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janetjanet998

May 27-29 Severe Potential

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This is shaping up to be a concerning day for the metro. The convection out there this morning doesn't seem like it'll keep the warm front well south. Latest guidance gets the warm front to or north of the I-88 corridor later. Aside from the immediate lakeshore possibly being helped by onshore winds, Rockford area to interior parts of metro to northwest Indiana could be under the gun.

 

In addition to the strong directional shear/SRH maximized near the front, as has been noted, very high levels of 0-3km CAPE are being progged in forecast soundings with values of 100-200+ j/kg (50+ is typically favorable for tornadoes). Bunkers right moving storm motion vectors are out of the west-northwest, which would parallel the west northwest to east-southeast oriented warm front and maximize ingestion of streamwise vorticity. Observational trends to say the least are very important over the next few to several hours, chiefly all important position of the warm front. Wouldn't be surprised if SPC needs to add a MDT in one of the updates.

 

 

 

 

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Some (myself included) are finding the dense clustery convection (even with strong UH streaks) apparent on the HRRR and 3KM NAM concerning for chaseable tornado potential. I'll re-post what I just posted on ST Discord:

I admit I often fail to do this enough, so let's go through some of the factors that usually lead to the convective mess/quick upscale growth the CAMs are hinting at.

Low-mid level VBV? Not really seeing it.

Shear vectors parallel to the initiating boundary? Not that I'm seeing.

Too much forcing for too little capping? Possibly.

Any others I'm missing?

Although regarding the forcing, isn't that usually a problem with a very strong synoptic system? Per mesoanalysis, this SFC low should be deepening with time (a positive if you want storms), but not getting TOO deep (~1000MB), which might actually lead to a higher significant tornado threat.

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Would expect best chances of tornadic cells about 30-50 miles south of ORD as remnants of occluded front interact with Lake Michigan and extensive east winds over northern IN southern MI to set up barrier to northward advection of tropical air mass, max risk somewhere around Galesburg to Streator to Kankakee. 

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Stay safe boys and good luck! I look to be close to ground zero. Grilling in the backyard. I’ll grab some pics if anything pops.

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Thinking about heading out here soon. If anyone wants to meet up somewhere just send a DM. Should be a nice event unfolding. 

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1 hour ago, CheeselandSkies said:

Some (myself included) are finding the dense clustery convection (even with strong UH streaks) apparent on the HRRR and 3KM NAM concerning for chaseable tornado potential. I'll re-post what I just posted on ST Discord:

I admit I often fail to do this enough, so let's go through some of the factors that usually lead to the convective mess/quick upscale growth the CAMs are hinting at.

Low-mid level VBV? Not really seeing it.

Shear vectors parallel to the initiating boundary? Not that I'm seeing.

Too much forcing for too little capping? Possibly.

Any others I'm missing?

Although regarding the forcing, isn't that usually a problem with a very strong synoptic system? Per mesoanalysis, this SFC low should be deepening with time (a positive if you want storms), but not getting TOO deep (~1000MB), which might actually lead to a higher significant tornado threat.

I think you're right to have some concern about perhaps too much storm coverage.  If it doesn't knock down the tornado potential then it could at least make it a bit messy for chasing.  How long it takes to transition to cluster/MCS is a question.  

 

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69/64 in DKB with a sizable slug of storms to move through. Hopefully this won’t hold up the warm front, would like to see it push north of 88 for some hyper local chasing (familiarity of area/terrain) makes it much more enjoyable)

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Kind of like Kankakee to Logansport to Columbus as the area today. I don’t buy it surging as far north as they think but we will see

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10% hatched tornado area expanded east to just west of Ft. Wayne on new day 1 otherwise no other changes.

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A subtle shift east with the 10% hatched tor, with north extent holding firm, but now effectively encompassing all of Cook County.

Sent from my SM-N960U using Tapatalk

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10 hours ago, hlcater said:

Note the extremely favorable 200+ 0-3km CAPE on many forecast soundings... one of the single biggest things I think this setup has going for it. 

Anyone have an update on this?  

if this is confirmed  true  then low topped mini spinners look likely.... perhaps evolving out of that blob of precipitation over SE IA

edit: back after going dark for 12+ hours LOL

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I don’t see how the precip in central IL and SE Iowa won’t reduce this opportunity?. Seems that every chance we’ve had recently has been killed by morning convection.  Any thoughts around this?

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21 minutes ago, kevlon62 said:

A subtle shift east with the 10% hatched tor, with north extent holding firm, but now effectively encompassing all of Cook County.

Sent from my SM-N960U using Tapatalk
 

Even LOT was skeptical about the northward placement per the overnight afd.  Tornado threat is not zero for Cook, but I think about the southern/western half of the county could have a higher risk than farther north.

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Will be interesting to see if the stuff by Lasalle can go severe eventually or if we'll have to wait for more development.

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12 minutes ago, RyanDe680 said:

I don’t see how the precip in central IL and SE Iowa won’t reduce this opportunity?. Seems that every chance we’ve had recently has been killed by morning convection.  Any thoughts around this?

That chunk of storms is hauling ass. We will see how it plays out, but they should be well gone in a hour 

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13 minutes ago, RyanDe680 said:

I don’t see how the precip in central IL and SE Iowa won’t reduce this opportunity?. Seems that every chance we’ve had recently has been killed by morning convection.  Any thoughts around this?

the SE IA disturbance is likely the trigger for the storms soon ahead  of it or within it...in these set ups, very high 0-3 km CAPE , sometimes mini sups may develop within it...watch for higher reflectivity cores  from DVN radar as a sign

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14 minutes ago, janetjanet998 said:

the SE IA disturbance is likely the trigger for the storms soon ahead  of it or within it...in these set ups, very high 0-3 km CAPE , sometimes mini sups may develop within it...watch for higher reflectivity cores  from DVN radar as a sign

If that is where our sups are coming from, storm it’s going to be a nightmare to chase. 

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4 minutes ago, SchaumburgStormer said:

If that is where our sups are coming from, storm it’s going to be a nightmare to chase. 

ok..looks like there are building now around MLI..if I were chasing a would be in between galesburg and MLI  right now as staging 

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7 minutes ago, Natester said:

FYI, there's an embedded supercell with a confirmed tornado in Floyd county, Iowa.

VERE WEATHER STATEMENT  
NATIONAL WEATHER SERVICE LA CROSSE WI  
1242 PM CDT MON MAY 27 2019  
  
IAC067-089-131-271815-  
/O.CON.KARX.TO.W.0008.000000T0000Z-190527T1815Z/  
MITCHELL IA-HOWARD IA-FLOYD IA-  
1242 PM CDT MON MAY 27 2019  
  
...A TORNADO WARNING REMAINS IN EFFECT UNTIL 115 PM CDT FOR  
SOUTHEASTERN MITCHELL...SOUTHWESTERN HOWARD AND NORTHEASTERN FLOYD  
COUNTIES...  
      
AT 1241 PM CDT, A CONFIRMED TORNADO WAS LOCATED 2 MILES WEST OF   
COLWELL, OR 10 MILES SOUTHEAST OF OSAGE, MOVING NORTHEAST AT 40 MPH.  
  
HAZARD...DAMAGING TORNADO.  
  
SOURCE...WEATHER SPOTTERS CONFIRMED TORNADO. DAMAGE TO HOUSES HAS   
         BEEN REPORTED NORTH OF CHARLES CITY.  

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MESOSCALE DISCUSSION 0831  
NWS STORM PREDICTION CENTER NORMAN OK  
1250 PM CDT MON MAY 27 2019  
  
AREAS AFFECTED...PORTIONS OF EASTERN IA...NORTHERN AND CENTRAL IL  
AND NORTHERN IN  
  
CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY   
  
VALID 271750Z - 271915Z  
  
PROBABILITY OF WATCH ISSUANCE...95 PERCENT  
  
SUMMARY...SEVERE THUNDERSTORMS WITH A THREAT OF TORNADOES (SOME  
POTENTIALLY STRONG), LARGE HAIL AND DAMAGING WINDS WILL INCREASE  
OVER THE NEXT COUPLE OF HOURS. WATCH ISSUANCE IS LIKELY.  
  
DISCUSSION...A WARM FRONT IS RAPIDLY LIFTING NORTHWARD AND DRAPED  
ACROSS NORTHERN IL INTO SOUTHERN/CENTRAL IN AS OF 17Z. DEWPOINTS  
WILL CONTINUE TO CLIMB INTO THE MID AND UPPER 60S THIS AFTERNOON AND  
MLCAPE VALUES WILL STEADILY INCREASE TO AROUND 1500-2000 J/KG OVER  
THE NEXT 2-4 HOURS. A SHORTWAVE TROUGH CURRENTLY MIGRATING  
EAST/NORTHEAST ACROSS IA/MO WILL PROVIDE LARGE-SCALE FORCING, WHILE  
A COUPLE OF MCVS FROM MORNING CONVECTION WILL RESULT IN MORE SUBTLE  
FORCING ACROSS THE REGION. AREAS DOWNSTREAM OF THESE MCVS AS WELL AS  
ALONG THE WARM FRONT WILL BE A FOCUS FOR THUNDERSTORM DEVELOPMENT  
AND ORGANIZATION IN THE NEXT 1-2 HOURS FROM EASTERN IA INTO NORTHERN  
AND CENTRAL IL. ADDITIONAL STORMS ARE EXPECTED TO DEVELOP ALONG THE  
NORTHWARD ADVANCING WARM FRONT ACROSS CENTRAL INTO NORTHERN IN. THE  
TIMING OF CONVECTIVE INITIATION FURTHER EAST ACROSS IN IS A BIT MORE  
UNCERTAIN, BUT SEVERE STORMS ARE EXPECTED BY 21-22Z.    
  
18Z RAOB FROM DVN SHOWED CAPPING JUST BELOW 850MB. WITH THE INCOMING  
SHORTWAVE, TEMPERATURES ALOFT ARE EXPECTED TO COOL AND WITH  
CONTINUED HEATING AND MOIST ADVECTION, THIS CAP IS EXPECTED TO  
QUICKLY ERODE BY MID AFTERNOON. IN FACT, 18Z RAOB FROM ILX IS  
UNCAPPED WITH STEEP MIDLEVEL LAPSE RATES NOTED IN ADDITION TO STEEP  
LOW LEVEL LAPSE RATES AND A MEAN MIXING RATIO APPROACHING 14 G/KG.  
THIS THERMODYNAMIC ENVIRONMENT COMBINED WITH FAVORABLE VERTICAL  
SHEAR WILL SUPPORT SUPERCELLS. THE VERY MOIST BOUNDARY LAYER  
COMBINED WITH IDEAL LOW LEVEL HODOGRAPHS (NOTED IN DVN RAOB) SHOULD  
LEAD TO TORNADO POTENTIAL SUPPORTIVE OF AT LEAST A COUPLE OF STRONG  
TORNADOES.   
  
A TORNADO WATCH WILL LIKELY BE NEEDED BY 19Z ACROSS PARTS OF FAR  
EASTERN IA INTO NORTHERN/CENTRAL IL. UNCERTAINTY IN TIMING FURTHER  
EAST INTO IN MAY RESULT IN LATER TORNADO WATCH ISSUANCE, BUT EXPECT  
ADDITIONAL WATCH ISSUANCE BY 21Z.  

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ULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE QUAD CITIES IA/IL  
108 PM CDT MON MAY 27 2019  
  
THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  SOUTHERN HENRY COUNTY IN SOUTHEASTERN IOWA...  
  EASTERN VAN BUREN COUNTY IN SOUTHEASTERN IOWA...  
  NORTHWESTERN LEE COUNTY IN SOUTHEASTERN IOWA...  
  
* UNTIL 200 PM CDT.  
      
* AT 108 PM CDT, A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO  
  WAS LOCATED OVER BENTONSPORT/VERNON, OR NEAR KEOSAUQUA, MOVING  
  NORTHEAST AT 35 MPH.  

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