahoma Friday Evening as a low pressure develops in West Texas, allowing an instability axis to develop around the Vernon/Wichita Falls vicinity. While the low level flow is weak, it is present. We're watching this for our next possible chase, and I know several other chasers are watching it as well.

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I figure with this next thread we just keep it on a weekly scale unless we really get a event going. The GFS is looking favorable for severe weather in North Texas/Southern Oklahoma Friday Evening as a low pressure develops in West Texas, allowing an instability axis to develop around the Vernon/Wichita Falls vicinity. While the low level flow is weak, it is present. We're watching this for our next possible chase, and I know several other chasers are watching it as well.

SPC watching it but not biting yet...

ZCZC SPCSWOD48 ALL

ACUS48 KWNS 010842

SPC AC 010842

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0242 AM CST TUE MAR 01 2011

VALID 041200Z - 091200Z

...DISCUSSION...

PRIMARY ATTENTION IN THE MEDIUM RANGE WILL REVOLVE AROUND A

MID-LEVEL TROUGH THAT WILL TRANSLATE FROM THE ROCKIES INTO THE

PLAINS AND MID-MS VALLEY FRI-SAT AND THE ERN STATES BY SUNDAY.

THERE REMAINS A CONSIDERABLE AMOUNT OF SPREAD IN 00Z MREF ENSEMBLE

MEMBERS...00Z ECMWF AND 00Z GFS. ECMWF CONTINUES TO OFFER A MUCH

STRONGER AND SLOWER SOLUTION WHICH COULD GIVE RISE TO SOME SEVERE

WEATHER ACROSS THE MID-SOUTH/LOWER MS VALLEY AND SRN STATES SATURDAY

AND SUNDAY. GIVEN THE CONTINUED VARIANCE IN MODEL

SOLUTIONS...PREDICTABILITY REMAINS TOO LOW TO CONFIDENTLY PLACE A

SEVERE WEATHER OUTLOOK AT THIS TIME.

BEYOND THE WEEKEND...THERE IS REASONABLE AGREEMENT IN MEDIUM RANGE

MODELS IN DEPICTING A BROADER MID-LEVEL TROUGH MIGRATING ACROSS THE

CNTRL/SRN ROCKIES INTO THE CNTRL/SRN PLAINS BY NEXT TUESDAY /DAY 8/.

MOISTURE RETURN AHEAD OF THIS SYSTEM WILL BE IN QUESTION AND WILL

HINGE HEAVILY ON HOW STRONG THE AFOREMENTIONED LEADING SYSTEM

BECOMES AND HOW FAR S THE ASSOCIATED COLD FRONT PENETRATES INTO THE

GULF OF MEXICO.

..RACY.. 03/01/2011

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Maybe some extreme North Texas/Oklahoma action as early as Friday afternoon/evening per Euro. Euro CAPE reaches 500 J/Kg around the Red River then.

Call me selfish, better videos on YouTube daylight and in extreme North Texas and Oklahoma. Reduced risk to life as well.

Normally I hotlink ECMWF site images, but they are squirelly today...

post-138-0-96933300-1298985606.gif

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Just reviewed the wind profiles for 3/5 - very impressive and down right nasty looking. Nice upper level support and shear, CAPE is between 500 and 1500. EHI values running about 3.50 over west OK. LI -7. Helicity is stronger along the warm front in KS, there is still plenty over western OK.

The problem is - is there enough moisture to get surface based storms? Dewpoints at THIS time do not look impressive. The LLJ if you follow it is directly out of southern TX, not the GOM. More of the deeper moisture is over Eastern OK and AR. So storms may not become surface based until they pass OKC to near TUL.

Probably will see more smaller tornado outbreak along the warm front again, like this more recent event. Looks like to me a small outbreak may occur between TOP/WIT/TUL/SGF along the warm front. Bigger event may happen the following day in AR/KY/TN/IL/IN.

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I'm pretty much with Tony here. In terms of notable tornado potential in the warm sector, I think it would require boundary layer dew points 4-6 F higher than current progs. That's an awfully large model error in the direction of underestimating moisture, especially for early March. Of course, the starved chaser in me is still trying to justify how we can get magnificently-sculpted LP supercells out of this, despite 1500-2000 m LCL's and the associated cold pool issues (given initiation).

I suppose if you take the 01/12z NAM and reduce surface temperatures from 75-78 F closer to 70-72 F, you'd lower LCL's enough to possibly see something akin to March 2, 2008. That day produced one tornadic supercell at the triple point in W OK in an environment characterized by similar H5 temperatures, low-mid 50s sfc Td's, and ~1000 J/kg SBCAPE.

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I agree that Friday will most likely be more a structure photograph day then anything related to do with tornadoes, but I'm a storm chaser so I'm looking forward to the opportunity. I've written up a blog post discussing Friday's chase plans and possible outcomes.

Interested parties can read it at http://www.texasstormchasers.com/2011/03/01/back-to-oklahoma-for-friday/

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Meh. Maybe next week.

I think both systems have potential....there is a strong LLJ in both systems with on avg a 150-170 deg trajectory which would bring gulf moisture north to at least the Ark latex region....and the second system is a much stronger system (granted we are way out there a bit in the forecast hours) but from a pattern recognition standpoint it certainly bears watching. The GFS didn't forecast much instability with the last system due to it's NWP parametrization which initializes from a climatological average (it showed 500-750 and LI's of -2 and mesoanalysis verified 3000 and -8). At the very least with the dynamics one would have to be concerned with a severe NCFRB. I believe once it gets into the range of the NAM if the progs hold on the GFS there could be a severe threat up to the northern Missouri central Illinois with either system, but more so the Tuesday system.

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Setup didn't look that good to me but I didn't look at it for long. Strong winds aloft though.

LMK seemed pretty stoked about it too, even mentioned similar set up from the last storm. I think maybe they were talking more QPF wise than anything but they did mention squall line.

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Norman has their eye on next week too.

EARLY NEXT WEEK... ANOTHER STORM SYSTEM IS FORECAST TO WIND UP

OVER THE SOUTHERN PLAINS. WINDY AND WARM CONDITIONS ARE EXPECTED

AHEAD OF THE SYSTEM... WHILE WINDY AND COOLER WEATHER WILL FOLLOW

IT. TIMING AND POSITION OF THE MAIN FEATURES WILL BE CRITICAL IN

DETERMINING WHAT KIND OF WEATHER WILL AFFECT OUR FORECAST AREA. IF

THE DRY SLOT COVERS OKLAHOMA... WE WILL SEE A WARM AND DRY DAY

WITH HIGH FIRE DANGER. THIS IS THE SCENARIO ENVISIONED WITH THIS

NEW FORECAST. HOWEVER... IF THE STORM DEVELOPS A LITTLE FARTHER

WEST... OR EARLIER... TUESDAY WILL BE A MUCH MORE INTERESTING DAY

IN CENTRAL OKLAHOMA... IN TERMS OF CONVECTIVE DEVELOPMENT THAT IS.

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One thing I would point out is that the models all agree that the mid/upper level temps will be abnormally cold with this system, so it will not take as robust of moisture in the warm sector to generate decent instability. Of course, what they don't agree on is the structure of the trough and frontal system, so we'll see how much of a threat actually evolves.

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Gotta love low-amplitude shortwaves and the model timing errors they bring. New 02/00z NAM says any threat for Friday is focused on W AR, about 250 mi. displaced from this morning's run. Still doesn't look particularly significant in terms of tornado potential, and the low-level wind fields are substantially weaker. Unfortunately, even if it produced some supercells, they'd be of little use to chasers given that location.

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Gotta love low-amplitude shortwaves and the model timing errors they bring. New 02/00z NAM says any threat for Friday is focused on W AR, about 250 mi. displaced from this morning's run. Still doesn't look particularly significant in terms of tornado potential, and the low-level wind fields are substantially weaker. Unfortunately, even if it produced some supercells, they'd be of little use to chasers given that location.

ya its really amazing how different this run is compared to the 12z NAM, that run had the northern stream wave up near MT attempting and phasing some with the southern stream s/w coming out. The 18z and the new run are having none of that and therefore ending up much weaker.

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