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April 12th/13th and 15-16th Severe Weather Thread


andyhb

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To be honest, i'd rather play the WF than the dry line. Hodographs are disgusting up that way, and probably everybody and their mother will be on the dryline.

That's exactly where I'd go. Plus, you may get a couple more hours of storms in daylight than on the dryline...if the models play out close to what's being predicted.

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Yeah I agree, I was just looking for an excuse not to head that way. Seems like I35 has all the attention with this event, but eastern NE seems like a better spot to be. The low level/deep layer shear is so strong with sufficient CAPE it seems storm mode will stay mostly discrete.

It will have its own pitfalls for chasing though, namely the Missouri. I've done that dance before.

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Yeah I agree, I was just looking for an excuse not to head that way. Seems like I35 has all the attention with this event, but eastern NE seems like a better spot to be. The low level/deep layer shear is so strong with sufficient CAPE it seems storm mode will stay mostly discrete.

This is what I said in my report to clients/management today (in layman's terms). Everyone seems way too focused on KS/OK. I think anywhere from Omaha-Lincoln to KC & SW Iowa are good spots, depending on where the warm front lies. Triple point & boundaries FTW.

This same situation played out on March 2. Everyone was so focused on central KY & central TN High Risk area (early at least, before the High was expanded north). I was convinced southern IN was the place to be, mostly because models were persistent on putting a Theta E boundary there.

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12z RGEM and 12z GFS are really ramping up the strength of the upper low. RGEM has a tendency to be a bit over amped sometimes, but it goes 985 and cranks up the low in western NE with a neutral tilt low. Big changes have a tendency to come at this stage as the upper low begins to cross over the pacific coast...any increase in the low level mass fields just ramps things up all that much more.

This pretty much ends the discussion regarding doubts about convective initiation anywhere north of the Red River.

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What is the thinking for the probs they will issue with watches tomorrow? Do you guys think it will be as crazy as the PDS watch on April 27th with everything in the 90-95% range?

Way too early to think about that stuff, because it is going to depend on how things evolve early tomorrow. My early guess for tornado probabilities tomorrow would be 45% (and hatched of course) to leave room for higher probabilities once the highest risk areas show their hand so to speak.

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This is quite reasonable.

This is what I said in my report to clients/management today (in layman's terms). Everyone seems way too focused on KS/OK. I think anywhere from Omaha-Lincoln to KC & SW Iowa are good spots, depending on where the warm front lies. Triple point & boundaries FTW.

This same situation played out on March 2. Everyone was so focused on central KY & central TN High Risk area (early at least, before the High was expanded north). I was convinced southern IN was the place to be, mostly because models were persistent on putting a Theta E boundary there.

I favor a two round episode. The second round is the KS/OK stuff, but they could have am action too. First round will lay OFB down there. However in this robust of a set-up, first round may deliver tornadoes in NE/IA early. Regardless of whether NE/IA repeats, the morning would still have verified TOR.

Models seem to have shifted WF north. Even if that is wrong, LNK-OMA-MCI should watch out for round 1. Flight into KC? Might not have to relocate far.

EDIT: SPC added High north as I typed. I feel original now, lol. IMO don't count out CNK-MHK-TOP. Good luck and chase safe!

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This pretty much ends the discussion regarding doubts about convective initiation anywhere north of the Red River.

This is such a tough one. Even the hi-res WRF runs I've looked at this morning seem very hesitant about anything more than isolated cells south of ICT (or even I-70), so it's not just the NAM. SPC and NWS OUN seem to share concerns about coverage in that area, as well. A major outbreak all the way to the Red River remains quite possible, but this one doesn't seem as straightforward as 24 May 2011 or 10 May 2010 (those did have capping concerns, too, but IIRC it wasn't quite like this, as they were more strongly-forced).

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Here is a SPC outlook as it related to OK/KS

...CNTRL KS...WRN AND CNTRL OK...NWRN TX...

SUBSTANTIAL UNCERTAINLY EXISTS IN REGARD TO STORM COVERAGE ALONG THE

DRYLINE DURING THE DAY FROM KS INTO OK AND NW TX. HOWEVER...HIGH END

SEVERE POTENTIAL EXISTS AND WILL MAINTAIN CATEGORICAL HIGH.

LOW CLOUDS AND SCATTERED SHOWERS ARE EXPECTED EARLY ON SAT...WITH

ONLY SLIGHT CAPPING IN PLACE EARLY. BREAKS IN THE CLOUDS AND HEATING

SHOULD QUICKLY ERODE MOST INHIBITION BY AFTERNOON...WHEN WITH

MODERATE INSTABILITY DEVELOPING WITH MUCAPE GENERALLY 2000-2500

J/KG.

STRONG HEATING AND STEEPENING OF LOW LEVEL LAPSE RATES WILL OCCUR

ALONG AND W OF THE DRYLINE. HOWEVER...CONVERGENCE WILL BE RELATIVELY

WEAK...WHICH MAY ACTUALLY HELP KEEP STORMS DISCRETE. FAVORABLY

ORIENTED DEEP LAYER SHEAR ALONG THE DRYLINE...AS WELL AS VEERING AND

INCREASING WINDS WITH HEIGHT WILL STRONGLY FAVOR SUPERCELLS.

THERMODYNAMIC PROFILES SHOULD BE SUFFICIENT FOR VERY LARGE

HAIL...AND LOW LEVEL SHEAR WILL FAVOR TORNADOES AS WELL. LAPSE RATES

ALOFT ARE MARGINAL FOR TYPICAL PLAINS VIOLENT TORNADO DAYS...BUT

SHEAR PROFILES WOULD CERTAINLY FAVOR A FEW STRONG TORNADOES.

CURRENT THINKING IS FOR ISOLATED TORNADIC SUPERCELLS WITH VERY LARGE

HAIL TO FORM ALONG THE DRYLINE...AND TO PROCEED NEWD ACROSS THE HIGH

RISK AREA LATE AFTERNOON INTO THE EVENING. THEN...THE PACIFIC FRONT

WILL MOVE IN FROM THE W...LIKELY RESULTING IN A SQUALL LINE CAPABLE

OF DAMAGING WINDS WITH EMBEDDED AREAS OF ROTATION CAPABLE OF DAMAGE.

FARTHER S INTO TX...DAYTIME DRYLINE ACTIVITY IS LESS LIKELY...WITH

THE MAIN SEVERE THREAT COMING FROM THE OVERNIGHT SQUALL LINE WITH

DAMAGING WINDS AND PERHAPS TORNADOES WITH SUPERCELLS EMBEDDED WITHIN

THE LINE.

At this point this isn't screaming bust as much as cells may be more isolated.

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This is such a tough one. Even the hi-res WRF runs I've looked at this morning seem very hesitant about anything more than isolated cells south of ICT (or even I-70), so it's not just the NAM. SPC and NWS OUN seem to share concerns about coverage in that area, as well. A major outbreak all the way to the Red River remains quite possible, but this one doesn't seem as straightforward as 24 May 2011 or 10 May 2010 (those did have capping concerns, too, but IIRC it wasn't quite like this, as they were more strongly-forced).

I certainly think the storm coverage is going to be rather isolated south of the KS/OK border, that I totally agree on. Whether that actually does much to taper the magnitude of the event down there is another matter, as discussed in the SPC outlook. For example, 5/24/11 was an event that was limited IMO because cells initiated too early and there were too many of them close together. The relationship between how scattered the cells are vs. how severe the outbreak can be unclear sometimes.

I will say though that the confidence in the KS/NE part of the outbreak is higher for all of the reasons that have been discussed.

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I certainly think the storm coverage is going to be rather isolated south of the KS/OK border, that I totally agree on. Whether that actually does much to taper the magnitude of the event down there is another matter, as discussed in the SPC outlook. For example, 5/24/11 was an event that was limited IMO because cells initiated too early and there were too many of them close together. The relationship between how scattered the cells are vs. how severe the outbreak can be unclear sometimes.

Not to mention that it only takes 1 strong tornado moving through a heavily populated area to 'make the day'.

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This is such a tough one. Even the hi-res WRF runs I've looked at this morning seem very hesitant about anything more than isolated cells south of ICT (or even I-70), so it's not just the NAM. SPC and NWS OUN seem to share concerns about coverage in that area, as well. A major outbreak all the way to the Red River remains quite possible, but this one doesn't seem as straightforward as 24 May 2011 or 10 May 2010 (those did have capping concerns, too, but IIRC it wasn't quite like this, as they were more strongly-forced).

I certainly think the storm coverage is going to be rather isolated south of the KS/OK border, that I totally agree on. Whether that actually does much to taper the magnitude of the event down there is another matter, as discussed in the SPC outlook. For example, 5/24/11 was an event that was limited IMO because cells initiated too early and there were too many of them close together. The relationship between how scattered the cells are vs. how severe the outbreak can be unclear sometimes.

I will say though that the confidence in the KS/NE part of the outbreak is higher for all of the reasons that have been discussed.

This is going to sound like an obvious statement, but it really comes down to trough ejection/configuration. There really is a split camp here between the GFS/RGEM and the ECMWF/NAM (12z ECMWF looks sheared w.r.t the upper low similar to the NAM). UKMET is down the middle. I think it would take a UKMET/GFS/RGEM solution to force strong enough low level convergence along the dryline to overcome cap concerns...which is clear in the disparate model solutions regarding initiation. Unfortunately these weakly positive tilt waves intersecting an already meridional warm sector are extremely challenging to forecast in terms of deepening and cyclogenesis. Minute differences w.r.t. the angle of intersection of the upper PV/low level theta anomaly can have rather massive differences.

Any solution, however, seems to favor NE as you mentioned. I35 the bigger question.

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