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Significant Severe Events: June 14th-19th


andyhb

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I find it funny how people keep resorting to the NAM--including myself-- despite how absolutely awful it's been this year with almost everything, even this close to the event, seems to overexadgerate a lot.

 

It's the only 00z model up for discussion right now...

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It's the only 00z model up for discussion right now...

still doesn't take away from the fact that it's one of the first models always brought up... And seemingly always because of it's nuts parameters it always seems to show. And it's nearly always wrong in at least one major way, if not more.
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still doesn't take away from the fact that it's one of the first models always brought up... And seemingly always because of it's nuts parameters it always seems to show. And it's nearly always wrong in at least one major way, if not more.

 

Which model are you referring to? The 12KM NAM or the 4KM NAM? 

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GFS looks much more impressive across eastern NE.

Also looks like it intensifies *something* in SW MN maybe closer to the warm front

 

Storms going there go could track for a long ways since the parameters rapidly expand into IA towards 00z.

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mainly 4KM NAM. Sure, it gets something's right, but it often is trigger happy with a lot of things.

No model is going to be perfect.  I'm not sure if you expect models to resolve everything perfectly, but that just isn't going to happen anytime soon.  Learn what bias a model may have or where it may perform poorly and just keep that in mind when you are trying to analyze it.  There's really no sense to make blanket statements about models in that way. 

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Whoever is chasing may want/need to be up early and ready to make a quick game-time decision. Especially with some uncertainty with respect to location and timing. There could be a few lone storms that blow up real quick in the morning and with the parameters ramping up, who knows. The 00z HRRR shows a discrete cell going to town just NW of Grand Island around daybreak/11z.

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Had been pretty confident/excited about this setup until today.  The threat of morning convection blowing up definitely throws a monkey wrench into things.  The 00z HRW-NMM and HRW-ARW blow up a complex in Nebraska early in the morning, and then blasts it through much of Iowa during the day.  None of the models seem to agree on placement/timing of convection/precip at this point.  I have been planning on chasing this setup, but if I wake up early tomorrow and see a bunch of convection ongoing I may hold off.  Unfortunately gonna have to wait another 6-9hrs to make a decision whether to chase.  Just too many questions at this point.  The setup has huge potential, but also has some big potential to get screwed over by morning crapvection. 

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Had been pretty confident/excited about this setup until today.  The threat of morning convection blowing up definitely throws a monkey wrench into things.  The 00z HRW-NMM and HRW-ARW blow up a complex in Nebraska early in the morning, and then blasts it through much of Iowa during the day.  None of the models seem to agree on placement/timing of convection/precip at this point.  I have been planning on chasing this setup, but if I wake up early tomorrow and see a bunch of convection ongoing I may hold off.  Unfortunately gonna have to wait another 6-9hrs to make a decision whether to chase.  Just too many questions at this point.  The setup has huge potential, but also has some big potential to get screwed over by morning crapvection. 

I'm not overly worried about the morning convection. If anything, that could set up some outflow boundaries to utilize later in the day. Remember that we're pretty close to maximizing our amount of daylight/daytime heating in mid-June. The morning junk, if it happens, is progged to be flying into NW IA by late morning/midday. Although I wouldn't be surprised if a few cells went severe by lunchtime, I think the better time-frame for something big is mid-late afternoon. Will that area still be near the MN/IA border, or has the the threat shifted more into E NE? A lot of questions now, but I still think the ceiling is fairly high.

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NSSL WRF does little to help confidence.  Blows up a complex mid-morning in eastern Nebraska, and then plows it through Iowa through the day.  With the powerful LLJ an early firing complex of storms doesn't seem unreasonable.  How that would impact things later in the day depends on how mature it can get.  A large complex as shown by the ARW/NMM/NSSL would likely kill the better WF tor threat that would otherwise develop later tomorrow afternoon.  All speculation at this point, but I'm not feeling too confident about tomorrow anymore unfortunately.  I sure hope some of these convection allowing models are wrong.  I guess we'll find out in coming hours..

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VALID 161200Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF THE MID MO AND UPPER
MS VALLEYS EWD TO PARTS OF THE WRN GREAT LAKES...

 

...ERN HALVES OF SD/NEB EWD TO THE WRN GREAT LAKES...
STRONG LOW-LEVEL MOISTURE TRANSPORT NWD WILL BE ONGOING MONDAY
MORNING ON THE NOSE OF A 50 KT LLJ OVER THE CNTRL PLAINS.
CONSIDERABLE UNCERTAINTY REMAINS REGARDING THE POTENTIAL FOR EARLY
DAY STORM EVOLUTION AND ITS INFLUENCE ON THE PLACEMENT OF THE
EFFECTIVE WARM FRONT AND/OR OUTFLOW BOUNDARY.
DESPITE THESE
CONCERNS...STEEP MID-LEVEL LAPSE RATES IN EXCESS OF 8 DEG C PER KM
ATOP MID-UPPER 60S BOUNDARY LAYER DEWPOINTS WILL LIKELY RESULT IN A
VERY UNSTABLE AIRMASS /MLCAPE 3000 J/KG OR GREATER/ TO THE E OF THE
DRYLINE...S OF THE WARM FRONT...AND ANY EARLY DAY CONVECTIVE
OUTFLOW. THE FOCUSING OF THE LLJ INTO ERN NEB/SD AND SRN MN/NRN IA
DURING THE DAY WILL LEAD TO LARGE HODOGRAPHS...ESPECIALLY NEAR THE
WARM FRONT. DIURNALLY-GENERATED SCTD STORMS AND 40-50 KT EFFECTIVE
SHEAR WILL INCLUDE THE POSSIBILITY FOR INTENSE SUPERCELLS YIELDING A
LARGE TO VERY LARGE HAIL/WIND THREAT AND THE POTENTIAL FOR A FEW
TORNADOES /SOME PERHAPS SIGNIFICANT/.
THE APPROACH OF A 50 KT H7
WIND MAXIMUM DURING THE EVENING AND OVERNIGHT WILL SUPPORT AN
ORGANIZED WIND DAMAGE THREAT AS ACTIVITY GROWS UPSCALE AND MOVES EWD
TOWARDS THE WRN GREAT LAKES.

 

Probabilities say 10% TOR, 30% hail/wind. Possible upgrade to MDT Risk is no longer mentioned.

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Needless to say these "not knowing until nowcasting" events are becoming rather frustrating.

Overall I would say that given a blend of seasonal and modular trends, the significant TOR threat should be regarded as conditional at this point. I would bet on a couple of tornadoes, possibly a strong one, from whatever cell happens to remain discrete during the narrow late-afternoon window. The environment is really going to come down to the placement of mesoscale features.

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HRRR is finally up and running. The 4z run is complete and it shows a line of fairly tame storms lifting north through NE during the morning. Once it reaches SD by late morning it strengthens. One cell on the eastern end goes supercellular, turns right and would verbatim probably be a tornadic cell. It crosses over the SD/IA border around 1 p.m. and more storms begin to fire at 15hr, the end of the model run.

 

I think this overall evolution is very reasonable. Most data seems to target the NE/SD/IA tri-state border around midday. Things become rather unclear after that. 

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Neither the 09z HRRR nor the 06z NAM fire nest is handling the current convection well.  Both have a cluster in or around Holt County, NE at 12z lifting east-northeast through the next few hours, and not much else besides that.

 

Ironically, that area of NE is one of the only areas that's convection-free attm, but there's two broken lines of storms, both to the north all the way to east of RAP, and to the south, from the southern edge of Holt County all the way south to the KS border.

 

That makes it a bit hard to trust either's evolution of the day.

 

That said, yes, the HRRR, if believed, would make it seem like Brookings-Watertown and then east into MN might be the place to be.  And at least FSD on north and east is pretty much clear on satellite attm.

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Yes obviously the last few runs didn't initialize correctly with respect to convection... Was just talking about the solution verbatim. Still it is nice to see the northern area clear at the moment.

Sent from my iPad using Tapatalk

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Given the rather cellular nature of the current convection, I don't think it will be particularly detrimental to the late-afternoon supercell/tornado potential over portions of nern NE. Instability will likely recover quite quickly given the rather stable heights in the region. Perhaps the 10% TOR probability will be upgraded to 15% later this afternoon. Thoughts?

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Given the rather cellular nature of the current convection, I don't think it will be particularly detrimental to the late-afternoon supercell/tornado potential over portions of nern NE. Instability will likely recover quite quickly given the rather stable heights in the region. Perhaps the 10% TOR probability will be upgraded to 15% later this afternoon. Thoughts?

Important point, and a true point.  If you looks at sfc observations behind this current convection, there's very little, if any, effect from any sort of residual cold pool.  Until an organized cold pool develops, this convection in and of itself bears very little consequence to what's going to happen later.

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High res NAM and HRRR continue in total disagreement. Probably have to wait for 14Z HRRR to get some clarity. Wait, we could do some old fashioned meteorology, per the two excellent posts above!

 

NAM appears to keep 700 mb temps steady. Though not shown directly, per surface pattern, one can infer that the HRRR warms 700 mb temps through the day. There is the key. If the morning rain weakens per warming 700 mb, impressive heating and destabilization will take place. New afternoon cells will explode and become rotating supercells. Morning convection leaves outflow boundaries OFBs galore. They lift north through the day. The said supercells would cross boundaries and produce tornadoes. We need to watch trends of the ongoing rain. If it stays heavy the SPC has a good outlook.

 

If the rain weakens; the OFBs move north; dews follow; and, new supercells develop, we have a much more volatile and tornadic afternoon and evening on our hands. And perhaps north into the MSP metro by evening. I'm not chasing - no dog in the hunt - but I can see an upside surprise. Good luck and be safe!

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The NMM/ARW WRF models are split by their usual biases.  NMM has convection forming late afternoon/early evening in ern NE/wrn IA, while ARW fails to initiate.

 

    Assuming you're talking about the hi-res windows, be careful discussing biases.    There was a major hi-res window operational upgrade last week.     Both are now initialized by the RAP, both are now higher resolution, the ARW got a major update, and the NMM was actually replaced by the NMMB.

        http://www.nws.noaa.gov/os/notification/tin14-16hiresw_aaa.htm

 

     It's very possible that some biases from the old system remain, but one certainly can't apply old NMM biases to the NMMB.

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The storm scale modeling today is almost comical. There is like a 500 mile difference on where they setup the most significant activity. My favorite is the HRW-ARW which shows the most significant UH track of the day being just to the north of St. Louis. Um...what?

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I was going to chase the WF portion, as NE is too far for me to chase and make it back for work tomorrow.  However, the morning convection has muddled the WF setup IMO.  The elevated complex in eastern NE will likely be maintained by the impressive LLJ, and will probably merge with that area of convection in east SD.  That will then plow eastward in similar fashion to the 00z NSSL WRF.  Due to the amount of shear there could be some strong mesovorticies along the leading edge that could aid in significant wind threat.  Really am surprised they didn't hatch the wind threat. 

 

The best chasing op IMO today is along the dryline in central NE.  This area will remain untouched by the morning convection, and the dryline should be enough to fire off sups by late afternoon.  Hopefully NE can give some redemption to chasers today, for those who are out there. 

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    Assuming you're talking about the hi-res windows, be careful discussing biases.    There was a major hi-res window operational upgrade last week.     Both are now initialized by the RAP, both are now higher resolution, the ARW got a major update, and the NMM was actually replaced by the NMMB.

        http://www.nws.noaa.gov/os/notification/tin14-16hiresw_aaa.htm

 

     It's very possible that some biases from the old system remain, but one certainly can't apply old NMM biases to the NMMB.

Thanks for the update!  I believe it was a talk in Atlanta a few months ago that discussed the overconvective bias of the NMM and underconvective bias of the ARW.  I was taking Ph.D. prelims last week and wasn't aware of the upgrade.

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