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Chicago WX

2013 GLOV Severe Weather Discussion

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I know next to nothing about medium range severe weather possibilities/threats, but thought it might be nice for those in the know to discuss the medium range pertaining to that in this thread. Might be a nice thing to look back on at a later time, to see how the models and hobbyists handled things...correctly or incorrectly.

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my body is ready

 

For what? :P

 

As for myself I hope to get in a good chase this year, something on Wed or Thursday (only days off) within 400 miles of here.

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The last operational 0z Euro shows an amplifying a low tracking right over Chicago at 168 hours.  I have no idea if that's consistent with other runs and ensemble members though.  GFS has had no consistency at that range.

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A large trough moving out of the western US this weekend and into the first half of next week is expected to combine with weakening high latitude blocking and allow for ridging to develop over the southeastern US, with much warmer weather attempting to advance into our subforum, especially closer to the Ohio River:

 

post-525-0-53352600-1365015498_thumb.png

 

A quick glance at the operational GFS and Euro suggest that the potential for a fairly strong 500mb jet, on the order of 60-70 knots, to impinge on the northern and western portions of any warm-sector early next week:

 

post-525-0-87261000-1365015648_thumb.gif

 

The op 12z GFS and op 0z Euro both show the potential for 55-60F dewpoints to move northward into the Ohio Valley and potentially lower lakes Monday-Tuesday if a stronger wave of low pressure can develop, however both sets of ensembles do not appear to be as robust in low pressure development, which not only allows the baroclinic zone/front to sit closer to the Ohio River early next week but also minimizes moisture return south of the front.

 

So, although the severe threat is non-zero in portions of the sub-forum Monday-Wednesday, the best chance for any severe is likely along if not south of the Ohio River. North of the Ohio River, considerability uncertainty exists regarding whether or not a strong enough wave of low pressure will develop to pull the front and sufficient moisture northward for severe weather to occur. Given we are still in a strong blocking regime with the AO not expected to break into positive territory until the middle portions of next week, and that it appears the trough may maintain a positive tilt through the central and eastern US next week as it moves east, I would lean towards a more suppressed solution Monday-Wednesday with any waves of low pressure, however there is still time for change.

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Have had similar thoughts to OHweather, but the 00z GFS pretty much shows what could happen if there's a mechanism to surge the warm front far enough north. 60 degree dew points get to basically the Wisconsin border Tuesday afternoon and early evening ahead of the cold front. With pretty impressive wind fields/shear, there would likely be a severe risk with that set-up. 2m temps on the GFS are close to dew points, so instability is not all that impressive, but you'd think with 60 dews in April, surface temps would be warmer than low-mid 60s unless we're completely socked in with clouds. Here's a sounding and hodograph over northeastern IL: 

 

GFS_3_2013040400_F144_42.0000N_88.0000W.

GFS_3_2013040400_F144_42.0000N_88.0000W_

 

On the other hand, the 00z ECMWF doesn't have a surface low to bring the warm front north Tuesday, so the severe threat would likely be much farther south: 

 

f144.gif

 

It'll be interesting to see how this unfolds. Still lots of ensemble spread, though it looks like there's at least a few GFS members that bring a surface low into the western lakes. 

 

Day 6 SPC Outlook covers the differences between the 2 scenarios, but either way, mentions potential for significant severe and includes Mid MS Valley in the text: 

 

 

...TUESDAY/D6 TO THURSDAY/D8 - ERN OK/ARKLATEX INTO THE MIDDLE AND   LOWER MS VALLEY...   AFOREMENTIONED COLD FRONT DEPICTED BY GFS IS FORECAST TO SURGE SWD   AND WILL BECOME A PRIMARY FOCUS FOR CONVECTION FROM NRN IL INTO MO   AND OK...LINKING WITH THE DRYLINE OVER N CNTRL TX. BY   TUESDAY...SUBSTANTIAL BOUNDARY LAYER MOISTURE WILL BE IN PLACE WITH   UPPER 60S F DEWPOINTS AHEAD OF THE FRONT.       MEANWHILE...THE ECMWF SOLUTION KEEPS THE SYNOPTIC FRONT STATIONARY   ACROSS SRN NEB INTO NRN IL/IND DURING THE DAY ON TUE...WITH THE   DRYLINE FROM CNTRL KS INTO OK AND CNTRL TX. THIS MODEL ALSO   INDICATES SUBSTANTIAL MOISTURE AND INSTABILITY POTENTIAL FROM   KS/OK/TX INTO THE LOWER MS VALLEY.      GIVEN THESE MODEL DIFFERENCES...PREDICTABILITY IS TOO LOW FOR AN   AREA ON TUE/D6...ALTHOUGH THERE IS THE POTENTIAL FOR SIGNIFICANT   SEVERE INCLUDING TORNADOES. THE THREAT SHOULD PERSIST INTO WED/D7   ACROSS THE LOWER MS VALLEY. AREAS ARE LIKELY TO BE INTRODUCED AS   PREDICTABILITY INCREASES IN SUBSEQUENT OUTLOOKS.

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Yeah the 00z GFS definitely looks interesting for northern IL and southern WI.  Closed surface low coming out of eastern Iowa with winds backed due southerly over IL.  Nice turning with height as well with winds at H5 west-southwesterly.  Dews shown to be in the 60s might not be overdone considering the feed from the gulf wide open for several days before.  If clouds/precip don't mess this up, it could be a decent first good setup for this area.  This is taking the 00z GFS verbatim though, and like pointed out above the Euro was way different.  Chances are the 12z GFS coming in right now will end up different as well.  Something to watch in the future though...

 

EDIT:  Already things have changed lol.  12z GFS shows Tue setup much further southwest over Kansas still.  Looks like a great setup down there.

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Tue could still be an interesting setup along the warm front over southern Iowa/northern Missouri per 12z GFS if something can fire.  Soundings look pretty sweet in that area and with the warm front hanging around that only improves things.  The setup will change 12 times by the time we get there, but worth pointing out I guess for conversational purposes lol.

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At least elevated convection is looking possible for the Chicago area up into southern lower MI on Wednesday.  I'd really love to get into the warm sector but it isn't looking likely for anyone north of I-94.  So much stratus and precip around it will probably be stuck in the 40s most of the time even with 850 temps pushing close to +10C.  Kinda annoying.  Will have to wait for the real warmup later on.

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day48prob.gif

 

 

DAY 4-8 CONVECTIVE OUTLOOK     

NWS STORM PREDICTION CENTER NORMAN OK    0354 AM CDT FRI APR 05 2013       

VALID 081200Z - 131200Z       

 

...DISCUSSION...   

...SEVERE WEATHER APPEARS LIKELY EARLY NEXT WEEK FROM THE CNTRL/SRN    PLAINS TO THE MID/LOWER MS VALLEY...      

 

  WHILE RICH GULF MOISTURE HAS BECOME CONFINED TO THE SWRN PORTION OF    THE BASIN IN THE WAKE OF A COLD FRONT THAT HAS REACHED THE YUCATAN    PENINSULA...AIR MASS MODIFICATION WILL OCCUR THIS WEEKEND AND    ESPECIALLY EARLY NEXT WEEK AHEAD OF AN AMPLIFIED UPPER-LEVEL TROUGH    OVER THE WEST. THE WRN TROUGH WILL EJECT INTO THE CNTRL CONUS BY    MID-WEEK AS A POTENT MID-LEVEL JET STREAK ROUNDS THE BASE OF THE    TROUGH. BY THIS TIME...SEASONABLY RICH GULF MOISTURE WILL BE PRESENT    ALONG THE DRYLINE AND EVENTUAL COLD FRONT THAT WILL PUSH EWD TOWARDS    THE MS VALLEY. WITH SEVERAL DAYS OF MOISTURE RETURN OCCURRING    BENEATH A STOUT EML...A MODERATE TO STRONGLY UNSTABLE AIR MASS WILL    LIKELY DEVELOP.      

 

DESPITE AVERAGE DIFFERENCES BETWEEN MODELS WITH REGARD TO    TIMING/PLACEMENT OF THE KEY SYNOPTIC FEATURES BY D5-6...INCREASING    FORCING FOR ASCENT ALONG WITH STEEP MID-LEVEL LAPSE RATES AND    STRENGTHENING DEEP-LAYER SHEAR SHOULD RENDER A SETUP FAVORABLE FOR    POTENTIALLY SIGNIFICANT AND WIDESPREAD SEVERE WEATHER DURING THIS    TIME FRAME. GREATEST DISCRETE SUPERCELL POTENTIAL WITH PRIMARILY    VERY LARGE HAIL AND TORNADOES SHOULD EXIST ON D5 AHEAD OF THE    DRYLINE. AS A PACIFIC COLD FRONT MERGES WITH THE DRYLINE...
AN    EXTENSIVE SQUALL LINE SHOULD FORM AND DEVELOP EWD TOWARDS THE MS    VALLEY WITH PRIMARY RISKS BECOMING DAMAGING WINDS AND TORNADOES ON    D6.
PRIOR TO D5...A LOCALIZED BUT ENHANCED RISK FOR VERY LARGE    HAIL/FEW TORNADOES SHOULD EXIST NEAR THE DRYLINE/WARM FRONT    INTERSECTION EXPECTED TO BE INVOF NWRN KS ON MON EVENING.

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Hoping to chase Wednesday since I'm off, though concerned about SPC discussion mentioning expected squall line evolution. 00z Euro verbatim would be good from warm front action up to central IL and IN, and it appears SPC hedged towards the Euro and its ensembles in its D6. Now the 12z op GFS, which warm sectored much more of the subforum on Wednesday in its 00z and 06z runs, shifts everything to Tuesday. Until the upper level system gets on shore, I'm sure we'll see more significant shifts in the guidance.

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Hoping to chase Wednesday since I'm off, though concerned about SPC discussion mentioning expected squall line evolution. 00z Euro verbatim would be good from warm front action up to central IL and IN, and it appears SPC hedged towards the Euro and its ensembles in its D6. Now the 12z op GFS, which warm sectored much more of the subforum on Wednesday in its 00z and 06z runs, shifts everything to Tuesday. Until the upper level system gets on shore, I'm sure we'll see more significant shifts in the guidance.

Some very nice soundings off the 12z GFS for portions of MO/IL/IN on Tues.

As you mention though there was yet another drastic shift. I'll stick with the ECMWF for now.

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Some very nice soundings off the 12z GFS for portions of MO/IL/IN on Tues.

As you mention though there was yet another drastic shift. I'll stick with the ECMWF for now.

Probably prudent unless the EC were to shift into the GFS camp. From the C/W thread, sounds like the GGEM is Euro like but haven't checked it out yet. Also pulling for the slower solution so there's potentially something to chase Weds lol. 

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Probably prudent unless the EC were to shift into the GFS camp. From the C/W thread, sounds like the GGEM is Euro like but haven't checked it out yet. Also pulling for the slower solution so there's potentially something to chase Weds lol. 

The 12z GGEM is pretty much a middle of the road solution.

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I really want the 12z GFS to be correct.  Not just for the sake of severe chances, I just crave the feeling of warmth and humidity on my skin.  It's been a long time. 

 

GFS is the starry eyed enthusiastic kid.  ECMWF is the grouchy realist/pessimist who usually turns out to be right.  Ugh.

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The 12z GGEM is pretty much a middle of the road solution.

Agree with what you said in the C/W thread, with the operational GFS struggling with the teleconnections, probably should take it with a grain of salt for now. The GFS/MRF ensembles are favoring keeping the -NAO blocking in place until after the system passes, so slower and farther south ala the Euro is probably the way to go.

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Agree with what you said in the C/W thread, with the operational GFS struggling with the teleconnections, probably should take it with a grain of salt for now. The GFS/MRF ensembles are favoring keeping the -NAO blocking in place until after the system passes, so slower and farther south ala the Euro is probably the way to go.

And now the 18z run takes a sig step back.

 

It's going to be an interesting few days of model watching, mostly because the lack of great chase opportunity since 4/14.

 

Hopefully it works out in the end for you to chase some action on Wed.

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And now the 18z run takes a sig step back.

It's going to be an interesting few days of model watching, mostly because the lack of great chase opportunity since 4/14.

Hopefully it works out in the end for you to chase some action on Wed.

The 12z GFS probably will end up having been a toss run. Agreed, I'm sure I'll be following every run from here on out, as will a lot of other people. Are you chasing any of the days next week?

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The 12z GFS probably will end up having been a toss run. Agreed, I'm sure I'll be following every run from here on out, as will a lot of other people. Are you chasing any of the days next week?

Tues is my only day off...So current plans are to fly down to OKC for the day.

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Tues is my only day off...So current plans are to fly down to OKC for the day.

Couldn't have timed it any better it looks like, though the soundings for Monday evening are pretty insane if the cap can be broken.

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I think Tue and maybe more likely Wed holds some potential around here but best to keep optimism reserved. If nothing else, this should be a good "tune up" event for later in the season.

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I think Tue and maybe more likely Wed holds some potential around here but best to keep optimism reserved. If nothing else, this should be a good "tune up" event for later in the season.

 

Yeah I do agree there could be a squall line potential up this way if the low can get far enough north, though I wouldn't be shocked at a conditional tornado potential as well along the warm front.

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Could be some decent storms in Iowa Sunday.  Strong cold front with strong forcing moving in.  Deep moisture should be sorely lacking, but just enough for some meager instability.  NAM shows around 1000j/kg, but that's likely too robust.  Still expect a nice squall line to develop in central Iowa and rake eastward. 

 

wrf.maxdbz.0060.gif

wrf.cape.0058.gif

 

Sounding for MLI 00z. 

wrf.skewMLI.0060.gif

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